Recent Advances in Additive Manufacturing: A Review of Current Developments and Future Directions

Abstract

Additive manufacturing (AM), often referred to as 3D printing, has seen significant advances over the last few years. Through extensive research covering a wide range of industries from automotive and aerospace to healthcare, AM comes with the advantage of reduced manufacturing costs and ease of transition from design to real prototype. This review paper navigates the landscape of the AM process to highlight the latest findings in terms of process, materials, and applications by analyzing publications between 2022 and 2025. A particular focus is given to the integration of new materials including high-performance polymers and bio-based composites, types of printing materials that can enhance the performance and durability of 3D printing processes. In addition, the paper examines advances in printing technologies, including multi-material and large-format printing, as well as the integration of artificial intelligence for process optimization and quality control. Considering these advances, critical challenges such as the productivity, high cost, limited material options, and ethical concerns over intellectual property are also addressed. By synthesizing current trends and assessing future directions, while considering a critical view, this study aims to inform researchers and industry stockholders about the evolving additive manufacturing landscape and the opportunities and obstacles on the horizon.

1. Introduction

Additive manufacturing represents a transformative alternative to traditional manufacturing processes that enables the layer-by-layer manufacturing of complex geometries directly from digital models prepared with Computer Aided Design (CAD) softwares. This means that the production of a prototype is made easy as soon as the design is carried out with this type of software in an efficient and precise manner. The AM process is in line with traditional subtractive manufacturing methods, certainly machining using CNC machines, which often involve cutting materials from solid blocks or sheets of metal. In fact, the ability of AM to produce complex parts from 3D models with minimal waste has attracted the interest of a variety of industries, including aerospace, automotive, biomedical, healthcare and consumer goods. The application of AM has significantly expanded thanks to continuous research and development, which have improved materials, technologies, and processes over the past few years [1,2].

The capabilities and limits of the additive manufacturing process are directly influenced by the materials utilized. The earliest materials used in AM were metal powders, namely titanium and stainless steel, thermoplastics like Acrylonitrile Butadiene Styrene (ABS) for Fused Deposition Modeling (FDM), and photopolymers for stereolithography. These materials served as the foundation for many of the cutting-edge materials currently employed in additive manufacturing today. To improve the efficiency of the AM process, much research has been carried out to test new printing materials such as high-performance composites, metals, ceramics, and polymers. For instance, eco-friendly and bio-based materials have become very popular in 3D printing due to consumer need for greener and more sustainable products [3].

Polymers with high printing abilities, such as polylactic acid (PLA) and thermoplastic polyurethane (TPU), are usually used in 3D printing for wide range of applications [4]. In contrast, thinking to improve the mechanical proprieties and functionality of 3D-printed parts, the integration of advanced composites that layer multiple materials leads to new opportunities in AM such as applications for energy storage and conversion devices [5]. For instance, to the development of 3D printing technology, the possibility to print out multicolor materials using multi-extruders made the process able to produce more complex and useful products. In addition, the use of artificial intelligence (AI) and machine learning in the processing of the 3D-printed components has demonstrated its potential to enhance the production efficiency and precision. By facilitating real-time monitoring, these technologies help printers adapt to changes in the environment and minimize production faults. According to some studies, AI-driven algorithms can evaluate huge datasets and predict ideal printing conditions to guarantee better results and less material waste [6,7].

The AM’s scalability attracted the attention of much recent research. Innovative ideas to increase the scale of printing have been presented in many fields such as infrastructure buildings with the aim to achieve better productivity with lead times, which is key to expanding AM’s applicability in mass production [8,9]. These innovations are significant to industries that require lead times and high-volume production while retaining the customization benefits offered by AM.

In contrast to these advancements, several critical challenges need more focus in the future to increase the flexibility of this process. High capital costs associated with AM equipment, certainly with respect to a larger scale or using new materials, can deter small and medium-sized enterprises (SMEs) from integrating AM technologies into their production lines. Additionally, the availability of these new printing materials and the slowness of several additive manufacturing technologies restrict widespread applications in various sectors [10]. Post-processing challenges also present obstacles, as most AM technologies require additional steps of post-processing after 3D modeling to achieve the desired quality, which add more time and cost to the overall manufacturing process [11]. Furthermore, ethical and intellectual property concerns need attention as the use of 3D printing technologies raises questions about ownership rights and the potential for misuse. The ability to make replicated products using these technologies is very easy when a 3D modeling software’s and scanners are available, which can lead to unauthorized reproductions and infringement on patents; this can be a great concern within industrial applications [12]. Researchers and industry stakeholders must navigate these complex issues to foster a responsible and sustainable environment for additive manufacturing.

The future of additive manufacturing techniques is very promising, certainly with the integration of new eco-friendly, biodegradable materials thinking of sustainability within this manufacturing process and reducing waste [13]. These initiatives align with global sustainability needs and reflect consumer awareness and demand for environmentally friendly practices. Additionally, the revolution in decentralized production networks triggered by digital manufacturing systems such as 3D printers and CNC machines can reduce transportation costs and therefore carbon footprint by facilitating localized production [14].

Another promising growth area in additive manufacturing is bioprinting, which uses bio-based materials that can be used in personalized medical components and tissue engineering applications in healthcare. Deep research on the use of printable biomaterials and the possibility to produce living cells could lead to revolutionary solutions in regenerative medicine with the help of AM’s techniques [15].

In conclusion, remarkable progress has been remarked in the AM process during recent years, thanks to advances in technologies used, integration of innovative materials, and the exploitation of new applications that have captured the attention of industries worldwide. On the other hand, major challenges such as material printability, quality, high cost, productivity, and ethical concerns should be addressed to fully leverage the potential of this transformative process. By analyzing the latest findings in the field and critically assessing their implications to the improvement of AM processes and their limitations, this review paper aims to contribute to the understanding of the current additive manufacturing landscape and stimulate thinking about its future, thus paving the way for innovative and responsible applications in various sectors.

2. Current Developments in Additive Manufacturing

2.1. Overview of Existing AM Technologies

The current developments in the AM process led to the use of several technologies such as Fused Deposition Modeling (FDM), stereolithography (SLA), Selective Laser Sintering (SLS), Digital Light Processing (DLP), Selective Laser Melting (SLM), Binder Jetting, Material Jetting, Direct Ink Writing (DIW), and Additive Friction Stir Deposition (AFSD) plotted in Figure 1, Figure 2, Figure 3, Figure 4, Figure 5, Figure 6, Figure 7, Figure 8 and Figure 9. Each of these technologies has unique principles, applications, and limitations that fit specific manufacturing needs.

The FDM principle plotted in Figure 1 is executed by an extruding thermoplastic filament, usually stocked in coils, through a heated nozzle to create layers that solidify upon cooling on a heated build platform, moving with the extruder through three axes of movements. FDM is widely used for small-scale prototyping, for educational purposes, some consumer products [16], and low-rate production [17]. As advantages, FDM reduces waste in contrast with subtractive manufacturing processes; it is usually safer when processed with no toxic resins or solvents during fabrication, reduced post-processing, several parts with no special storage beyond typical room temperature for common filaments, and rapid design iteration for validation and customization. However, FDM faces several technological limitations, which include surface finish and dimensional accuracy due to layer-by-layer deposition and stair-stepping. The anisotropic mechanical properties of the materials used incorporate lower strength in the Z direction, warping, and shrinkage, particularly for large parts or parts made from ABS, as well as the need to use support structures that increase material usage and post-processing. Adjustments to thermal conditions such as printing temperatures, cooling, and ambient conditions can cause certain defects such as delamination, while a limited range of high-performance materials restricts thermal, chemical, and mechanical capabilities. Print speed is generally a trade-off with the quality of the manufactured parts, the nozzle extrusion suffering from clogging or gaps, and dimensional stability potentially requiring significant calibration and compensation. Post-processing (sanding, sealing, annealing, or smoothing) is commonly needed to meet functional tolerances, and moisture sensitivity in some filaments further complicates manufacturing and storage.

The FDM method has been used to manufacture a number of materials over the years, including polymers, metal powder, ceramics, and composites [18]. Recently, Mani et al. [19] and Gholipour et al. [20] have investigated the material optimization for better mechanical properties of manufactured parts in FDM; they emphasized the importance of printing parameters and filament composition for strength and durability. As an environmental study, Sola et al. [21] suggested that filaments made from recycled materials can remarkably reduce the carbon footprint of 3D-printed parts and lower the energy used. Mattew et al. [22] have confirmed that FDM recycling of polymer composites can be optimized to achieve substantial sustainability advantages in terms of environmental impact and material preservation. This technique of 3D printing has attracted great attentions in recent environmental impact investigations that highlight critical sustainability considerations. In fact, the selection of printable materials significantly affects the environmental outcomes. Biodegradable materials like PLA generate less waste in contrast to non-biodegradable materials like ABS, which raises concerns regarding the long-term environmental effects, certainly when unused products will be thrown out [23]. In terms of energy consumption, lifecycle assessments have indicated that the localized production using the FDM technique can be more sustainable compared to conventional manufacturing methods, such as machining, despite its energy requirements [24]. However, gas emissions during this process, such as ultrafine particles and volatile organic compounds, raise respiratory risks by contaminating the indoor air, which increase the need of proper ventilation in FDM workplace [25]. An existing need for a deep focus to the development of sustainable materials, including recycled filaments and bio-based materials, could enhance the eco-friendliness of FDM practices [26]. Collectively, these findings highlight the potential for FDM to contribute positively to sustainability when paired with responsible material choices and advancements in practices.

The literature reveals a substantial growth in the use of the FDM process in various applications across multiple fields. Several studies provide comprehensive experimental validation while others focus on preliminary testing. The strengths lie in the diversity of applications tested and the systematic approach to parameter optimization in many studies. However, there are limitations in terms of long-term durability testing of FDM parts and standardization of test protocols across different applications. The mechanical properties of parts manufactured using the FDM technique remain a major issue for structural applications, although significant improvements have been achieved through material innovations and process optimization. The anisotropic nature of FDM parts remains a challenge that researchers are addressing through various approaches, including hybrid fiber reinforcement and heat treatment methods.

Figure 1. Principle of Fused Deposition Modeling (FDM) [27].

Figure 1. Principle of Fused Deposition Modeling (FDM) [27].

SLA as a 3D printing technique uses a UV laser source to polymerize liquid resin layer per layer, transforming it into a solid object. This technique plotted in Figure 2 is applied for highly detailed prototypes, dental prothesis and jewelry production. It has several advantages, such as high precision and excellent surface finish. But on the other hand, it has drawbacks such as the high cost of resins, and it requires extensive post-processing. Mechanical properties of finished products also raise a problem during the use of this 3D printing technique.

Recent advancements in SLA 3D printing have shown promising enhancement in the productivity of the process and the quality of finished products. Yüceer et al. [28] found that the use of a novel photopolymer resin could improve the quality of printed models with reducing the post-processing time, which indicated a shift toward more efficient material usage. Similarly, Kadauw [29] tested the use of machine learning algorithms in SLA processes to dynamically optimize the printing parameters. The procedure presented leads to the reduction in defects and to higher fidelity prints as well as enhancing mechanical strength. Expanding on these developments, Guttridge et al. [30] explored the use of new biocompatible resins in some medical applications, emphasizing the need for regulatory considerations in their applications. Additionally, Gao et al. [31] presented a dual-curing procedure that significantly reduced processing time while maintaining structural integrity. However, while these investigations have presented exciting innovations, key critics argue that the focus on increasing the productivity and the resolution of the finished products might compromise the mechanical properties of these prints. For instance, Mana et al. [32] remarked that the rapidity in SLA prototyping could lead to inconsistencies in material characteristics, calling for more rigorous testing of materials and products used in this process. Husna et al. [33] also raised concerns about the environmental impact of photopolymers used in SLA, stressing the need for sustainable alternatives. Overall, while the latest findings present a leap toward more efficient SLA printing, there is a critical need to balance innovation with material integrity and sustainability.

Figure 2. Principle of Stereolithography (SLA) [27].

Figure 2. Principle of Stereolithography (SLA) [27].

SLS plotted in Figure 3 uses a high-power laser source to fuse material in powder layer per layer to form solid bodies in the middle of the powder bed. This technique is more suited for functional prototypes, in low-rate production, and for complex geometries in automotive, aerospace, and healthcare sectors. In SLS, there is no need for support structures due to powder use, which give the possibility to process more complex designs. However, drawbacks related to high energy consumption and the need for costly equipment require more focus in future investigations. The mechanical properties and durability of prototypes made by SLS vary in function of type and characteristics of powdered materials used.

Recent findings in SLS 3D printing have pushed the limits of material science, process optimization, and its applications. Several studies have emphasized innovations in polymer sintering processes, highlighting the role of advanced optics to improve layer resolution [34]. Other research explored the integration of artificial intelligence in process monitoring and the detection of defects [35]. The focus on sustainable practices is remarkable like other techniques of 3D printing, with research advocating for the use of bio-based materials and recycling of powder waste [36]. With the innovations in composite materials and their printability, SLS 3D printing reached unprecedented design flexibility and expanded functional capabilities [37]. Latest research revealed several challenges related to mechanical characteristics and thermal management of finished products [38,39,40], which need ongoing material characterization efforts. Overall, the landscape of SLS technology continues to evolve, driven by interdisciplinary collaboration and innovative research.

Figure 3. Principle of Selective Laser Sintering (SLS) [41].

Figure 3. Principle of Selective Laser Sintering (SLS) [41].

DLP uses a digital light projector to flash an entire layer of resin at once, curing it rapidly to produce layered 3D objects. Like SLA, DLP is used for quick prototyping, some medical applications like dentistry, and jewelry. The process is more flexible and rapid compared to other techniques of 3D printing due to layer curing and high-detail replication. However, it has similar issues with resin materials as SLA, including high costs and post-processing needs. Additionally, the process can also be limited by the size of the build platform. Recently Lin et al. [42], discussed the need of using eco-friendly materials in the DLP process to reduce the ecological footprint of traditional resins. In fact, they proposed an eco-friendly concept to solve the shrinkage issue in the DLP process. Critics found that the literature raised a key challenge regarding the post-processing needed by the DLP technique to achieve high precision in printed products, particularly the post-processing needed in effective resin removal, or to coat the print with the aim to improve its surface characteristics, flexural proprieties, and decrease its cytotoxicity, as highlighted by Dai et al. [43]. Wang et al. [44] noted that there are safety concerns about resin handling and toxicity, which emphasize the need for improved safety protocols in commercial applications. Meanwhile, Jiang et al. [45] highlighted the arising of layer adhesion issues during the printing process, which affect the quality and reliability of products made by DLP 3D printing. Overall, while this technology is evolving rapidly with promising materials and processes, further innovations and stringent safety regulations are crucial for its broader acceptance in commercial markets. Figure 4 plots the principle of this technique.

DLP, like SLA, is known for its precision and speed, but it faces significant challenges related to the toxicity of monomers and brittleness of finished prints. The uncured resin monomers used in these processes can be cytotoxic, posing risks to cells and tissues, which is a critical concern for biomedical applications. In fact, uncured resin monomers in DLP and SLA printing can lead to cytotoxic effects, impacting cell viability and proliferation. Studies have shown that post-print processing, such as washing with isopropanol and UV curing, can significantly reduce cytotoxicity, maintaining high cell viability in treated samples [46]. Emissions from 3D printers, including ultrafine particles, have been found to be toxic, with PLA and ABS materials showing adverse effects in cellular assays and in vivo models. Specific photopolymers, like E-Shell 300, have demonstrated severe developmental toxicity in biological models, although post-processing treatments can mitigate these effects [47]. Additionally, the brittleness of the printed parts can limit their functionality and durability. These issues need careful consideration and innovative solutions to enhance the safety and utility of DLP and SLA printed products. The brittleness of SLA and DLP printed parts is a noted limitation, affecting their mechanical properties and potential applications. However, certain post-processing methods, such as double IPA washing, can help maintain material integrity without inducing brittleness [46].

While the toxicity and brittleness of DLP and SLA printed parts present challenges, advancements in post-processing techniques and material coatings offer promising solutions. For instance, coating SLA printed parts with parylene C has been shown to effectively block toxicity, providing a safer alternative for biomedical applications [48]. These developments highlight the potential for safer and more durable 3D-printed products, expanding their applicability in various fields.

Figure 4. Principle of Digital Light Processing (DLP) [49].

Figure 4. Principle of Digital Light Processing (DLP) [49].

Selective Laser Melting (SLM), also known as Direct Metal Laser Sintering (DMLS) (see Figure 5), relies on the projection or modulation of a light pattern to selectively harden, sinter, or melt the material as a sequence of thin layers is deposited, allowing precise control of geometry, microstructure, and properties. The 3D printer used for this technique prints metal parts layer by layer by selectively melting metal powder using a high-power laser source, based on a 3D CAD model. A bed of fine metal powder is spread evenly, and the laser scans the surface to completely melt the designated area, forming solid cross-sections that fuse with the lower layers. Once each layer is complete, the build platform lowers, a new layer of powder is applied, and the process repeats until the part is complete [50]. SLM enables complex geometries, high strength-to-weight ratios, and near-full density parts. However, the process parameters need careful adjustments (such as laser power, layer thickness, and scan strategy) and post-processing (surface finishing, isotropic heat treatment, and sometimes remove unused supports) to achieve the desired mechanical properties and surface finish quality [51]. The SLM technique allows complete fusion of powders so that single-component metals, such as aluminum, can be used to create lightweight and strong spare parts and prototypes. The DMLS process agglomerates powders; it is limited to alloys, including those composed of titanium. These methods require additional work to compensate for high residual stress and limit the occurrence of distortion. They are used in the jewelry and dentistry sectors, as well as for spare parts and prototypes [52].

SLM/DLMS technologies have been successfully tested in aerospace, automotive sectors, and biomedical implants to produce components with complex geometries and tailored properties [53,54]. During these tests, many researchers highlighted the critical role of powder morphology, chemical composition, and particle size distribution in influencing oxidation, flowability, and final surface quality that meets the requirement of each field [55]. Extensive investigations focused on how laser power, energy density, scan speed, and strategies influence the mechanical properties, densification, and microstructure of SLM/DLMS parts. It is confirmed that the optimization of these parameters reduces defects such as porosity and residual stress, improves hardness, strength, and fatigue resistance across materials like AlSi10Mg, CoCrFeMnNi, Ti6Al4V, and 316L stainless steel [56,57,58,59].

Figure 5. Principle of Selective Laser Melting (SLM/DLMS) [41].

Figure 5. Principle of Selective Laser Melting (SLM/DLMS) [41].

Despite the advances remarked in this process, challenges persist in optimizing process parameters, ensuring part quality, and expanding material compatibility. Current research identifies gaps in controlling defects such as porosity, residual stress, and anisotropic mechanical properties, which limits the reliability and scalability of SLM/DLMS parts [60]. Controversies exist regarding the best strategies for process parameter optimization, with some studies emphasizing laser power and scanning speed effects [56,58], while others advocate for integrated control systems and hybrid manufacturing approaches [52]. The consequences of these unresolved issues include compromised mechanical integrity and restricted industrial adoption, underscoring the need for comprehensive understanding and innovation. Several studies highlighted non-linear relationships between energy density and mechanical outcomes, emphasizing the need for optimized parameter windows to avoid defects like keyhole formation or lack of fusion [58,61].

In Binder Jetting, a 3D printing technique, an adhesive binding agent is deposited onto thin layers of powdered material (ceramic-based or metal), to create a 3D object. During this technique, when the printer’s head moves over the build plate, it deposits binder droplets until the layer is complete; then, the powder bed moves downwards. Unlike conventional 3D printing techniques that typically melt or fuse materials, Binder Jetting produce complex geometries with various powders, including ceramics, metals, and polymers, making it notable for its versatility and speed. Binder Jetting is preferred in applications that need good aesthetics and form, such as packaging, architectural models, figurines, and toys. It is generally not suited for functional applications due to the brittle nature of the parts. To this end, several recent investigations have been focused on the optimization of the mechanical properties and quality of products made via Binder Jetting. Bianchi et al. [62] remarked a significant improvement in strength after tensile testing of Binder-Jetted stainless-steel components have undergone post-processing heat treatments. Zhao et al. [63] tested the use of new binder formulations using nano-zirconia dispersion as the jet solution to improve the quality and precision printed ceramics. In the work of Choi et al. [64] it is remarked that the use of composite binders could enhance the thermal resistance of prints. In fact, they remarked that the use of photocurable composite ink has remarkably improved the mechanical properties of ceramic filters produced through the Binder Jetting process. Moreover, the study of Heng et al. [65] identified that the incorporation of an inorganic metal salt binder in the Binder-Jetted tungsten heavy alloys remarkably improved the green density of this material compared to traditional organic binders. However, Janzen et al. [66] highlighted the curing strategy used in Binder Jetting has also an impact on performances of prints. Lastly, Tan et al. [67] underscored that binder jet 3D printing is a promising method for manufacturing sustained release solid dosage forms, offering a potentially efficient and scalable approach to pharmaceutical production. Figure 6 plots the principle of the Bender Jetting technique.

Figure 6. Principle of Binder Jetting process [68].

Figure 6. Principle of Binder Jetting process [68].

Analyzing the literature during the last few years, it is remarked that there is a notable improvement in printing speed, resolution, and material compatibility across SLA, SLS, DLP, and Binder Jetting 3D printing methods. For instance, innovations in image-shaped laser sintering have enhanced SLS efficiency by enabling a bigger sintering area, which overcomes traditional point-laser limitations [69]. DLP advancements include multi-material use and continuous liquid supply systems that improve throughput and mechanical properties [70]. SLA development is focused on high-precision photopolymer resins and rapid prototyping capabilities [71]. Binder jetting benefits from high manufacturing speed and low equipment costs, with emerging process parameter optimizations enhancing part quality [72]. The cost advantages of Binder Jetting are due to lower tooling and setup expenses, making it suitable for small to medium batch production [73]. It shows promise in tooling, medical instruments, and pharmaceutical solid products, with design freedom enabling complex geometries [74]. SLS offers competitive costs in producing complex polymer and pharmaceutical parts with reduced waste, it is favored in aerospace and automotive sectors for durable, lightweight parts [75]. However, SLA and DLP are noted for cost-effective prototyping and customization, especially in biomedical applications [76]. The two processes are better suited in producing high-resolution biomedical devices, dental implants, and customized scaffolds [77].

Many key technical limitations can be cited, such as limited mechanical strength and thermal resistance in SLA parts [71], powder flowability and material availability in SLS [78], and anisotropic shrinkage and porosity in Binder Jetting [79]. DLP faces challenges related to light diffraction, curing depth control, and resin formulation [80]. Post-processing complexity and regulatory compliance issues are recurrent themes, especially in biomedical applications [81]. SLA and DLP both have a limitation related to their scalability which is limited by building volume constraints, post-processing requirements, and material limitations, such as wear resistance and anisotropy related to layer orientation and light penetration control. Process parameter optimization and novel photocurable resin formulations, especially those incorporating smart and recyclable materials, extend their functional scope but still face challenges in industrial-scale deployment. SLS struggles with powder flowability, thermal stresses, and limited material diversity, which complicate post-processing and affect mechanical uniformity. These constraints impact cost-effectiveness and environmental sustainability, particularly in pharmaceutical production, where regulatory compliance and energy consumption pose additional hurdles.

Binder Jetting challenges, such as layer bonding, sintering shrinkage, defect control, and achieving high part density limit mechanical performance and accuracy. Advances in powder characteristics, bimodal particle distributions, and process parameter optimization have improved these aspects but requires further refinement to meet stringent industrial quality standards consistently.

Overall, while each 3D printing method exhibits promising technological advancements and niche applicability, significant efforts remain necessary to standardize efficiency metrics, develop scalable multi-material processes, and address post-processing complexities. Integration of AI and IoMT for process control and quality assurance emerges as a key trend with the potential to enhance reliability and repeatability. Future research should prioritize holistic evaluations encompassing life cycle assessments, regulatory frameworks, and cost–benefit analyses to accelerate industrial adoption and optimize additive manufacturing’s transformative impact across sectors.

Material Jetting plotted in Figure 7, involves the precise deposition of material droplets layer by layer to form printed products. This process typically uses photopolymers or other materials cured during the printing technique with UV light or thermal methods, which allows for the production of high-quality prints with variable material properties. Recently in Material Jetting researchers have developed new photopolymers when used with this technique could lead to printed products with better mechanical strength and flexibility, which makes the process suitable for functional applications in industries such as automotive and aerospace [82]. Additionally, new records of print speed and resolution have been reported, with innovated systems that achieve resolutions below 20 microns [83]. Furthermore, the integration of Multi-Material Jetting techniques has opened the ability to produce objects with varying thermal and mechanical proprieties within a single print [84]. Another noteworthy innovation is the improved biocompatibility of specific materials, paving the way for medical devices and tissue engineering applicability [85].

Figure 7. Principle of Material Jetting 3D printing.

Figure 7. Principle of Material Jetting 3D printing.

Material Jetting key advantages include high part resolution and surface finish, multi-material and full-color capabilities, and relatively fast build times for small to medium parts. Disadvantages encompass material cost, fragility of some resins, and sensitivity to environmental factors such as humidity and temperature, which can affect droplet consistency and cure. Technical limitations involve droplet size control, adhesion between layers, and the need for post-processing to achieve final mechanical properties [86]. limitations also include restricted material property ranges (often lower strength compared to some other AM technologies) and printer-specific constraints like jetting frequency and purge waste. Recent literature highlights ongoing improvements in multi-material compatibility, color accuracy, and printer reliability, while addressing challenges in long-term part performance, thermal effects on cured polymers, and process controllability at high throughput [87].

Direct Ink Writing (DIW) (plotted in Figure 8) stands as a pioneering additive manufacturing technique that has gained significant momentum in recent years due to its versatility and precision in material processing [88]. DIW allows for the precise deposition of various materials layer by layer, creating complex three-dimensional structures with tailored shapes, sizes, and functionalities. The technique has emerged as the most versatile 3D printing method for the broadest range of materials, which enables printing approximately any material if the precursor ink can be engineered to demonstrate appropriate rheological behavior [89].

Recent developments in hydrogel-based DIW have shown remarkable progress in biomedical applications. The technique enables precise deposition of hydrogel inks layer by layer, opening possibilities for applications spanning from tissue engineering to soft robotics and wearable devices. In fact, innovative ink formulations have been developed using the salting-out effect to create 3D printable hydrogel inks with broadly adjustable mechanical properties [90]. The optimization of alginate–gelatin hydrogel properties has been achieved through Principal Component Analysis and K-means clustering, revealing that viscosity, storage modulus (G′), and loss modulus (G″) govern printing behavior [91].

Multi-layered synthetic blood vessels that mimic biological blood vessel properties have been successfully printed, demonstrating practical applications in surgical training [90]. Conductive bio-based hydrogels for wearable electrodes have been developed, achieving 0.40 mm resolution via handheld 3D printers and showing 88% higher signal-to-noise ratio compared to standard Ag/AgCl electrodes [92].

In addition, DIW has proven particularly effective for ceramic processing, addressing traditional manufacturing limitations in producing complex geometries. Recent advances include the development of NbC-Ni matrix cermet using water-based feedstock inks containing 40 vol% cermet powder mixture and 25 wt% Pluronic F-127 hydrogel [93]. The technique has been successfully applied to create doped β-tricalcium phosphate bio-ceramics for bone repair applications, with co-doped compositions showing enhanced thermal stability, densification, and mechanical properties [94]. Significant enhancement of compressive strength values has been achieved in ceramic components compared to some of the literature data, with successful printing of macroporous scaffolds showing reduced microcracks and macropores [94]. The optimization of sintering treatments and ceramic ink compositions has enabled the design of new components for catalytic applications, with 3D-printed parts featuring rectilinear infill patterns and 40% infill density favoring catalytic performance [95].

DIW has also emerged as an appealing method for biomedical applications, particularly in developing functional 3D scaffolds with robust structural integrity for tissue and cell growth. The technique has been successfully applied to create biocompatible ceramic scaffolds that support cell culture applications, with MDCK cells showing uniform growth and proliferation, maintaining viability for up to 35 days [96].

Several technical limitations remain, including the complexity of ink formulation and printing processes, particularly for functional conductive hydrogels. The need for post-processing treatments such as sintering for ceramics adds complexity to the manufacturing workflow. Limited long-term stability data for bio-printed structures and the scalability of advanced formulations for commercial production remain concerns.

Figure 8. Principle of Direct Ink Writing (DIW) [97].

Figure 8. Principle of Direct Ink Writing (DIW) [97].

Additive Friction Stir Deposition (AFSD) (Figure 9 [98]) is a 3D printing method that progressively builds parts by feeding a consumable metal rod into a rotating, heated tool that traverses the build path, which causes plastic deformation, fracture, and interfacial bonding without melting the base material, and enabling a layer-by-layer deposition with inherently refined microstructure. AFSD applications span aerospace, automotive, biomedical implants, tooling, and complex lightweight structures, including high-strength aluminum and magnesium alloys, copper, and dissimilar material combinations.

Leveraging advantages include low residual porosity, reduced oxidation, minimal warped distortion, good surface integrity, near-net-shape capability, and the potential for in situ heat treatment and graded material properties. The process faces several disadvantages, like relatively slow build rates, equipment complexity, limited deposition height per pass, sensitivity to tool-path optimization, and challenges with post-build surface finish and dimensional accuracy.

Technical limitations include material compatibility with certain alloys, tribological wear of tools, thermal management, residual stress control, sensitivity of process parameters (rotation speed, feed rate, plunge depth), and the need for precise clamping and continuous monitoring to ensure defect-free joints.

Figure 9. AFSD process with different modes. (a) Rod with non-consumable tool. (b) Consumable tool. (c) Powder with non-consumable tool. (d) Powder with non-consumable tool [98].

Figure 9. AFSD process with different modes. (a) Rod with non-consumable tool. (b) Consumable tool. (c) Powder with non-consumable tool. (d) Powder with non-consumable tool [98].

Research on technological advancements in Additive Friction Stir Deposition (AFSD) has emerged as a critical area of inquiry due to its potential to overcome limitations inherent in fusion-based additive manufacturing processes, such as porosity, cracking, and residual stresses [99,100]. Since its inception, AFSD has evolved as a promising AM technique that uses frictional heat and plastic deformation to deposit materials without melting, which enables the fabrication of defect-free components with wrought-like mechanical properties [101]. The importance of AFSD is highlighted in its applicability across automotive, aerospace, and nuclear industries, where high deposition rates and superior material properties are essential [102]. Recent studies report that AFSD can achieve mechanical strengths comparable to or exceeding those of conventionally processed alloys, with deposition rates conducive to large-scale manufacturing [103].

Despite these advances, challenges remain in optimizing AFSD for new materials, enhancing process efficiency, and expanding innovative applications. The specific problem lies in the limited understanding of process–structure–property relationships across diverse alloys and composites, as well as the technological readiness for industrial adoption. Knowledge gaps persist regarding the control of microstructural uniformity, defect mitigation such as kissing bonds and tunnel defects, and the influence of process parameters on mechanical performance [104,105]. Competing perspectives debate the trade-offs between deposition speed and mechanical integrity, with some studies emphasizing high rotational speeds for grain refinement, while others highlight the adverse effects of thermal cycles on ductility [106]. The consequences of these gaps include restricted scalability and inconsistent part quality, impeding broader industrial implementation [107].

Hybrid Additive Manufacturing (Hybrid-AM) is a trend in 3D printing that combines additive manufacturing techniques such as directed energy deposition or powder bed fusion with a secondary manufacturing process, which could be a traditional subtractive method like milling, grinding, rolling, drilling, and turning, or a secondary process that uses heat, as is typically the case in various welding techniques. The novelty in this process comes from the machine tool, which has a custom head capable of performing a dual task. It can remove or add material to a part without needing to move it to a new station. The approach enables the manufacture of near-net shapes followed by precise finishing, which reduces post-processing time and enables multifunctional components with integrated tooling channels, cooling passages, or embedded sensors. The technology can leverage the material efficiency of additive processes while taking advantage of the precision and dimensional accuracy of conventional machining, such as sampling, improving feature resolution, surface quality, and the ability to work with a wider range of materials, including composites and difficult-to-machine metal alloys.

The secondary process in hybrid AM is generally used to eliminate common defects encountered in conventional 3D printing such as keyholes, cracks, residual stresses, pores, etc. Each secondary process is tailored to a specific application, which must be selected based on these requirements. Secondary processes can be based on cold working, such as burnishing, rolling, shot penning, and machining. It can also use or generate heat, as in friction stir welding, laser-assisted hybrid AM, electron beam welding, and pulsed laser deposition [108]. Figure 10 and Figure 11 show the principle of some AM hybrid techniques with different secondary processes.

Key findings during the last few years indicate that hybrid AM systems can reduce production time by up to 50% and improve surface roughness by 70%, while maintaining dimensional accuracy within ±0.5 µm [109]. The integration of post-processing technologies, such as machining, into additive manufacturing processes is seen as a viable solution to meet the rigorous requirements of industries such as aerospace and biomedicine [110]. Actually, while analyzing different hybrid AM techniques, Hamran et al. [111] remarked that Wire Arc Additive Manufacturing (WAAM) is able to improve part precision, surface quality, geometry control, efficiency, and environmental impact. Laser Metal Deposition (LMD) integration improves feature addition, precision, stability, and resource efficiency. The use of machining with SLM intricates part feasibility, enhances surface quality and mechanical properties. However, their combination with Fused Filament Fabrication (FFF) addresses the surface finish and geometric precision as well as anisotropy. Laser-assisted methods like LOMM and LAM improve material removal, efficiency and surface quality. Vibration-assisted techniques boost material removal rate, surface quality, and overall machining performance.

Conversely, while hybrid additive manufacturing presents numerous benefits, some experts argue that the complexity of integrating multiple technologies may hinder widespread adoption, particularly for smaller manufacturers lacking the necessary resources and expertise. In fact, technical limitations in hybrid AM processes include higher equipment and maintenance costs, longer cycle times for hybrid workflows, thermal management concerns, and process compatibility between deposition and removal steps. Material–property homogenization, residual stresses, and anisotropy must be carefully managed, and process optimization often requires multidisciplinary modeling and robust process-monitoring strategies [112]. Overall, hybrid additive manufacturing holds promise for aerospace, biomedical, and tooling applications by enabling functionally graded materials, complex interior channels, and rapid prototyping with scalable production potential [113].

Table 1. Comparison between AM technologies.

Technology	Principle	Advantages	Limitations	Key Challenges in the Future
FDM	Melts and extrudes thermoplastic filament layer by layer	Wide range of materials; Effective cost; User-friendly; Accessible	Lower productivity, especially for complex designs; Limited resolution; Material warping	Test several composite materials based on thermoplastics; Improve print speed and surface quality; Develop printers for high scale products
SLA	Cures liquid photopolymer resin using UV light layer by layer	High precision and detail; Good surface finish; Wide range of materials	Higher post-processing time; High resin cost; Limited build size	Enhance the material choice and sustainability; Reduce post-processing times; Test applications in bigger scales
SLS	Uses a laser to selectively fuse powdered materials layer by layer	Strong and functional parts; Complex geometries; Without the need of supporting structures	High equipment cost; Limited material options; Low surface finish; Low resolution	Test wider range of materials and integrate composites; Reduce costs and improve scalability; Optimize the surface finish and precision of printed products
DLP	Uses a digital light projector to cure resin layer by layer	High quality of prints; Fast printing speeds; Good for prototyping	Small range of materials; Requires post-processing; Resin can be hazardous	Develop safer materials; Innovate eco-friendly or bio-based resins; Test composite resins; Test wider range of printing materials
SLM/DLMS	Relies on the projection or modulation of a light pattern to selectively harden, sinter, or melt the material as a sequence of thin layers is deposited	Enables complex geometries; High strength-to-weight ratios; Allows complete fusion of powders to create strong parts	Challenges in optimizing process parameters; Ensuring part quality, and expanding material compatibility; Gaps in controlling defects such as porosity, residual stresses, and anisotropic mechanical properties, which limits the reliability and scalability of SLM/DLMS parts	Require additional work to compensate for high residual stress and limit the occurrence of distortion; Several studies highlighted non-linear relationships between energy density and mechanical outcomes, emphasizing the need for optimized parameter windows to avoid defects like keyhole formation or lack of fusion
Binder Jetting	Deposits a liquid binder onto layers of powder to form 3D objects	Fast printing speeds; Suitable for large parts; Minimal waste generation	Limited mechanical properties; Requires post-processing (e.g., sintering); Low surface finish	Expand material options; Improve part strength and durability; Optimization to improve the surface finish
Material Jetting	Sprays droplets of liquid material which are cured layer by layer	Multi-material capabilities; High resolution and surface quality	Requires extensive post-processing depending on designs; High material costs	Improve compatibility and range of substances; Develop more affordable materials
DIW	Uses a viscous, shear-thinning ink with a yield stress, pushed through a nozzle by pneumatic, screw, or piston-driven pressure to deposit continuous strands layer by layer	Technique emerged as the most versatile 3D printing method for the broadest range of materials; Creating complex three-dimensional structures with tailored shapes, sizes, and functionalities	Complexity of ink formulation and printing processes, particularly for functional conductive hydrogels; The need for post-processing treatments such as sintering for ceramics; Limited long-term stability data for bio-printed structures; Scalability of advanced formulations for commercial production	Ink rheology design and predictability; controlling micro- to macro-scale architecture within a single print to realize graded porosity, aligned fiber networks, or multi-material interfaces; Achieving high-resolution features without sacrificing build speed or causing nozzle clogging; developing low-temperature, energy-efficient, and scalable post-processing routes compatible with heat-sensitive components and biological materials; Designing green, bio-based, or recyclable inks with comparable performance; Reducing hazardous solvents and improving long-term stability
AFSD	Feeding a consumable metal rod into a rotating, heated tool that traverses the build path, which causes plastic deformation, fracture, and interfacial bonding without melting the base material, and enabling layer-by-layer deposition	Low residual porosity; Reduced oxidation; Minimal warped distortion; Good surface integrity; Near-net-shape capability; Potential for in situ heat treatment and graded material properties	Relatively slow build rates; Equipment complexity; Limited deposition height per pass; Sensitivity to tool-path optimization; Challenges with post-build surface finish and dimensional accuracy	Optimizing AFSD for new materials; enhancing process efficiency; Expanding innovative applications; Enhance understanding of process-structure–property relationships across diverse alloys and composites, as well as the technological readiness for industrial adoption.
Hybrid AM	Combines additive manufacturing techniques such as directed energy deposition, or powder bed fusion with a secondary manufacturing process such as machining or welding	Enables the manufacture of near-net shapes followed by precise finishing; Reducing post-processing time; Could leverage the material efficiency of additive processes while taking advantage of the precision and dimensional accuracy of conventional processes; Improving feature resolution, surface quality, and the ability to work with a wider range of materials	Higher equipment and maintenance costs; Longer cycle times for hybrid workflows; Thermal management concerns; Process compatibility between deposition and removal steps; Material-property homogenization; Residual stresses; Anisotropy must be carefully managed; Process optimization often requires multidisciplinary modeling and robust process-monitoring strategies	Harmonizing disparate processes into a single consistent workflow; Real-time process monitoring and closed-loop control across modalities to ensure dimensional accuracy, surface finish, and thermal stability; Designing compatible material pairs with strong, durable interfaces; Managing thermal histories and diffusion across interfaces to avoid cracking, residual stresses, or delamination; Controlling heat input from different processes to minimize warpage, distortion, or phase changes

and

Table 2. AM technologies key findings during the last two years.

Technology	Main Findings	Process Parameters Range	Critics	References
FDM	In FDM process it is widely important to fine-tun the temperature, print speed, and layer height to achieve better print quality and performance particularly when using materials like PLA.	Build speed PLA/ABS/PET-G FDM: often in the range of ~20–80 mm/s. Metal-filled filaments or specialized materials: may require lower speeds, ~5–40 mm/s. Nozzle temperature (°C) - PLA: ~190–230 - ABS: ~210–250 - PET-G: ~220–250 Bed or chamber temperature (°C) - PLA/ABS: bed ~40–110 (depends on material) - PET-G: ~60–100 Tensile strength of printed parts - PLA: ~50–70 MPa - ABS: ~40–60 MPa - PET-G: ~40–60 MPa Surface roughness (Ra) - FDM: generally, ~6–20 μm for well-tuned prints; higher with coarse layer heights.	The heavy focus on sustainability without equally analyzing the mechanical performances of bio-based materials in functional applications. Most investigations have focused on particular materials (mainly PLA) and particular printer setups, which may limit the applicability of their findings to other materials and printers.	[16,17,18,19,20,21,22,23,24,25,26,27]
SLA	Faster cure time is recorded using enhanced UV resins, better print precision and detailing. Recent studies highlighted remarkable improvements in photopolymer resin optimization, using procedures such as neural network approaches to enhance mechanical properties and bio-compatibility certifications. Which enabled the safer and more effective use of SLA-made products in healthcare applications.	Build speed Photopolymers: commonly 5–100 mm/s, with many studies clustering around 20–60 mm/s for balanced cure and build time. Layer height (µm to mm) SLA/Epoxy resins: 25–200 µm (0.025–0.2 mm), with common choices around 50–100 µm for good surface finish and dimensional accuracy. Nozzle/laser temperature Most photopolymer SLA/DLP uses a photoinitiation process rather than a heated nozzle; some dual-curing systems may involve modest temperatures during post-curing (room temp to ~60–80 °C for post-curing, depending on resin). Tensile strength (MPa) SLA epoxy resins: roughly 40–120 MPa depending on resin chemistry, curing, and orientation; biocompatible dental resins may be in the lower to mid-range (20–60 MPa) but can reach higher with optimized cure. Surface roughness (Ra, µm) Post-processing and layer height dominate: typical as-printed Ra ~1–5 µm for fine layers with smooth finishes; with larger layer heights, Ra can rise to ~10–25 µm or more.	While research identified challenges in post-processing, it may not give alternatives or innovative strategies to overcome these challenges. The critical dependence between SLA performances and the photopolymer resins proprieties. Many photopolymers suffer from issues such as lack of long-term stability, brittleness, and limited temperature resistance. Which can influence mechanical performance, durability, and sustainability of prints.	[28,29,30,31,32,33]
SLS	The last advances in this technique have marked a remarkable enhancement of the mechanical performance and applicability of polymer-based materials, especially in manufacturing composites and innovative oral dosage forms. Several investigations have demonstrated advancement in material formulations, such as the exploitation of the use of copovidone and paracetamol in SLS for pharmaceutical products and using amino-silane treatments to improve the mechanical properties of PA12-based composites.	Build speed (mm/s) Commonly 0.5–5 mm/s (depending on machine and part size). Laser energy density Typical ranges: 0.5–3.0 J/mm2 (depends on material, scan speed, layer thickness). Part bed temperature (°C) PA12 and similar powders: bed temperatures around 160–190 °C. Higher for tougher polymers. Tensile strength (MPa) PA12 parts: typically 30–50 MPa. Filled or reinforced polymers: higher, can approach 60–100 MPa in optimized cases. Surface roughness (Ra, μm) As-built SLS PA12: Ra often in the 5–15 μm range; with polishing or post-processing can be below 5 μm.	The need for precise experimental parameter identification and thermal modeling could complicate the SLS process, which leads to a challenge in achieving consistent accuracy of printed parts. In addition, dependence on high-quality powders and the risk of defects related to particle size distribution can limit the efficiency and scalability of SLS manufacturing.	[34,35,36,37,38,39,40,41]
DLP	Achievement of higher printing speeds which enables more efficient production in high-detailed applications. Expanded applications in dental technologies. Novel strategies have been presented for better efficiency in DLP systems.	Build speed (mm/s) photopolymers: commonly 5–50 mm/s. Tensile strength (MPa) typically 20–100 MPa, depending on resin (epoxies often higher; some dental/bio resins lower). Surface roughness (Ra, µm) As-printed: 1–20 µm depending on layer height, resin, and post-processing; post-processing can reduce Ra to below 1 µm in optimized cases.	Optimizing the printing speed and resolution need to focus on addressing how these modifications affect the mechanical performance and long-term durability of prints.	[42,43,44,45,46,47,48,49]
SLM/DLMS	Laser power, scan speed, hatch spacing, layer thickness, and scanning strategy critically influence density, porosity, residual stresses, microstructure, and mechanical performance. Non-uniform cooling and thermal gradients in SLM/DLMS lead to residual stresses that cause warping, cracking, and dimensional inaccuracies. Hot isostatic pressing (HIP), heat treatments, surface finishing, and machining are usually required to reach recommended density, strength, and fatigue performance.	Build/recoat speed (mm/s) and scan strategy Typical laser scan speeds for metals: roughly 0.5–5 mm/s. Laser energy density (J/mm2) Energy density often tuned around 60–180 J/mm2. Powder bed temperature or preheating Preheating for certain alloys (e.g., Ti, Al alloys) can be 100–600 °C depending on material and system. Surface roughness (Ra, µm) As-built SLM surfaces: Ra ~5–15 µm on key features; post-processing can reduce to sub-5 µm.	Conclusions about mechanical properties usually assume post-processing steps (HIP, heat treatment) that may not be available in all production settings, affecting real-world applicability. Many studies focus on technical feasibility without robust assessment of cycle time, cost, and scalability to production volumes. Fatigue, corrosion, and biocompatibility data are often limited to short-term tests, leaving uncertainties about long-term reliability. Many papers rely on simulations or energy density heuristics that do not fully account for complex thermal history, microstructure evolution, or residual stresses, leading to overconfident predictions.	[50,51,52,53,54,55,56,57,58,59,60,61]
Binder Jetting	The highlight of material versatility including applications in ceramics and metals. Highlight of new technologies to improve the mechanical properties of prints such as nanoparticle dispersion infiltration or post-heat treatments. Optimization of the process parameters for enhanced part density.	Print speed (mm/s) Typical practical speeds for fine features or dense parts: ~5–25 mm/s. High-throughput, coarse-feature builds: can approach 60–100 mm/s. Tensile strength Metals in binder-jetted parts can range from ~200–900 MPa after sintering. Surface finish and roughness Typically 5–20 µm on functional faces.	Insufficient analysis of limitations, such as challenges related to part strength, surface finish, and cost of materials and processing. Further exploration of long-term performance, scalability, and applicability across different industries.	[62,63,64,65,66,67,68]
Material Jetting	Careful optimization of pre-processing steps can lead to promising accuracy of prints. The composition and distribution of materials at the voxel-scale promisingly affect the structure–performance relationships, potentially improving the design flexibility of prints. Integrating a topology optimization and numerical analysis to predict experimental outcomes, can improve the intended results in Multi-Material Jetting.	Print speed (mm/s) Layer by layer: ~10 to 60 mm/s Typical practical speeds for fine features: 5 to 30 mm/s. Ultra-fine feature printing or very viscous inks, speeds often limited to 5–15 mm/s to maintain jetting stability and gap control. Surface roughness (Ra, µm) Commonly 1–10 µm for well-controlled resins and small features; rougher surfaces up to ~20–25 µm for larger features or higher viscosity resins. Dimensional accuracy Tolerances often in the range of ±0.1–0.3% for small to medium parts. Tensile strength (MPa) Roughly 20–80 MPa depending on resin chemistry and interfacial design; with favorable post-processing, higher values are possible.	The focus on pre-processing might not be sufficient to assess the impact of material properties on dimensional precision. It is needed to explore the practical implications of varying voxel compositions in terms of cost-effectiveness and manufacturing feasibility. Studies should consider long-term stability and degradation behavior of bio-compatible materials.	[82,83,84,85,86,87]
DIW	DIW is capable of processing a wide variety of scales and materials (hydrogels, ceramic-based composites, metals, and bio-based materials), offering geometric customization and adjustable mechanical properties. Control of ink formulation (viscosity, thixotropy, colloidal stability, rheology) and printing parameters (pressure, extrusion speed, temperature) is crucial for geometry, resolution, and precision. Hydrogels and bio-hybrids: tunable mechanical properties (rigidity, elasticity) can be obtained through combinations of alginate-gelatin, salting-out, and other matrix strategies. These properties are essential for biomedical applications.	Print speed (mm/s) Commonly 5–50 mm/s, with slower speeds for high-viscosity inks to ensure continuous extrusion. Surface roughness (Ra) Hydrogels and soft inks: ~1 to 10 µm for well-controlled filaments and fine features; roughness can be higher (10–50 µm) for coarse strands or larger features. Ceramic/particle-filled inks: ~5 to 20 µm for fine networks; 20–50 µm for more open or porous structures. Composite inks with pigments/fillers: ~5 to 30 µm depending on particle size and printing conditions. Tensile strength Hydrogels and soft polymer inks: roughly 0.1 to 10 MPa. Higher-strength variants with specialized chemistries and crosslinking can reach ~10–20 MPa. Semi-rigid polymer inks typically 10–70 MPa. With optimization (filler incorporation, crosslink density): 50–100 MPa is possible.	Correlation between ink composition and mechanical response: need to understand how each component and each printing condition influences viscoelastic behavior and long-term stability. Possible variability in ink preparation and printing parameters affecting the consistency of properties. Comprehensively characterize viscoelasticity and stability under relevant biological conditions. Optimize the salting-out process and alginate/gelatin ratios to achieve a targeted range of elastic modulus and other mechanical proprieties.	[88,89,90,91,92,93,94,95,96,97]
AFSD	The precise control of the thermal regime (heat input, rotation speed, feed rate) and the number of deposition passes is essential to achieve a homogeneous microstructure and consistent mechanical properties. The microstructure of AFSD parts is highly dependent on the number of passes, the tool profile, the feed rate, and the thermal parameters. The tool profile (pointed, cylindrical, multi-pin) and operating temperature control strongly influence microstructural integrity and the formation of internal residues.	Print speed (mm/s). small parts, high detail, build speed: roughly 5–20 mm/s, with slower speeds to maintain layer uniformity and proper fusion. Moderate-speed ~20–60 mm/s for balanced quality of prints. High-throughput AFSD builds (large parts, lower detail): ~60–150 mm/s or higher. Deposition/fusion energy Rough ranges: 0.5–5 J/cm2. Tensile strength ranging from 87.8 to 320 MPa.	The final microstructure is highly sensitive to deposition parameters: rotational speed, heat input, tool geometry (pin/profiles), number of passes, feed rate, and in some studies, closed-loop temperature control. Increasing the number of passes and optimizing heat input often improves hardness and strength but can induce residual stresses if not properly managed. Defects can arise if parameters are not optimized: improper tool profiles, heat input, and insufficient passes can still cause internal residues, microcracking, or non-uniform grain structure.	[98,99,100,101,102,103,104,105,106,107]
Hybrid AM	New innovations in hybrid AM techniques such as laser-arc methods, which lead to promising properties, microstructures, and performance of several composites and metallic materials. Importance of refining processing parameters to achieve better geometrical accuracy of prints. Many studies have focused on the optimization of mechanical proprieties (ductility, tensile strength) using controlled microstructural evolution. Applicability of hybrid AM techniques could cover many fields from aerospace materials to bio-inspired designs, suggesting its versatility and potential for future innovations.	Printing speed Ranging from extremely slow for fine details (e.g., 0.1 to 8 mm/s in a polymer extrusion example) to faster speeds on the order of dozens to hundreds of millimeters per second for metal deposition. Surface roughness For polymer hybrid manufacturing, values are as low as Ra = 1.94 μm. Hybrid processes show significant surface quality improvements of approximately 70% compared to conventional AM processes. Dimensional accuracy Hybrid systems report within ±0.5 μm. Material utilization rates exceed 95%. Tensile strength From below 100 MPa for some polymer composites to over 1000 MPa.	The need to test the durability and environmental use of materials produced by hybrid AM. There are key challenges to achieve a balance between different competing factors (e.g., depositional rates, thermal effects) which affect material performance, and lead to inconsistencies during processing. Issues related to the variability in material feedstock and the quality control. Many experimental setups are not easily scalable for industrial production. Hybrid AM could be costly due to sophisticated equipment and materials, which may not be economically viable for all applications, particularly for industries with tight margins.	[108,109,110,111,112,113,114,115,116,117,118,119,120,121,122]

draw, respectively, a comparison between the different additive manufacturing techniques, as well as the main findings during the past few years. Table 2 describes the range of some process parameters noted from the cited references at the aim to make a comparison between the different AM techniques.

2.2. Materials Used Within AM Technologies

Additive manufacturing (AM) technologies use a variety of materials (described in

Table 3. Properties of AM materials.

Material	Description	Properties	Applications	AM Technique
Metals	Titanium, aluminum, stainless steel,	High strength, high toughness High durability	Automotive, aerospace, healthcare	Electron Beam Melting (EBM), Selective Laser Melting (SLM).
Polymers	PLA, ABS, PETG, Nylon, TPU, PVA	Low cost, easy to print, availability	Consumer products, prototyping	FDM, SLS, SLA
Ceramics	Alumina, Zirconia	High hardness, high toughness	Aerospace, healthcare	Binder Jetting, Precision Ceramics
Composites	Glass fiber, carbon fiber,	High stiffness high strength,	Automotive, Aerospace, sports equipment	FDM, CFF (Continuous Filament Fabrication)

), each of these materials is selected for specific applications and properties. Common materials include thermoplastics like PLA (polylactic acid) and ABS (Acrylonitrile Butadiene Styrene), which are extremely used in FDM technique due to their low cost, ease of printing and availability. Powder bed fusion techniques like SLM and EBM usually uses metal powders such as titanium, aluminum, and stainless steel. These metals provide high strength, toughness and durability for aerospace, automotive and some medical applications. Additionally, ceramics (Zirconia and Alumina usually used within Binder Jetting or Precision ceramics) and composites (usually used in FDM and CFF techniques) starting to be used in 3D printing due their unique properties, catering to applications that require high hardness, high heat resistance, and high toughness along with a lightweight

Recently, several investigations have underscored a significant trend toward innovation of material compositions tailored to meet specific AM application requirements. Among the notable breakthroughs are advanced ceramics and high-strength thermoplastics that demonstrated an improved printing abilities and performances while decreasing waste [123,124]. Additionally, the presentation of multi-material systems such as polymer-derived ceramics has made it possible to exploit new functionalities and complex design features in a single printout [125]. In the realm of metal additive manufacturing, new innovations in metal alloys helped in the manufacturing of products with better mechanical characteristics and thermal resistance, especially for demanding industries such as automotive and aerospace [126,127] as presented in Figure 12. As stated by Bernalteet al. [128]; Saraswat et al. [129], the exploration of eco-friendly materials, including recyclable and bio-based options, have addressed the growing emphasis on sustainability and the environmental challenges associated with AM techniques. Saran et al. [130] highlighted the advantage of integrating several composite materials in 3D printing technologies and their role in advancing the process towards functional applicability. While Dede et al. [131] focused on advancement in SLA resins that enhanced print`s strength and resolution. Patel and Minko [132] explored tailored polymer blends for improved mechanical performance, and Ahmad et al. [133] investigated bio-compatible materials for medical use, in the advancement of healthcare technology. Ukwaththa et al. [134] stated that with the use of AI and ML algorithms one can determine the best mixing ratios, additives, and curing agents to reach the best material proprieties such as elasticity, strength, and durability. Optimization using these tools could explore new material combinations for better prints performance, lowers production costs, and decreased material waste. Yu et al. [135] focused on the evaluation of the various process parameters likely to affect multi-material printing. They highlighted the complex balance needed between material properties and printing techniques, which could be enriched by incorporating empirical data from real applications. Park et al. [136] bring interest to the design of new polymers, reiterating innovation in polymer chemistry to meet requirements of AM techniques, yet potentially underestimating the market readiness of these materials. Clemens et al. [137] analyzed advanced ceramics, illustrating the technical challenges in their printability, highlighting the need for interdisciplinary approaches to address these challenges. Ahmad et al. [138] investigated the use of smart materials, such as Shape Memory Materials (SMM) with integrated functionalities. The use of smart materials as innovation in 3D printing could announce major modifications in the product design and manufacturing process from static structures to dynamic structures which can revolutionize AM but also hint at the ongoing challenges related to scalability and cost-effectiveness. Finally, As the future of an environmentally friendly AM process, Piepoli et al. [139] underscored the crucial challenge of recycling AM materials, emphasizing the dual difficulties of sustainability and resources recovery. The development of biocompatible materials suited for healthcare products is also a key challenge in AM as highlighted in the paper of Mobarak et al. [140]. In fact, it is extremely important to check medical issues during the selection of printable materials. These materials should not only meet the mechanical and structural requirements for various medical devices and implants but also ensure compatibility with biological tissues. Investigations carried out on AM materials have demonstrated the quick development of these processes as well as the ongoing challenges related to material optimization, process efficiency and sustainability. With advanced research the range of AM materials becomes wider as plotted in Figure 13.

Table 4. New materials tested in AM technologies.

Material	AM Technique	Main Findings	References
Graphene-reinforced Thermoplastic	FDM	Enhancement of the tensile strength and thermal conductivity up to 30%.	Raja et al. [143] Liesenfeld et al. [144] Maleki et al. [145]
PLA/PBAT/PHBV Bio-based Resin	FDM	Better biodegradability with maintained structural integrity.	Apicella et al. [146] Ali et al. [147]
AlSi10Mg aluminum Alloy	Selective Laser Melting (SLM)	Remarkable improvement in ductility and fatigue resistance.	Li et al. [148] Pawlowski et al. [149] Ramesh et al. [150]
Continuous Carbon Fiber/Epoxy Composite	Continuous Filament Fabrication (CFF) Material Extrusion	Higher impact resistance, needed for aerospace components.	Deng et al. [151] Maqsood et al. [152]
Short Carbon Fiber-Reinforced Polylactic Acid SCFR-PLA	Fused Filament Fabrication (FFF)	Promising potential of SCFR-PLA composites in small-scale wind energy systems. Which could be projected to other applications. There is an important role of fiber alignment in stress transfer, fracture mechanisms, and anisotropic failure modes.	Ben Said et al. [153] Baharlou and Ma [154] Bouhamed et al. [155] Ammar et al. [156]
Zirconia (ZrO2) Ceramic	Binder Jetting, DLP, SLA, LCM (Lithography-based Ceramics)	High accuracy is achieved with reduced thermal degradation during sintering. Zirconia exhibits promising potential in dental applications due to its enhanced mechanical characteristics, biocompatibility, and aesthetic qualities.	Su et al. [157] Yoo et al. [158] Guan et al. [159]
NiTi Shape Memory Alloy	Direct Energy Deposition (DED)	Improved shape recovery capabilities and higher fatigue life.	Dzogbewu and de Beer [160] Cohen et al. [161]
Aluminum/TiC-graphene hybrid nanocomposite.	Additive Friction Stir Deposition (AFSD)	Enhancements in material properties include approximately 42% increase in hardness, 66% reduction in wear rate, 15% decrease in friction coefficient, and 33% reduction in corrosion rate.	Sahraei, and Mirsalehi [162]
Hybrid Aluminum/TiN-Diamond or MoS2-diamond hybrid nanocomposite	Additive Friction Stir Deposition (AFSD)	Adding TiN/ND or MoS2/D nanoparticles to the aluminum alloy soft base improved the mechanical, metallurgical, and electrochemical properties of the produced parts.	Abbasi-Nahr et al. [163,164]
Gpt/Al2O3/PLA composite	FDM	An advanced electrochemical platform featuring cost-effective, 3D-printed electrodes designed for the detection of sulfamethoxazole (SMZ) in honey samples, providing improved sensitivity and affordability for regulatory and safety testing.	de Faria et al. [165]
AZ31 Magnesium Alloy	Wire Arc AM (WAAM) Electron Beam AM (EBAM)	Lower porosity and better mechanical properties compared to traditional casting.	Yang et al. [166]. Zhang et al. [167]
Virgin glycol-modified polyethylene terephthalate (PETG) and its carbon fiber-reinforced composite (PETG/CF)	Fused Filament Fabrication (FFF)	PETG/CF sandwich structures demonstrated enhanced energy absorption capabilities in contrast with pure PETG structures, indicating superior structural integrity under impact conditions.	Mallek et al. [168] Mellouli et al. [169] Allouch et al. [170]

lists materials investigated within AM technologies during the last few years.

As AM processes become increasingly standardized, it is very important to provide a methodology to help select the right material for each AM technique. This selection must consider the mechanical and physical properties of the finished product and its specific application. In fact, mechanical requirements such as strength, hardness, flexibility and resistance to fatigue or wear need to be assessed first, in order to guide the choice between different materials such as metals, polymers and ceramics. Thermal properties must then be considered, particularly when the printed product will be operating at high or low temperatures. It is also needed to assess if the selected material is sufficiently compatible with the AM technique, as different technologies such as FDM, SLA or SLS require specific material characteristics. In addition, factors such as surface roughness, layer adhesion and simplicity of post-processing play an important role in this choice. Finally, the availability of the material as well as its cost should not be overlooked, as they can affect the overall feasibility of printing the desired product efficiently and economically. Once the product’s performance requirements are identified, the next step is to translate them into material requirements, i.e., the properties of a material that will meet these performance needs. These parameters could be found on a material’s data sheet.

Table 5. How to select materials for some AM techniques in function of mechanical requirement.

Requirement	Description	Recommendation
Tensile strength	The material’s ability to withstand fracture when subjected to tensile stresses is crucial. The printable material chosen in this case should have a high tensile strength which is essential for components that bear loads, serve structural purposes, or are involved in mechanical or statical functions.	FDM: PLA SLS: Nylon 12, Nylon composites SLA: Clear Resin, Rigid Resins, Alumina 4N Resin
Flexural modulus	The ability of a material to resist bending when subjected to a load. It serves as a good indicator of the material’s stiffness (high modulus) or flexibility (low modulus). The printed components need to be flexible and resistant to a flexural load.	FDM: ABS (medium), PLA (high). SLA: Flexible and Elastic Resins (low), Tough and Durable Resins (medium), Rigid Resins (high). SLS: Nylon 12 (medium), Nylon composites (high).
Elongation	The capacity of a material to resist failure when stretched. It allows for comparison of materials based on their stretchability and indicates whether a material will undergo deformation prior to breaking or fail abruptly. Printed parts should have elasticity to be tough and durable.	FDM: ABS (medium), TPU (high) SLS: Nylon 12 (medium), nylon 11 (medium), polypropylene (medium), TPU (high) SLA: Tough and Durable Resins (medium), Polyurethane Resins (medium), Flexible and Elastic Resins (high), Silicone 40A Resin (high)
Impact strength	The ability of a material to absorb shock and impact energy without fracturing. This property reflects toughness and durability, helping to determine how likely the material is to break when dropped or collided with another object. The printed objects are usually used under some impact conditions.	FDM: ABS, Nylon SLA: Tough 2000 Resin, Tough 1500 Resin, Grey Pro Resin, Durable Resin, Polyurethane Resins SLS: Nylon 12, nylon 11, polypropylene, nylon composites
Hardness	A material’s ability to withstand surface deformation. This helps determine the appropriate level of “softness” for soft plastics such as rubber and elastomers, depending on specific use cases. Flexible materials are preferred in this case of printed products such as rubber materials.	FDM: TPU SLA: Flexible Resin, Elastic Resin, Silicone 40A Resin SLS: TPU
Tear strength	Resistance of material to the expansion of cuts under tension. This characteristic is essential for assessing the durability and tear resistance of soft plastics and flexible substances such as rubber. Printed products made from flexible resin or TPU offer this strength and durability.	FDM: TPU SLA: Flexible Resin, Elastic Resin, Silicone 40A Resin SLS: TPU
Compression set	Permanent deformation after compression indicates whether a material will recover its original shape once the applied load is released. This property is vital for soft plastics and elastic applications, ensuring they maintain their form over time. Which is typical for prints made of flexible resin and TPU as well.	FDM: TPU SLA: Flexible Resin, Elastic Resin, Silicone 40A Resin SLS: TPU
Heat deflection temperature	The temperature at which a material begins to deform under a designated load. This measurement helps determine whether a material is appropriate for use in high-temperature environments. Prints made of Nylon as sample could resist to different loads under higher temperatures.	SLA: High Temp Resin, Rigid Resins, Alumina 4N Resin SLS: Nylon 12, Nylon 11, nylon composites
Creep	Creep refers to a material’s tendency to undergo irreversible deformation when subjected to sustained stress such as tensile, compressive, shear, or bending forces. Low creep rates are desirable for hard plastics, especially in structural components, as they ensure long-term stability and durability. Which is typical for prints made of polyurethane or nylon.	FDM: ABS SLA: Polyurethane Resins, Rigid Resins, Alumina 4N Resin SLS: Nylon 12, nylon 11, nylon composites, polypropylene

gives some recommendations of how to select the right material for FDM, SLA and SLS processes based on the mechanical requirement of the produced part.

AM technologies must overcome several key material-related challenges that hinder their wider adoption and performance. Firstly, the lack of a complete view of material behavior during the additive process leads to discrepancies in mechanical properties, posing a reliability problem for critical applications. Additionally, the AM research community faces the challenge of a wide range of materials being incompatible with AM techniques, which restricts their applicability within many industrial fields such as aerospace and medicine. Nevertheless, future work should give attention to innovation of advanced printable materials, including new composites, nanomaterials, smart materials, and high-performance alloys that are specifically engineered for AM. Furthermore, it is very important to look for a standardization of the processing parameters considering the different references of printable materials which could be classified in function of industrial applications. Enhancing material characterization techniques and establishing standardized testing methods will be crucial as well to ensure consistent quality and accuracy across different AM techniques. Finally, exploring eco-friendly materials and sustainability using recyclable rows and optimizing the recycling processes for AM scraps will be essential for reducing the environmental impact of this process.

2.3. Applications in Various Industries

No one thought that 3D printing technologies would be able to revolutionize so many sectors of industry. While its original function was to speed up rapid prototyping, additive manufacturing has developed over the years, bringing real benefits to different sectors, whether in terms of the materials used, costs or production times. Additive manufacturing is now a recognized and well-established technology in the industrial sector, particularly for prototype development. It has been implemented in several companies and will continuously grow in the near future because it offers unparalleled customization, efficiency, and sustainability in their production lines.

In the aerospace industry, companies such as Boeing have already integrated AM technologies in their processes to produce complex lightweight components, such as the fuel nozzle for the GE LEAP engine shown in Figure 14a [171]. The printed GE’s fuel nozzle boasted a 45% of weight reduction compared to traditionally manufactured parts. With this component the engine performances have been optimized along with a remarkable reduction in the fuel consumption which highlights AM’s role in advancing aerospace technology. Real-world instances can be seen in photos of the A350 XWB’s 3D-printed parts (Figure 14b) [172], which illustrate the successful integration of AM in airframes. Metal additive manufacturing is applied in aerospace to produce functional components such as engine blades, turbines, fuel systems and guide vanes. The topological optimization of parts improves their functionality and reduces their weight. Lighter parts can thus help to lighten aircraft and reduce fuel consumption [173].

Among sectors that use AM technologies, the automotive industry is one of those that benefit the most. This technology enables automakers to reduce costs, manufacturing time, and the weight of increasingly complex parts. Additive manufacturing also enables greater design customization, transforming car models into unforgettable user experiences. Automotive manufacturers such as Ford and BMW are exploiting AM for the prototyping and production of specialized components, particularly in electric vehicles. Ford’s 3D-printed intake manifold illustrates how AM can improve efficiency and reduce production costs while maintaining performance standards. Photographs of this part (Figure 15d) reveal the complex geometries achievable, illustrating the move towards more sustainable automotive designs. Furthermore, BMW’s use of 3D printing for customized jigs and fixtures (see Figure 15a for many samples of car parts made up using the FDM technique) speeds up its production processes considerably, enabling it to respond quickly to market demands. Figure 15 presents some of automotive spare parts made with AM techniques, clearly indicating their high quality and complexity [173].

Table 6. Main materials used for automotive applications.

Materials	Automobile Application	Advantages	Disadvantages
Metals	Gears and other transmission components. Intake manifold. Exhaust system. Chassis parts. Some engine components. Braking components. Customized tunning parts.	Better mechanical proprieties. High strength to weight ratio. Easy to customize compared to conventional processes. Better wear and fatigue resistance. Higher thermal stability. Good resistance to high temperatures and harsh environments.	High cost of materials and machines. Limited choice of materials certainly for high performance utilities. Need post-processing. Some microstructural defects could be present in printed products. Limited design complexity and intricate features.
Polymers	Tooling, jigs, and fixtures. Functional prototypes and testing parts. Customized automotive parts such as drive wheel, gear knob, front grille, etc. Dumpers. Internal doors panels. Customized dashboard components.	Low cost. Fast, easy processing. Suitable for dashboard components and other interior parts. Suitable for complex designs. Good impact resistance. Could reduce cabin noise. Possible for multicolor components.	Limited thermal stability. Limited chemical resistance. Limited mechanical strength. Limited dimensional precision and accuracy. Limited texture resolution. Limited recyclability. Could give off unpleasant odors in the interior cabin.
Ceramics	Wear resistance components. Brake components. Body components for sports cars. Spark plugs and ignition systems. Exhaust systems. Some engine components. Sensors and electronic parts.	Excellent mechanical proprieties. Light weight. Good wear resistance. High temperature resistance. High thermal stability. Low density.	Availability of some ceramic powders. High cost of material and machines. High processing temperatures. Limited design complexity. Challenge to achieve dense and void-free prints due to high temperatures reached during the process.

presents three main materials usually used in the automotive industry along with their advantages and disadvantages remarked from real case products.

Since the 1990s, Additive manufacturing has been increasingly used in the medical field, where it is known as bioprinting. Several companies have pioneered this technology, such as when scientists succeeded in 3D printing a bladder. The American company Organovo, for example, created the first commercially available 3D bioprinter, the NovoGEN MMX. Today, various universities and companies have similar machine models and are pushing ahead with research in this sector. AM technologies offer unlimited customization and is therefore having a major impact on the medical field, where every treatment must be individualized. These technologies are making waves through the development of customized implants and prosthesis as well as some medical tools and devices. A standout sample is the 3D-printed leg orthosis (Figure 16) which offers a custom fit for amputees, significantly improving comfort and functionality. Additionally, 3D-printed metal implants (see Figure 17), such as those used in complex cranial surgeries, exemplify the revolutionary potential of AM to tailor medical devices to individual patient anatomies, resulting in reduced recovery times and improved surgical outcomes [176].

During the COVID-19 pandemic, global demand for essential medical supplies surged dramatically, resulting in critical shortages caused by manufacturing and transportation disruptions. The most urgently needed items were those with the most limited availability, notably personal protective equipment (PPE) and ventilators [177] (refer to Figure 18). The adaptability and rapid deployment capabilities of 3D printing technology allowed it to play a significant role during this crisis, with numerous organizations leveraging printers to produce vital items. An illustrative example is UK-based Photocentric, which utilized its proprietary medical 3D printing technology to swiftly deliver millions of protective masks for frontline personnel. The company’s facility in Peterborough was converted into an efficient, purpose-built manufacturing hub, where a fleet of 45 large-format 3D printers produced over 50,000 components daily. A representative from Photocentric highlighted that this achievement demonstrates the shift in medical 3D printing’s role from slow, costly prototyping to a viable solution capable of mass production when and where it is needed, all at a competitive cost. Ahmed and Azam [178] and Rupesh Kumar et al. [179] reported in their recently published review papers almost all the applications of 3D printing for customized products used as tools in the battle against COVID-19 pandemic.

Table 7. Main materials used for medical applications.

Materials	Medical Application	Advantages	Disadvantages
Metals	Surgical instruments. Implants (e.g., orthopedic, dental). Leg orthosis. Knee joint. Dental fillings. Supportive guides. Splints and prostheses. Tools and medical devices.	High strength and durability. Corrosion resistance. Biocompatibility (certain metals like titanium). Flexibility of design.	High cost. Potential allergies or toxicity (e.g., nickel). Metal fatigue over time. Need periodic control and maintenance. Limited availability. Possibility of material defects with respect to appearance. Need careful post-processing.
Polymers	Artificial joints. Catheters. Surgical gloves. Drug delivery systems. Cranial orthosis. Safety equipment. Dental implants. Wearable prosthesis. Sacral surgery planning.	Lightweight. Flexible. Cost-effective. Easy to sterilize. Flexible in design. Many polymers resist degradation in biological environments.	Limited mechanical strength. Potential for degradation or leaching. Less thermally stable. Less chemical resistance with bodily fluids. Some polymers may deform, degrade or lose their properties when subjected to standard sterilization methods such as autoclaving. Biocompatibility risks.
Ceramics	Dental crowns and bridges. Bone substitutes. Joint replacements. Instruments and tools. Biomimetic scaffolds. Load-bearing applications. Dentistry, coatings and scaffolds. Spinal surgery.	Hard and wear resistant. Biocompatible. High compressive strength. Osteoconductive. Mechanically strong. Nontoxic. Low friction coefficient. Chemical resistance with body. fluids and sterilizers. Sterile nature.	Brittle and prone to fracture. Difficult to shape. Expensive fabrication. Limited availability of some ceramics. Need careful post-processing. Limited use in applications that require. high structural strength. Processing difficulties because ceramics require precise temperature and time conditions.
Composites	Dental restorations. Bone tissue engineering. Scaffolds. Implants. Artificial intervertebral discs. Joint prosthetic surfaces. Surgical retractors and spreader. Endoscopic instruments. Dental drills and braces. Artificial tendons, ligaments, cartilage.	Combines benefits of metals and ceramics. Improved mechanical properties and osteointegration. Versatility. Reproducing the structure, resistance and flexibility of the natural tissue.	More complex manufacturing. Potential issues with long-term stability. Expensive. The design is far more complex than that of conventional monolithic materials. Require special cleaning and sterilization. There are no satisfactory standards yet for the testing of biocompatibility.
Glass	Bioactive glasses for bone regeneration. Contact lenses. Endoscopes and dental instruments. Microscopic slides. Colorless teeth braces.	Biocompatible. Promotes tissue bonding. Transparent. Superior light performance. Strong yet bendable. Stable at high temperatures. High chemical resistance. Design flexibility.	Brittle. Limited mechanical strength. Fracture risk. Achieving precise, high-resolution features in glass via 3D printing can be complex and require advanced, often costly equipment. Less scalable.

lists the main materials along with their applications in 3D-printed products for medical field along with the main advantages and disadvantages remarked during the processing of these products with AM technologies.

The consumer goods sector has also benefited from the flexibility of additive manufacturing technologies. In fact, this sector is also witnessing the evolution of this manufacturing process, which offers new possibilities in terms of durability, creativity and personalization. Three-dimensional printing has made it possible to create garments that fit precisely to the customer’s morphology, making them more comfortable when using these printed products and setting them apart with the design flexibility demonstrated by most additive manufacturing techniques. Three-dimensional printing has also sped up the design and testing process for new collections, enabling on-demand production and reducing textile waste and overproduction. Additive manufacturing technologies have made it possible to incorporate innovative, customized products, such as fashionable garments [180] and beauty accessories [181], which are usually expensive or difficult to manufacture using conventional manufacturing processes. This encourages a more sustainable and experimental approach, inviting us to rethink the way clothes are designed, made and consumed.

Brands of sportswear like Adidas and Nike, that produce customized products on demand, started using AM processes in many customized products, such as the Adidas Futurecraft 4D presented in Figure 19, which shows the intricate lattice structures used to make the footbed of this sports shoes promoting a breathable design, lightweight, and catering to the personalized needs of consumers [180]. Figure 20 shows the capabilities of 3D printing to produce customized jewelry made with perfect details and complex design. In fact, the samples presented in this figure are designed by the company X Over Zero, by designers McLemore Duane and Katherine Voorhies; these sample show how AM technologies could be used to push the boundaries of the possible, to craft objects that test the limits of current technology, and bring to the forefront a new aesthetic that would not otherwise be possible [181].

In the construction industry, the 3D printing process is being used to create innovative smart building materials and structures by using giant 3D printers to create these structures, from walls to entire buildings, via digital models. This approach reduces construction time, costs, environmental impact, and risks on building sites, revolutionizing construction practices and offering efficient and resilient houses to meet the specific cultural and climate needs, particularly of Indigenous communities [182]. A notable example is the ICON 3D-printed homes, presented in Figure 21; the design of these structures highlights the potential to reduce labor costs and construction waste while promoting sustainability and lead building timelines. This sustained home design uses a unique concrete mix and advanced robotic printing techniques at large scales. Furthermore, the use of AM in producing complex architectural components, such as decorative facades, illustrates the blend of art and engineering achievable through this technology.

Additive manufacturing is used in many sectors other than the main ones mentioned above. It is a technology that is revolutionizing our whole society, because it facilitates creation and customization, and responds to precise needs. It allows us to bypass certain obstacles and complexities. Each sector previously cited benefits from AM’s capacity for customization, sustainability, and efficiency, allowing to create innovative products that enhance performance and user experience. As this technology continues to evolve, we can anticipate even greater advancements and broader applications, fundamentally reshaping the future landscape of manufacturing.

3. Challenges of Additive Manufacturing

3D printing offers advantages over traditional methods in several specific areas, such as complex geometries and customization. In fact, it is easy to produce complex, organic, or lightweight lattice structures using 3D printing, which is difficult or impossible to achieve with machining or casting [183]. Three-dimensional printing offers rapid prototyping and iteration, resulting in faster design validation and reduced downtime between concept and tangible part. The process is cost- and material-efficient for low-volume or customized parts. The different AM techniques produce near-net shapes reducing waste and tooling costs. They offer design freedom and customization at scale, allowing them to produce customized or unique components without expensive molds. Integrated and multi-material capabilities use different materials such as composites, polymers with variable properties, or present features that integrate the same structure. AM offers reduced lead times for complex assemblies; the construction of multi-part objects can be replaced by a single print which minimizes assembly steps and tooling [184].

Table 8. Comparison between AM and conventional manufacturing processes.

Aspect	Additive Manufacturing	Conventional Manufacturing
Type of production	They are much more flexible in producing complex geometries, reducing the need for DFM rules. AM techniques can print complex products in a single shot without the need for assembling several components.	Unlike AM processes, conventional subtractive processes are subject to restrictive DFM rules, meaning that the design must be simplified to meet manufacturability requirements.
Productivity	AM is more suited to low-volume production or the manufacture of custom parts and prototypes. Costs increase exponentially with large batch production due to the time and material usage.	Conventional processes are designed for mass production and large batches of single parts and assemblies. These processes are cost-effective for high productivity.
Customization	Customization in the AM process is simple and rapid to produce unique designs with higher complexity at lower costs, making it more suited for prototyping and small-batch production.	Reduced customization capabilities are due to tooling requirements and high costs. Producing unique and complex parts can be very expensive.
Lead Time	AM has better lead times for concept iteration and customization. Printing processes are slower than machining but operate faster with thermosets than with metal materials. It is preferred for prototyping and small-batch production.	Conventional methods often deliver faster per-part throughput and lower cost at scale. But longer lead times are due to tooling, setup, and production processes considering small batches and customization.
Production Costs	There are lower cost for short runs due to no tooling. But the costs rise exponentially if the production rate increases.	There are high costs for small batches, but they become economical with scale. Conversely, the cost will be spread out if production batches increase.
Assemblies	Assemblies can be printed as a single part, which reduces the need for post-production assembly and minimizes imprecisions.	Parts are typically manufactured separately and assembled afterward, requiring additional tooling and time for assembling and adjustment.
Material Selection	There are limited selection of materials based on specific additive techniques (e.g., polymers, metals, or ceramics). Some printable materials pose a durability issue for functional components.	A wider range of materials can be used, including metals, plastics, and composites, offering a better flexibility in terms of material choice.
Sustainability	AM is more sustainable as it produces less material waste, using only the material required to build the part layer by layer. It also enables localized production, reducing transportation emissions.	Traditional manufacturing typically generates more waste through subtractive methods like machining and excess material use, especially in high-volume production.
Manufacturing Equipment	A single 3D printer can produce a wide range of parts, reducing the need for multiple machines or tools. However, some additive manufacturing techniques have high investment costs due to the sophistication of certain metal additive manufacturing printers.	Multiple tools and machines are required for different processes, such as milling, turning, drilling, and forming.
Standards	The standardization of 3D printing techniques still needs to be studied in greater depth. Regulatory issues are currently under review.	The different processes are standardized and do not pose any regulatory issues.

presents a comparison between AM processes and conventional manufacturing processes, explaining the general challenge of AM techniques to compete with conventional processes such as machining especially if the production rate is increased.

Additive manufacturing technologies are still innovative manufacturing processes in the way of development compared to conventional manufacturing processes, requiring further research to improve on the drawbacks that have been noted in various applications. So far, there are many challenges in the way of improving the field of additive manufacturing. These challenges include the following:

3.1. General Challenges

Capital expenditure—The upfront cost of 3D printing equipment, while significant, is generally lower than that associated with traditional subtractive manufacturing techniques (see Figure 22). In this figure, cost per part is compared with the complexity of part for AM and conventional manufacturing processes. If the complexity level is above the break-even point, it would be cost effective to build the part using manufacturing [185].

In the current economic climate, many organizations remain hesitant to commit to large capital expenditures, especially when exploring emerging and rapidly evolving sectors like additive manufacturing. Justifying such investments can be particularly challenging when the primary goal is to accelerate prototype development, as conventional accounting methods often struggle to accurately quantify the immediate or long-term return on investment. This financial uncertainty can hinder widespread adoption, despite the potential efficiencies and innovation benefits that 3D printing offers.

Figure 22. Costs in AM vs. traditional manufacturing [185].

Figure 22. Costs in AM vs. traditional manufacturing [185].

Maintenance—As 3D printing technology continues to advance, equipment failures and breakdowns remain a common challenge, even with routine maintenance. Such interruptions lead to downtime, which can significantly impact productivity and operational efficiency, thereby deterring potential investors concerned about reliability and associated costs. Additionally, due to persistent supply chain disruptions, critical spare parts are often kept in stock as a precaution, which can further elevate the overall ownership costs. These factors highlight the importance of developing more robust and reliable systems, as well as resilient supply chains, to mitigate downtime and reduce long-term expenses, making additive manufacturing more attractive and sustainable for users and investors alike.

Labor shortage—One significant obstacle in the adoption of additive manufacturing is the requirement for specialized technical expertise to operate and manage the equipment effectively. The growing market demand for skilled professionals to oversee AM processes underscores the need for comprehensive training, which often necessitates developing in-house capabilities through external education programs. This training process can be time-consuming and may delay the justified investment in capital equipment. Beyond basic file conversions, mastery of equipment involves a range of labor-intensive tasks, including changing filaments during printing, fine-tuning machine settings, removing support structures, and performing post-processing operations. Addressing these skill gaps is crucial for streamlining workflows, ensuring quality output, and accelerating the integration of AM technologies across various sectors.

Material availability—Considering the relatively nascent stage of additive manufacturing (AM) technologies, the availability of materials remains limited compared to conventional manufacturing methods. The relatively short history of AM materials and the narrower selection currently available present both challenges and opportunities. Despite these limitations, the field of AM materials is advancing steadily, with ongoing research and development driving innovative solutions. This continuous progress promises to expand material options and enhance the capabilities of additive manufacturing, opening up new avenues for customization, efficiency, and performance in various industries.

The AM environment—A fundamental shift in mindset is often necessary for individuals to fully accept and integrate emerging, rapidly evolving technologies. Historically, many investors tend to adopt a reactive stance, choosing to engage only after technological advancements have matured and challenges have been addressed comprehensively. However, this perspective is likely to evolve as ongoing improvements in materials and technological innovations continue to accelerate, broadening the scope of possibilities and influencing future investment strategies. Embracing this proactive approach can unlock significant opportunities and foster greater resilience in adapting to the dynamic landscape of technological progress.

3.2. Technical Challenges of Additive Manufacturing

As with any new technology, several technical challenges remain before most manufacturers adopt the AM industry. These include the following challenges:

Slow production speed—The 3D printing process is known for its slow manufacturing speeds, which prevents it from being used for large-scale production applications. Equipment manufacturers are aware of this shortcoming and are diligently seeking methods to improve production speeds. Selective Laser Sintering (SLS) printers have adopted dual print heads to sinter powder faster. Other prototype printers can apparently print thirty layers simultaneously instead of one. Finally, in-depth research into the development of more productive 3D printers, with the aim of achieving a production time comparable to that achieved by conventional manufacturing processes such as machining. Research should focus on the development of stepper motors used to control the movement of various machine components such as the build plate, and on optimizing the correlation between this speed and print quality and precision. The use of robotic arms in metal additive manufacturing has helped the manufacturer to accelerate productivity and increase the flexibility of the AM process. The study of hybrid processes could yield good results in terms of productivity by combining the advantages of conventional manufacturing processes with the flexibility of AM techniques.

Post-processing automation—Many 3D-printed components necessitate various post-processing procedures to achieve desired quality and functionality. These steps often involve extra labor, thereby increasing the overall cost per unit. Common post-processing activities include substrate removal, mechanical shot peening, cleaning, vapor smoothing, and curing, among others. Automating these processes presents a significant opportunity to enhance efficiency and consistency. The key challenge lies in developing robotic systems and automated handling solutions capable of performing these tasks reliably and accurately, reducing reliance on manual labor, minimizing human error, and streamlining the entire post-processing workflow. Advancements in robotics and automation technology are critical to overcoming these hurdles and making digital manufacturing more scalable and cost effective. Figure 23 shows that post-processing time is longer in AM than in CNC machining or injection molding [186]. AM times still cannot compete with those achieved in injection molding. Although mold manufacturing is time-consuming in injection molding, in mass production, this long time will be spread over the number of parts when these molds are used repeatedly over a long period.

Software—Currently, the scope for data preparation and design capabilities in 3D printing remain somewhat restricted. To optimize their additive manufacturing (AM) processes, companies require a robust digital infrastructure that can efficiently handle various aspects of their operations. Recognizing this need, the industry has developed specialized workflow management software tailored specifically for 3D printing. Such software streamlines and integrates key functions, including handling printing requests, conducting printability assessments, analyzing machine performance, scheduling production tasks, managing post-processing activities, and coordinating communication with suppliers. By implementing these advanced digital tools, companies can improve operational efficiency, reduce errors, and better align their manufacturing processes with dynamic market demands.

Quality—Part-to-part inconsistency remains a significant challenge across many additive manufacturing (AM) technologies. One of the primary sources of this variability is material composition, which can be compromised through contamination. Additionally, storage and handling practices play a role in introducing further variation. To ensure consistent quality, the industry needs standardized testing protocols for materials and handling procedures.

Advances in monitoring technology are crucial for addressing these issues. Integrating cameras and sensors directly into 3D printers enables real-time observation of the manufacturing process. This capability facilitates a shift from traditional open-loop systems, which operate without feedback, to closed-loop control systems that continuously monitor and adjust parameters during production. Such closed-loop systems help maintain consistent geometries, material properties, and surface finishes, ultimately enhancing the overall quality and reliability of printed parts. Figure 24 shows that Typical AM systems improve surface finish by decreasing layer thickness, at the cost of productivity. However, AM+ CNC machines as a hybrid process can achieve the required surface finishes without sacrificing productivity [187], which claims the importance of hybrid AM methods with a secondary subtractive process.

Materials—Material selection has improved considerably, but there is still a long way to go before the computer-aided manufacturing sector outstrips existing technologies. Information on materials is lacking, as there is no comprehensive materials database with established printing parameters and clearly defined specifications. Manufacturers are reluctant to use technology with such information gaps. Problems with the printability of many materials limit the flexibility of AM techniques and reduce availability and supply in industries that could make use of this innovative process. Testing new materials for 3D printing remains a promising area of research aimed at broadening the range and increasing availability. Research such as that presented in the work of Alghamdy et al. [188] could improve the methodology used for selecting AM materials. In fact, a material selection matrix has been developed to classify recommended materials based on criteria weighted according to the AM application. The matrix developed using selection algorithms enables AM users to make informed decisions when selecting materials.

Standards—The challenge of standardization in 3D printing is triggered by the diversity of technologies, materials and software platforms used in this field. Such diverse printing methods, as cited previously and considering that each technique may require specific parameters and equipment, lead to difficulties to create universal standards specific to this field. Variations in filament types, powder compositions and resin formulations could complicate compatibility and quality assurance. Even the use of different file formats and slicing software could cause many inconsistencies in print results. This lack of uniform standards hinders interoperability, scalability, and widespread adoption, making it difficult for manufacturers, designers and end-users to achieve consistent results with different printers and applications. Addressing these standardization issues is critical for advancing the reliability and integration of 3D printing into mainstream manufacturing processes. Some key players in standards development, such as ISO and ASTM International, have set up committees dedicated to the development of AM standards. These standards should consider developing a comprehensive materials database, with established print parameters and clearly defined specifications, as is the case for machining, for example, as well as addressing environmental, healthcare, social, ethical and legal issues.

3.3. Operational and Organizational Challenges of Additive Manufacturing

Additive manufacturing (AM) is a relatively new technology under development, with few historical examples of its implementation on an operational scale specifically in mass production, and few specific business and cost models based on AM are available. Legal concerns over ownership of digital designs also discourage many companies, as does the significant shortage of specialists trained in additive manufacturing. However, the rapid growth in the popularity and adoption of AM is a positive trend. Advances in new materials are enabling AM to replace many traditional subtractive manufacturing methods. The development of universally accepted AM standards will help the industry to expand its manufacturing capabilities. These challenges can often be mitigated by partnering with an experienced 3D printing supplier, which can reduce capital investment and shorten the learning curve. Such collaborations also provide access to a wider range of materials and post-processing techniques. In addition to direct partnerships with manufacturers, many distributed manufacturing companies have local production facilities and can oversee these processes efficiently.

3.4. Environmental Challenges of Additive Manufacturing

Additive manufacturing (AM) can offer environmental benefits for low to moderate production volumes by enabling part consolidation, reduced assembly, and minimized tooling, which can reduce energy consumption, material waste, and intrinsic emissions per part when complex geometries or lightweight designs justify the investment. However, its environmental footprint is highly contextual and often depends on the type of process, material, post-processing, and energy sources. Metal AM (e.g., DMLS/SLM) tends to have higher impacts in terms of energy per part and powder handling but can reduce downstream machining and waste, while polymer AM (e.g., FDM/FFF, SLA) can reduce energy per part but suffers from longer cycle times and post-processing. On the other hand, conventional methods such as casting and injection molding excel in high-volume production with well-established recycling and tooling savings. These traditional methods generally produce fewer emissions per part on a large scale, but with potential waste from sprues, runners, and mold production. Data quality, functional requirements, raw material recyclability, and the combination of energy sources (renewable or fossil) dominate the results, so the LCAs that need to be carried out in this case must clearly indicate the scope, functional unit, and assumptions and include sensitivity analyses on batch size, post-processing intensity, and end-of-life treatment. An example of LCA performed by DeBoer et al. [189], plotted in Figure 25, demonstrates that AM techniques such as Binder Jetting, Bound Powder Extrusion, and Powder Bed Fusion have lower environmental impact in terms of water consumption, energy consumption, and CO₂ emissions in contrast with machining. However, casting, as a conventional process, has the lowest environmental footprint. This can be attributed to the fact that water and energy consumption, as well as CO₂ emissions during the preparation of cast iron as the base material for casting, are significantly lower than those associated with materials used in AM techniques.

To summarize, in spite of the significant benefits of additive manufacturing (AM) technologies, such as material efficiency, design freedom, rapidity of making complex designs using one processing operation, etc., it faces several key challenges. One of challenges is the variability in material properties, which can influence the mechanical and thermal efficiency of prints. Additionally, scaling up production for high volumes remains a hurdle, as many AM techniques are inherently less productive compared to traditional manufacturing methods. Complex geometries usually need a long printing time as well as post-processing to reach a similar quality and precision of, for example, machining. Quality control and standardization are also critical issues that should be raised in the future of AM processes. In fact, ensuring consistent output and compliance with industry standards can be difficult, as the precision of printed products can be compromised in some AM techniques. Furthermore, the technical expertise required to operate advanced AM machines and post-processing techniques is often lacking, limiting widespread adoption across various sectors. Addressing these challenges is essential for the future growth and acceptance of additive manufacturing in different industries. Figure 26 recapitulates the key challenges of this process.

4. Future Directions

4.1. Emerging Technologies

The future development of AM techniques looks very promising, thanks to the integration of several innovative technologies that could radically transform the field into a competitive process that could rival traditional processes in terms of productivity and precision. Among these, hybrid manufacturing, which combines additive manufacturing with conventional manufacturing methods such as welding with its different types or machining, could offer better opportunities to produce complex products, while improving the efficiency, precision, and robustness of the process. The advantages of using hybrid techniques of 3D printing are highlighted in the rise in productivity, decreasing costs, and extending for a wider range of applications in several industrial sectors such as automotive, aeronautics, and healthcare. Moreover, the emergence of AI will play a key role in this transition towards smarter manufacturing. In fact, it will be very easy to optimize the product design, precision and resolution, predict and avoid defects, as well as automate some manufacturing steps such as post-processing thanks to the use of advanced machine learning systems. The fusion of these technologies also facilitates real-time process monitoring, improving final product quality while reducing waste and errors. AI and ML algorithms can accelerate material discovery and property prediction, improve AM process planning by optimizing cutting, substitution simulations, and post-processing. ML algorithms can accelerate convergence toward efficient geometries, particularly when combined with multiphysics simulations. They also enable the exploration of vast design spaces to achieve performance objectives (stiffness, strength, weight, thermal management) while taking into account AM manufacturability. Reinforcement learning or supervised models could adjust parameters (laser power, scan speed, layer thickness) in real time to maintain the required accuracy and resolution.

In addition, advances in smart materials, advanced robotics and automated production will facilitate the widespread adoption of these new techniques. Thanks to the adoption of these innovations, AM techniques could be more flexible, productive and precise, by reaching new possibilities for creating customized parts, reducing environmental impact and transforming manufacturing production on a global scale.

4.2. Four-Dimensional Printing

4D printing is a fascinating development in additive manufacturing, which goes beyond the simple creation of three-dimensional objects. Three-dimensional printing techniques combined with intelligent materials, supported by mathematical modeling and machine-learning algorithms, give rise to three-dimensional objects that have the particularity of evolving over time, in contact with their environment. The result offers an unprecedented degree of structural autonomy, since these 4D-printed structures evolve without any on-board computing power, which means that by incorporating the dimension of time, printed structures are enabled to change shape or functionality in response to environmental stimuli such as heat, humidity or light. The innovative idea of incorporating the fourth dimension to make the process more flexible and sustainable has attracted many researchers in recent years, such as [190,191,192,193,194], but further research into this key topic is still needed for the future of the AM field. In fact, 4D printing leverages stimuli-responsive materials such as shape memory polymers, liquid crystal elastomers, hydrogels, and smart composites subjected to a controlled and reversible transformations powered by external triggers, including temperature, light, humidity, and electric or magnetic fields [190]. These intelligent structures can deploy, self-repair or adjust autonomously [191], opening up innovative possibilities in many applications. For example, medical implants [192], skin tissue [193], or construction materials [194] could evolve to adapt to their case of use and environment, which improve the durability and efficiency of solutions. Four-dimensional printing represents a promising step in the innovation of self-adaptive systems, offering considerable potential for transforming the way we design, manufacture and use objects in the future.

Table 9. Four-dimensional printing during the last few years.

Type of AM	Materials	Main Findings	Application	References
DLP, FFF, FDM	Shape memory polymers (SMPs). Shape memory polymers composite (SMPCs).	Demonstrated an ability to change shape in a programmable manner when exposed to temperature stimuli. When printed objects were subjected to heat, their shape could be temporarily altered and then restored after reheating.	Smart patches for movement detection in artificial limb joints or robotic arms; platform structures; infinity rings, or cubic grids; biomedical devices	Alam et al. [195] Spiegel et al. [196] Kumar et al. [197]
Inkjet-based 4D printing	Liquid crystal elastomers (LCEs). LCE composites with continuous fiber reinforcement.	Demonstrated high actuation forces with reversible shape change. By adding fiber reinforcement, it proved an improved energy absorption and protection capabilities.	Robotics, wearable electronics, artificial muscles, etc.	Jiang et al. [198] Javed et al. [199] Chen et al. [200]
SLA	Hydrogels, shape memory resins.	Reversible deformation capabilities: the shape memory and self-healing properties of hydrogels can be activated almost magically at a temperature close to body temperature by adjusting the molar ratio of the monomers.	Various biomedical applications.	Abdullah and Okay [201] Liu et al. [202]
SLM	Shape memory alloys such as metal nickel and titanium.	Development of mechanical metamaterials able of secure information steganography and display functions. Offers greater environmental adaptability, ease of transport and storage, and excellent response characteristics.	Devices that adapt to complex environments.	Liu et al. [203]
DIW, FFF, SLA, SLS	Electroactive materials such as carbon-based composites, metal nanoparticles, polyelectrolyte hydrogels, conductive inks.	The use of these electrically conductive smart materials is promising for electronic devices such as sensors and robotics. Printed composites, for example, allow control of their own stiffness between flexible and rigid states thanks to the effective LM phase transition, which is beneficial in soft sensing actuators applications.	Soft actuators, smart textiles, chemical and fluid sensors, printable circuits	Long et al. [204] Wang et al. [205] Shin et al. [206]
DLP, DIW	Ceramic-based smart materials.	Wang et al. [207] implemented a method using a mixture of photopolymerizable ceramic elastomer with a hydrogel precursor to fabricate hydrogel–ceramic laminates by 4D printing. The results are promising for overcoming the challenge of printing ceramics due to their extremely low deformability. Wang et al. [208] found that it could be possible to tailor the shape-morphing behaviors of ceramic structures by routing the printing process.	Hydrogel–ceramic laminates, printed ceramic flowers.	Wang et al. [207] Wang et al. [208]
DIW	Phase change materials.	Phase change materials (PCMs), which change their state in response to stimuli such as heat, are a key component of 4D printing. These materials, combined with other stimulus-sensitive materials, enable the creation of 4D-printed objects capable of adapting to environmental changes or external forces.	Soft robotics and flexible electronic devices, flexible grippers, load-bearing dome structures.	Zheng et al. [209] Mehta and Sahlot [210]

recapitulates the main findings during the last few years in this promising technique.

4.3. Trends in Materials Science for AM Applications

AM technologies keep pace with developments and new innovations in materials science, resulting in the use of the latest trends in materials, such as bio-based [211,212,213,214] and smart materials [215,216,217,218]. The aim of AM is to improve the process and make it more flexible and sustainable by developing more functional, durable, and adaptable products. Bio-based materials, derived from renewable sources, are being used in many AM techniques to produce eco-friendly solutions in many sectors such as biomedical devices, packaging and consumer goods, in line with the global emphasis on sustainability. Smart materials are substances that can react dynamically to environmental stimuli like stress and temperature by changing their physical properties, such as color, shape, or conductivity. These changes are often controllable and reversible, making them adaptable and versatile for various applications. Three-dimensional printing is starting to use these materials to produce adaptive structures with self-repairing, sensing capabilities, and shape-changing at the aim of expanding the functional scope of their printed products. Future directions for additive manufacturing may focus on the use or implementation of sustainable and recyclable bio-based materials, the development of multi-material and functional printing for more complex and integrated solutions, and the incorporation of intelligent functionality into printed structures.

4.4. Potential Impacts on Supply Chain and Production Models

The future of 3D printing is set to have a profound impact on supply chains and production models, enabling a shift towards more decentralized and flexible manufacturing systems that help optimize and reduce manufacturing times in many cases, resulting in lower costs. The use of this technology can facilitate localized, on-demand production, remarkably reducing the need for vast inventories and warehouses, and minimizing the complexities associated with global logistics and transport costs. Certainly, by enabling companies to produce complex parts and customized products directly at or near the point of use, 3D printing improves responsiveness to changing market demands and reduces lead times, fostering a more flexible and resilient supply chain. The simple idea is that, using a 3D printer, one can manufacture spare parts for corrective maintenance while eliminating costly machine downtime. Furthermore, as technology advances, it will promote rapid prototyping and iterative design that can be tailored to changing needs, speeding up innovation cycles and enabling faster adaptation to customer preferences and changing requirements. The ability to manufacture easily customizable products locally without recourse to external sourcing can also reduce dependence on long supply routes, which can be disrupted by geopolitical problems or global crises, increasing the overall robustness of the supply chain. In addition, 3D printing’s ability to reduce waste compared with conventional manufacturing processes such as machining, which produce quite a lot of material loss, as well as AM’s ability to use recyclable materials, aligns with sustainable development objectives, making supply chains more environmentally friendly. Overall, the integration of 3D printing into mainstream manufacturing could transform traditional models into more localized, customized, sustainable and environmentally friendly systems, fundamentally redefining global production and distribution networks.

4.5. Scalability

Future directions in the scalability of additive manufacturing (AM) are poised to revolutionize industrial production by tackling current limitations related to speed, cost and material diversity. Key advances include the development of high-throughput manufacturing systems capable of simultaneously printing larger parts or multiple components, such as the use of advantageous conventional processes like wire arc-welding [219,220,221,222] in additive processes, thus significantly boosting productivity. Automation technologies, such as robotic handling and intelligent process control, will further streamline production flows and reduce labor costs. In addition, research into new multifunctional materials and composite filaments will expand AM’s capabilities, enabling the manufacture of complex, high-performance parts. The integration of digital twin technology, artificial intelligence and machine learning algorithms will play a crucial role in real-time process monitoring, quality assurance and predictive maintenance, ensuring consistency and reducing waste. In addition, efforts to standardize processes and develop industry-wide certifications will encourage wider adoption of scalable AM solutions. As these developments unfold, additive manufacturing is set to become the cornerstone of large-scale, flexible and sustainable production systems, bridging the gap between prototyping and full commercial manufacturing.

4.6. Future Research Directions

In line with future directions, research opportunities in the field of additive manufacturing are diverse and very promising, as this innovative process is still under development and several areas could be the subject of further study. Here are some key areas of research that will be of interest for the future of this process:

Material innovation: Expanding the range of printable materials through in-depth research into the development of new functional materials, including metals, biomaterials, composites, and smart materials, offering better printability, improved mechanical performance, and enhanced biocompatibility, in addition to the need of innovating advanced techniques to manufacture products from multiple materials and gradients with complex geometries and customized properties, is very interesting.

Process optimization and control: Given the drawbacks of non-productivity and inaccuracy in many cases, it is important to conduct research into innovative ways to improve accuracy, speed, and reliability through advanced process monitoring, real-time feedback systems, and the integration of machine learning.

Sustainability and eco-friendly AM: As with all manufacturing processes, it is important to focus on research aimed at reducing waste, energy consumption, and the use of recyclable and biodegradable materials for green manufacturing and sustained industry.

Scaling up and industrial integration: It is important to address the challenges of large-scale production, given that additive manufacturing is currently dedicated to the production of small- and medium-scale prototypes and considering high-volume manufacturing’s seamless integration into existing manufacturing ecosystems.

Hybrid additive manufacturing: According to several studies published in recent years, combining additive manufacturing with conventional manufacturing processes such as welding or machining promotes productivity and lead to better accuracy, improving surface finish, and higher functional complexity.

Design for additive manufacturing (DfAM): The development of design principles and specialized software aims to maximize the benefits of AM, including topological optimization and lattice structures.

Advanced post-processing techniques: the idea is to invent new post-processing methods that help improve the surface quality, mechanical properties, and functionality of printed products.

In situ and real-time monitoring: For quality assurance purposes, it is needed to test the use of sensors and artificial intelligence for in situ defect detection, quality assurance, and process validation.

Biomedical applications: It is important to continue to conduct advanced research with the aim of improving personalized medicine, bioprinting, and tissue engineering for healthcare solutions.

Regulatory and standardization frameworks: As mentioned previously, it is very important to establish standards, certifications, and best practices in terms of safety, quality, and reliability for parts manufactured using additive manufacturing, with the aim of producing products that comply with standards in the same way as all conventional manufacturing processes.

5. Conclusions

The present review provides a comprehensive overview of the most recent advances (certainly in the last few years 2022–2025) in the field of additive manufacturing (AM), covering technological, material and application perspectives. It effectively delineates the various additive manufacturing technologies, elucidates the range of materials used and highlights multifaceted industrial applications, offering valuable insight into the current landscape. Looking ahead, the discussion of emerging technologies, including 4D printing, and advances in materials science, lays a promising foundation for future exploration. The focus on how these innovations could transform supply chains and manufacturing paradigms fits well with industry forecasts. Nevertheless, future research should prioritize interdisciplinary approaches, integrating materials science, design and manufacturing processes to accelerate technological maturation and industrial integration. To move forward, it will be essential to encourage standardization, address scalability issues and expand research into sustainable and intelligent additive manufacturing systems to fully unlock the transformative potential of this technology across diverse sectors. Finally, these conclusions can be drawn up:

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Additive manufacturing enables the design and production of complex, customized parts, adapted to specific needs respecting environmental, healthcare and social conditions.

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By building layer by layer, additive manufacturing reduces raw material waste, which is often greater in traditional processes.

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Additive manufacturing can solve the problem of stocking raw materials or spare parts by manufacturing on demand and on site, without the need for long, costly supply chains.

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The cost of equipment, production time and limited choice of materials remain challenges for the wider adoption of this technology.

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Additive manufacturing continues to progress, paving the way for new applications and products, particularly to produce more smart, functional, sustained products in many fields such medicine, aeronautics, automotive and consumer goods.

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Research and development are needed to improve the performance, accessibility, scalability and cost-effectiveness of additive manufacturing.

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AM technologies should focus on the implementation of sustainable and recyclable Bio-based materials, the development of multi-material and functional printing for more complex and integrated solutions, and the incorporation of intelligent functionality into printed structures.

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4D printing represents a promising step in the innovation of self-adaptive systems for more smart printed structures that meet healthcare and environmental requirements.

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The standardization of AM technologies and the development of industry-wide certifications will encourage wider adoption of scalable AM solutions.

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The study of hybrid techniques used in 3D printing is a promising topic which should enable the process to be developed further and made more flexible.