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Advances in Additive Manufacturing: Processes, Systems, and Emerging Horizons

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A special issue of Machines (ISSN 2075-1702). This special issue belongs to the section "Advanced Manufacturing".

Deadline for manuscript submissions: 31 May 2026 | Viewed by 5375

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Dr. Wenchao Zhou

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Guest Editor

Department of Mechanical Engineering, University of Arkansas, Fayetteville, AR 72701, USA
Interests: additive manufacturing; robotics; inkjet

Special Issue Information

Dear Colleagues,

Additive manufacturing (AM) and 3D printing are transforming industries by enabling complex geometries, design innovations, and rapid production. As AM transitions from prototyping to scalable manufacturing, challenges persist in optimizing processes, integrating intelligent systems, and bridging digital design with physical production. This evolution demands innovations across materials, hardware, software, and emerging paradigms such as AI-driven automation, hybrid workflows, and adaptive production strategies.

This Special Issue of Machines focuses on advances in AM technologies that address these challenges while exploring new frontiers. We invite contributions on novel processes, systems, and applications that push the boundaries of AM’s capabilities, including but not limited to the following:

Process Innovations:

Advances in metals, polymers, ceramics, composites, and multi-material printing;
Hybrid manufacturing (integration with subtractive, formative, or assembly processes);
High-speed, large-scale, and micro/nano-scale AM.

Systems and Automation:

AI/ML for design optimization, process control, and defect prediction;
Digital twins, real-time monitoring, and closed-loop feedback systems;
Software tools for generative design, topology optimization, slicing, and workflow automation and integration;
Hardware advancements (e.g., multi-axis printing, modular systems, in situ sensing).

Emerging Frontiers:

Cooperative 3D printing;
Swarm manufacturing (multi-agent manufacturing);
General-purpose, reconfigurable production systems;
Sustainable AM (energy-efficient processes, recyclable materials, circular economy).

We welcome original research, reviews, and case studies that advance AM’s scientific foundations, technological maturity, and industrial relevance. Submissions exploring software/hardware integration, AI-driven workflows, or novel paradigms (e.g., cooperative/swarm manufacturing) are also encouraged as part of AM’s broader evolution.

Dr. Wenchao Zhou
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 250 words) can be sent to the Editorial Office for assessment.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Machines is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

additive manufacturing
3D Printing
hybrid manufacturing
cooperative 3D printing
swarm manufacturing
AI-driven manufacturing

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Published Papers (10 papers)

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Research

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10 pages, 60581 KB

Open AccessArticle

On the Effect of Powder Particles on Tool Wear and Surface Roughness in Hybrid Additive Manufacturing of Inconel 718

by David Sommer, Abdulrahman Safi, Cemal Esen and Ralf Hellmann

Machines 2026, 14(5), 466; https://doi.org/10.3390/machines14050466 - 22 Apr 2026

Viewed by 254

Abstract

We report on tool wear and surface roughness for hybrid additive manufacturing of Inconel 718 components. The hybrid additive manufacturing comprises laser powder bed fusion (PBF-LB/M) and an in situ high-speed milling process, i.e., milling is performed within the powderbed, which deteriorates the surface quality by additionally occurring wear mechanisms. Therefore, in this comparative study milling path suction is used to improve tool wear characteristics and thus enhance surface quality. As a result, we quantify the improvement of the maximum tool life according to the flank wear, which is granted by the milling path suction. Additionally, the dominant wear mechanisms are investigated, revealing adherence and abrasion as the main contributing factors to wear. Furthermore, surface analysis shows an improvement of surface quality by the use of the milling path suction. Specifically, a reduction in surface roughness of hybrid manufactured Inconel 718 components down to a minimum of

R a

= 0.55 μm is highlighted. Full article

(This article belongs to the Special Issue Advances in Additive Manufacturing: Processes, Systems, and Emerging Horizons)

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39 pages, 11175 KB

Open AccessArticle

Automatic Calibration of Robotic 3D Printer Swarms for Cooperative 3D Printing

by Swaleh Owais, Charith Oshadi Nanayakkara Ratnayake, Ali Ugur, Zhenghui Sha and Wenchao Zhou

Machines 2026, 14(4), 443; https://doi.org/10.3390/machines14040443 - 16 Apr 2026

Viewed by 280

Abstract

Cooperative 3D printing (C3DP) is an additive manufacturing paradigm where a swarm of robotic 3D printers work cooperatively in a shared environment to fabricate continuous parts. Reliable operation requires both accurate per-printer kinematic calibration and cross-printer spatial alignment. This paper presents an automatic vision-based XY calibration workflow for C3DP using ArUco fiducials and low-cost monocular cameras. The method performs intra-printer kinematic calibration and inter-printer alignment through peer-to-peer observations without fixed global infrastructure. In a two-printer Selective Compliance Assembly Robot Arm (SCARA) Fused Filament Fabrication (FFF) testbed, the automatic workflow reduced total calibration time from 157.19 min (manual) to 36.49 min while improving positional consistency and print accuracy. For individual-printer artifacts, the mean Euclidean error was 0.03 ± 0.02 mm, whereas cooperative artifacts exhibited a mean Euclidean error of 0.078 ± 0.002 mm. These results show that practical and repeatable C3DP calibration can be achieved with low-cost vision hardware. Full article

(This article belongs to the Special Issue Advances in Additive Manufacturing: Processes, Systems, and Emerging Horizons)

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15 pages, 10645 KB

Open AccessArticle

Investigation into Mechanical Properties and Microstructure of Heat-Treated Hastelloy-X Thin Wall Specimens Obtained by Laser Powder Bed Fusion

by Niccolò Baldi, Alessandro Giorgetti, Lokesh Chandrabalan, Giulio Carcasci, Gabriele Arcidiacono, Paolo Citti and Marco Manetti

Machines 2026, 14(4), 364; https://doi.org/10.3390/machines14040364 - 26 Mar 2026

Viewed by 446

Abstract

This paper investigates how the thickness of dogbone tensile specimens made from heat-treated Hastelloy-X alloy produced by Laser Powder Bed Fusion (LPBF) influences their mechanical properties and microstructure. The focus of the investigation is on surfaces in an “as-built” condition and considers a range of thickness from 3 to 1 mm. The “as-built” surfaces condition is a fundamental outcome, considering that LPBF technology’s key feature is the ability to produce intricate and complex geometries that are difficult to achieve with conventional manufacturing technologies. The specimens were fabricated according to ASTM E8/E8M-21 and were heat-treated in a vacuum furnace at 1150 °C for two hours. The microstructure of the material was evaluated through porosity, EBSD, and Microhardness analyses. The mechanical properties were evaluated through tensile tests conducted at room temperature on dogbone specimens fabricated both parallel and perpendicular to the building direction. The findings indicate a significant reduction in mechanical properties that could be correlated with the reduction in specimen thickness, reflecting a gradual decline from the baseline. Specifically, a 14% decrease in Ultimate Tensile Strength (from 612 to 528 MPa), an approximately 19% reduction in Young’s Modulus (from 190 GPa to 153 GPa), and a 32% decrease in Elongation at Break (from 59.2% to 40.0%) were observed. Furthermore, it was noted that the printing orientation of the specimens significantly affects their mechanical properties, regardless of thickness. Overall, the results suggest that applying standard heat treatment under specific conditions, such as with a thin, exposed wall of about 1mm with a striped strategy, may not lead to adequate material performance. Full article

(This article belongs to the Special Issue Advances in Additive Manufacturing: Processes, Systems, and Emerging Horizons)

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16 pages, 3508 KB

Open AccessArticle

Melt Electrowriting-Based Hybrid Fabrication of Biodegradable Cog Threads: Design and Mechanical Evaluation for Pelvic Floor Repair

by Fábio Pinheiro, Henrique Leon Bastos, Ana Telma Silva, Nuno Miguel Ferreira, Joana Pinheiro Martins, Maria Francisca Vaz, António Augusto Fernandes, Ana Colette Maurício, Nuno Alves and Maria Elisabete Silva

Machines 2026, 14(3), 301; https://doi.org/10.3390/machines14030301 - 6 Mar 2026

Viewed by 469

Abstract

Additive manufacturing (AM) offers new opportunities for biomedical device design; however, its translation to soft-tissue reinforcement remains challenging, particularly in pelvic organ prolapse (POP) applications requiring mechanical performance and tissue compatibility. In this study, a hybrid AM approach combining melt electrowriting (MEW) and controlled post-processing was developed to fabricate biodegradable poly(ε-caprolactone) (PCL) cog threads for minimally invasive pelvic reinforcement. This integrated fabrication workflow enables the precise deposition of microscale fibers via MEW followed by localized mechanical modification, offering a versatile platform for tailoring graft architecture and anchoring geometry. Smooth filaments were first produced via MEW and subsequently post-processed to introduce barbs for mechanical anchorage. The resulting structures were mechanically characterized through uniaxial tensile testing and evaluated as reinforcement elements in ex vivo sow vaginal tissue using ball burst testing. The MEW-fabricated cog threads increased the ultimate load of vaginal tissue from 83 ± 20 N (control) to 126 ± 15 N, corresponding to a 51.8% improvement (p = 0.0477). Compared with commercial PCL cog threads reported in the literature (177.0 ± 5.4 N), the reinforced specimens achieved approximately 71% of the benchmark load. Owing to their intermediate stiffness profile, the MEW-fabricated cog threads reduced mechanical mismatch with soft tissue compared to high-stiffness commercial alternatives. These findings demonstrate the feasibility of hybrid MEW-based additive manufacturing strategies for engineering mechanically compatible, application-driven soft-tissue reinforcement systems. Full article

(This article belongs to the Special Issue Advances in Additive Manufacturing: Processes, Systems, and Emerging Horizons)

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23 pages, 6364 KB

Open AccessArticle

Prediction of Slurry Erosion–Corrosion in SLM-Produced Ti-6Al-4V Using ANFIS Modeling: Influence of Impact Angles and Erodent Mass

by Saleh Ahmed Aldahash, Ibrahem Maher, Yasser Abdelrhman and Osama Abdelaal

Machines 2026, 14(3), 298; https://doi.org/10.3390/machines14030298 - 6 Mar 2026

Viewed by 489

Abstract

Understanding erosion–corrosion mechanisms in selective laser-melted (SLM) Ti-6Al-4V is essential for optimizing component durability in demanding sectors such as oil and gas, hydropower, and offshore engineering, where slurry-induced degradation prevails. Nevertheless, it is challenging to experimentally evaluate slurry erosion–corrosion over a wide range of SLM processing parameters and various slurry erosion–corrosion operating conditions. The adaptive neuro-fuzzy inference system (ANFIS) offers a robust computational approach for modeling complex systems with independent variables, making it well suited for this investigation. This study aims to assess the efficacy of ANFIS in predicting the mass loss of as-built SLM-processed Ti-6Al-4V under slurry erosion–corrosion conditions, with a focus on the synergistic effects of impact angle and erodent mass in both saline and pure water environments, validated against empirical data. The quantitative analysis reveals that erodent mass is the dominant factor influencing mass loss, followed by impact angles. Notably, the combined effect of erodent mass and impact angles in saline environments (e.g., sea water) exacerbates material loss by approximately 16% compared to pure water, highlighting the critical role of electrochemical corrosion in synergy with mechanical erosion. The results demonstrate that the ANFIS model accurately simulates the degradation behavior of SLM-processed Ti-6Al-4V subjected to water–silica slurry impacts within the experimental parameter space; however, predictive generalization beyond these conditions should be interpreted carefully due to validation constraint. Full article

(This article belongs to the Special Issue Advances in Additive Manufacturing: Processes, Systems, and Emerging Horizons)

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31 pages, 20691 KB

Open AccessArticle

Wire–Laser Additive Manufacturing of Inconel 718 Claddings on S355 and 304L Steels: Process Window and Heat Treatment Optimization

by Carlos D. Mota, André A. Ferreira, Aida B. Moreira and Manuel F. Vieira

Machines 2026, 14(3), 281; https://doi.org/10.3390/machines14030281 - 2 Mar 2026

Viewed by 507

Abstract

Wire–Laser Additive Manufacturing (WLAM) is a promising directed energy deposition technique for producing and repairing high-performance components with high material efficiency and strong metallurgical bonding. This study optimizes single-track Inconel 718 claddings deposited by WLAM on AISI 304L stainless steel and S355 structural steel substrates, focusing on the relationships between processing parameters, microstructure, post-deposition heat treatment, and mechanical performance. A systematic parametric assessment evaluated the influence of laser power, laser speed, wire feed rate, and shielding gas pressure on key quality metrics, including dilution, wettability, porosity, and cracking. Distinct optimal processing windows were identified for each substrate, reflecting their different thermal responses: for 304L, 8.5 kW laser power, 0.55 m/min laser speed, 5 m/min wire feed rate, and 2 bar argon; for S355, 9.6 kW laser power, 0.6 m/min laser speed, 4.9 m/min wire feed rate, and 4 bar argon. Post-deposition heat treatment markedly enhanced performance by dissolving Nb-rich interdendritic Laves phase and promoting γ′/γ″ precipitation. As a result, clad hardness increased from ≈225 HV 0.3 (as-built) to ≈412 H V0.3 after heat treatment (+84%). Tensile testing confirmed substantial strengthening, with yield strength increasing from 447 to 853 MPa (horizontal build) and from 488 to 960 MPa (vertical), while ultimate tensile strength rose from 824 to 1057 MPa (horizontal) and from 836 to 1090 MPa (vertical). Mechanical anisotropy remained significant, linked to columnar grain morphology and build orientation. Overall, the results provide practical process window and heat treatment guidelines for reliable industrial implementation of high-quality Inconel 718 claddings on steel substrates for demanding applications. Full article

(This article belongs to the Special Issue Advances in Additive Manufacturing: Processes, Systems, and Emerging Horizons)

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14 pages, 4474 KB

Open AccessArticle

In-Process Evaluation of Deposition Efficiency in Laser Metal Deposition

by Andrea Angelastro, Marco Latte, Marco Mazzarisi, Maria Grazia Guerra, Luigi Maria Galantucci and Sabina Luisa Campanelli

Machines 2026, 14(2), 182; https://doi.org/10.3390/machines14020182 - 5 Feb 2026

Viewed by 572

Abstract

Laser Metal Deposition (LMD) is an advanced Additive Manufacturing (AM) technology widely used for metal component fabrication, cladding, and repair. Despite its potential, issues such as geometrical inaccuracies and deposition flaws can significantly affect part quality and process efficiency. Existing optical monitoring approaches mainly focus on geometric features and generally do not provide real-time estimates of deposition efficiency, which is critical for both product performance and resource utilization. Furthermore, evaluating deposition efficiency in industrial settings is often time-consuming and difficult to implement. This preliminary study introduces an innovative in-process methodology for assessing deposition efficiency during multi-track deposition. The approach exploits end-track scan data acquired by a laser line scanning system to estimate the deposited volume and the corresponding deposition efficiency for each track. A validation test on a two-layer sample demonstrates the capability of the method to detect defects induced by partially clogged and non-clogged nozzle conditions. Comparison with metallographic measurements shows an average deviation of 4.3%. By enabling timely identification of powder feeding anomalies and supporting improved powder utilization, the proposed methodology contributes to waste reduction, enhanced process stability, and more sustainable industrial implementation of LMD. Full article

(This article belongs to the Special Issue Advances in Additive Manufacturing: Processes, Systems, and Emerging Horizons)

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13 pages, 3845 KB

Open AccessArticle

Investigation of Sintering Parameters for Low-Cost 3D-Printed Cast Iron Using Material Extrusion

by Matthew Drummond, Gillian MacLean, Abdelkrem Eltaggaz and Ibrahim Deiab

Machines 2026, 14(2), 166; https://doi.org/10.3390/machines14020166 - 2 Feb 2026

Viewed by 463

Abstract

Metal Material Extrusion (MEX/M) provides a rapid, low-cost additive manufacturing option for individual and batch productions; however, cast materials are not typically available in the material pool. White cast iron is subject to long casting lead times and high foundry costsThis research details a comparative sintering process study for MEX/M printed white cast iron, a novel addition to the metal additive manufacturing field. A mechanical properties and microscopic evaluation on MEX/M white cast iron samples was completed to compare the influence of three sintering parameters: peak sintering temperature, dwell time, and cooling process. It was observed that increasing the peak sintering temperature increased the sintered density by 23.2% and the volumetric shrinkage by 14.25%. A longer dwell time increased the sintered density by 30.1% and the volumetric shrinkage by 9.42% but decreased the microhardness of the sample. A change in the cooling process of the sample had no effect on the mechanical properties or the microstructure of the sample. The samples achieved a 79.9% increased average density after sintering to 5.75 g/cc, with 57.82% volumetric shrinkage and a 23.3% mass loss. Overall, the samples were 85.8% less dense than casted white cast iron but showed features of a white cast iron microstructure. Full article

(This article belongs to the Special Issue Advances in Additive Manufacturing: Processes, Systems, and Emerging Horizons)

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16 pages, 331 KB

Open AccessArticle

Multi-Criteria Selection of FFF-Printed Gyroid Sandwich Structures in PLA and PLA–Flax Using AHP–TOPSIS

by Mariasofia Parisi and Guido Di Bella

Machines 2026, 14(2), 162; https://doi.org/10.3390/machines14020162 - 1 Feb 2026

Cited by 1 | Viewed by 537

Abstract

Additive manufacturing enables lightweight sandwich structures with complex cellular cores, but the selection of material and process settings typically involves trade-offs among mechanical performance, cost, and sustainability. This study proposes an integrated multi-criteria decision-making framework to identify the most suitable configuration for Fused Filament Fabrication (FFF) sandwich structures featuring a gyroid triply periodic minimal surface (TPMS) core. Eight alternatives are evaluated by combining two materials (PLA and PLA–Flax biocomposite) with two extrusion temperatures (200 °C and 220 °C) and two infill densities (20% and 30%). Mechanical performance is represented by flexural strength obtained from three-point bending tests reported in a previously published experimental campaign, while economic and environmental indicators are quantified through material cost and printing energy consumption, respectively. Criteria weights are derived using the Analytic Hierarchy Process (AHP) based on expert judgment and consistency-ratio verification, and the alternatives are ranked using the TOPSIS method. The results highlight a clear dominance of PLA-based configurations under the adopted weighting scheme, with PLA printed at 200 °C and 20% infill emerging as the best compromise solution. PLA–Flax options are penalized by higher material cost, higher printing-process energy demand, and lower flexural strength in the investigated conditions. The proposed AHP–TOPSIS workflow supports transparent, data-driven selection of AM process–material combinations for gyroid sandwich structures, and it can be readily extended by including additional sustainability metrics (e.g., CO₂-equivalent) and application-specific constraints. A sensitivity analysis under alternative weighting scenarios further confirms the robustness of the obtained ranking. Full article

(This article belongs to the Special Issue Advances in Additive Manufacturing: Processes, Systems, and Emerging Horizons)

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Review

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44 pages, 11137 KB

Open AccessReview

Cold Metal Transfer-Based Wire Arc Additive Manufacturing of Al–Si Alloys: Technology Principles, Process Control, Material Behaviour and Defect Formation

by Gabriela Rodríguez-García, Jorge Salguero, Moisés Batista, Leandro González-Rovira and Irene Del Sol

Machines 2026, 14(4), 421; https://doi.org/10.3390/machines14040421 - 10 Apr 2026

Viewed by 507

Abstract

Wire Arc Additive Manufacturing (WAAM) has gained attention as a metal additive manufacturing process producing complex large-scale components with high deposition rates and lower costs. Cold Metal Transfer (CMT) offers reduced heat input and enhanced control of metal transfer, making it suitable for aluminium. This review analyses CMT-based WAAM with a focus on Al–Si alloys, providing a synthesis for this material system and establishing a structured comparison of representative studies on process fundamentals, arc mode variants, and key processing parameters. The influence of electrical and kinematic parameters and thermal management on process and geometrical stability, microstructural evolution, defect formation, and mechanical behaviour is discussed. Process behaviour is governed by the temporal distribution of heat input within the CMT cycle and thermal history. Control of heat input can reduce porosity, microstructural heterogeneity, and geometric instability, while advanced CMT modes can improve process stability and material efficiency under appropriate process configurations. Mechanical performance depends on the interaction between process parameters, microstructure, and defects, leading to variability and anisotropy. Despite progress, challenges related to process repeatability, narrow processing windows, defect susceptibility, and predictive capability remain. Future research should focus on parameter optimization, integrated modelling, real-time control, and WAAM-specific alloys to enable reliable industrial implementation. Full article

(This article belongs to the Special Issue Advances in Additive Manufacturing: Processes, Systems, and Emerging Horizons)

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