Journal of Manufacturing and Materials Processing

23 pages, 1137 KiB

Open AccessArticle

On the Use of Compressed Air and Synthetic Biodegradable Cutting Fluid to Enhance the Surface Quality of WAAM–CMT Manufactured Low-Alloy Steel Parts During Post-Processing Milling with Different Cooling–Lubrication Strategies

by Déborah de Oliveira, Marcos Vinícius Gonçalves, Guilherme Menezes Ribeiro, André Luis Silva da Costa, Luis Regueiras, Tiago Silva, Abílio de Jesus, Lucival Malcher and Maksym Ziberov

J. Manuf. Mater. Process. 2025, 9(6), 193; https://doi.org/10.3390/jmmp9060193 - 10 Jun 2025

Abstract

Additive manufacturing (AM) stands out for its variable applications in terms of material, quality, and geometry. Wire Arc Additive Manufacturing (WAAM) is remarkable for producing large parts in reduced times when compared to other AM methods. The possibility of producing a part with [...] Read more.

Additive manufacturing (AM) stands out for its variable applications in terms of material, quality, and geometry. Wire Arc Additive Manufacturing (WAAM) is remarkable for producing large parts in reduced times when compared to other AM methods. The possibility of producing a part with a near-net shape not only enhances productivity but also reduces resources usage. However, parts produced by WAAM may need post-processing by machining to achieve functional surface requirements. Therefore, it is important that machining, even if minimized, does not lead to a significant environmental impact. In this sense, this work evaluates the effect of using compressed air, dry cut, and synthetic biodegradable cutting fluid at varying nozzle positions and flow rates on the surface quality of ER70S-6 steel produced by WAAM, after milling with TiAlN-coated carbide tools. To analyze the surface roughness, parameters Ra, Rq, and Rz were measured and microscopy was used to further evaluate the surfaces. The surface hardness was also evaluated. The results showed that a flow rate of 10 L/min promotes better surface quality, which can be further improved using compressed air, leading to a surface quality 50% better when compared to dry cutting. Dry cut was not suitable for machining ER70S-6 WAAM material as it resulted in rough surface texture with an Rz = 4.02 µm. Compressed air was the best overall condition evaluated, achieving a 36% Ra reduction compared to dry cutting, the second-lowest hardness deviation at 6.51%, and improved sustainability by eliminating the need for cutting fluid. Full article

16 pages, 5105 KiB

Open AccessArticle

On the Effect of the Cell Size and Beam Radius on the Compressive Strength and Residual Stresses of Ti-6Al-4V BCC Lattice Sandwich Structures Manufactured by L-PBF

by Gaetano Pollara, Dina Palmeri, Roberto Licari and Antonio Barcellona

J. Manuf. Mater. Process. 2025, 9(6), 192; https://doi.org/10.3390/jmmp9060192 - 10 Jun 2025

Abstract

Lattice structures offer the possibility to obtain lightweight components with additional functionalities, improving their shock absorption and thermal exchange properties. Recently, a body-centered cubic (BCC) lattice structure has been used to fabricate metal lattice sandwich panels (MLSPs) for aerospace applications. MLSPs are made [...] Read more.

Lattice structures offer the possibility to obtain lightweight components with additional functionalities, improving their shock absorption and thermal exchange properties. Recently, a body-centered cubic (BCC) lattice structure has been used to fabricate metal lattice sandwich panels (MLSPs) for aerospace applications. MLSPs are made of two external skins and a lattice core and can be produced thanks to laser powder bed fusion technology (LPBF), which is characterized by its superior printing accuracy with respect to other additive manufacturing processes for metals. Since few studies can be found in the literature on Ti-6Al-4V MLSPs, further work is needed to evaluate the mechanical response of these panels. Moreover, due to their design complexity and to avoid a costly experimental campaign, numerical simulation could be used to encourage the industrial application of these structures. In this paper, different cell configurations were printed and tested in compression to study the influence of the cell’s geometrical parameters, i.e., the cell size and beam radius, on the mechanical response of MLSPs. Numerical simulations of the LPBF of these geometries were also carried out to understand how the residual stresses can be varied by varying the cell configuration. A geometrical evaluation was carried out to quantitatively express the influence of the beam radius and cell size on the resulting volume fraction, which strongly influences the mechanical behavior and residual stress profiles of MLSPs. From the analysis, we found that the C2-R0.35 sample resulted in the configuration with the highest compressive strength, while C3-R0.25 showed the lowest and most uniform residual stress profile. Full article

(This article belongs to the Special Issue Advanced Welding Processes, Additive Manufacturing and Numerical Models: 2nd Edition)

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21 pages, 3633 KiB

Open AccessArticle

Enhancing Mechanical Properties of Hemp and Sisal Fiber-Reinforced Composites Through Alkali and Fungal Treatments for Sustainable Applications

by Rahul Kovuru and Jens Schuster

J. Manuf. Mater. Process. 2025, 9(6), 191; https://doi.org/10.3390/jmmp9060191 - 10 Jun 2025

Abstract

The growing demand for sustainable materials has driven interest in natural fiber-reinforced composites as eco-friendly alternatives to synthetic materials. This research investigates the fabrication and mechanical performance of hemp and sisal fiber-reinforced composites, with a focus on improving fiber–matrix bonding through alkali and [...] Read more.

The growing demand for sustainable materials has driven interest in natural fiber-reinforced composites as eco-friendly alternatives to synthetic materials. This research investigates the fabrication and mechanical performance of hemp and sisal fiber-reinforced composites, with a focus on improving fiber–matrix bonding through alkali and fungal treatments. Experimental results show that fungal treatment significantly improves tensile and flexural strength, while hardness slightly decreases. Water absorption tests revealed moderate reductions in hydrophilicity compared to untreated samples, although absolute water uptake remains higher than conventional glass/epoxy composites. Microscopy analysis further confirmed enhanced fiber adhesion and structural integrity in treated specimens. These findings suggest that hybrid composites reinforced with hemp and sisal, particularly with fungal treatment, hold promise for low-to-medium load sustainable applications in the automotive interiors, packaging, and construction industries, where moderate mechanical performance and partial biodegradability are acceptable. This research contributes to the advancement of bio-based composite materials while acknowledging current limitations in long-term durability and complete biodegradability. Full article

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19 pages, 6070 KiB

Open AccessArticle

Effect of Pulsating Motion Conditions on Relubrication Behavior and Dimensions of Laterally Extruded Internal Gears

by Alireza Soleymanipoor and Tomoyoshi Maeno

J. Manuf. Mater. Process. 2025, 9(6), 190; https://doi.org/10.3390/jmmp9060190 - 10 Jun 2025

Abstract

An environmentally friendly alternative to phosphate-based lubrication was studied through the lateral cold extrusion forging of internal gears using pulsating motion. A die set with a removable punch enabled a detailed observation of relubrication, forming load, material flow, and gear geometry. Pulsating motion [...] Read more.

An environmentally friendly alternative to phosphate-based lubrication was studied through the lateral cold extrusion forging of internal gears using pulsating motion. A die set with a removable punch enabled a detailed observation of relubrication, forming load, material flow, and gear geometry. Pulsating motion with liquid lubricant significantly reduced the forming load during punch penetration, while no such effect was observed under dry conditions. Even when the number of pulses (n) was set to 1, relubrication occurred, and a comparable load reduction to that of n = 3 was achieved, shortening the forming time. When n = 3, pulsating motion contributed to increased gear height and reduced separated burr formation; however, it also caused slightly incomplete tooth filling, which may be undesirable for precision applications. Varying the pulse start position from 5.50 mm to 13.30 mm influenced forming load and material flow, further affecting gear geometry. During punch extraction, the presence of liquid lubricant reduced the load and suppressed material displacement, while dry conditions led to higher extraction loads and more deformation. Full article

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29 pages, 3463 KiB

Open AccessArticle

A Comparative Study of Mathematical Methods for Determining Colding’s Constants for Milling of Steels and Experimental Validation

by Sujan Khadka, Rizwan Abdul Rahman Rashid, John H. Navarro-Devia, Angelo Papageorgiou, Guy Stephens, Sören Hägglund and Suresh Palanisamy

J. Manuf. Mater. Process. 2025, 9(6), 189; https://doi.org/10.3390/jmmp9060189 - 9 Jun 2025

Abstract

The optimization of cutting parameters is critical for improving machining efficiency and extending tool life. Colding’s equation is one such tool life prediction equation that can be used to optimize the machining parameters. However, the equation is complex and is often challenging to [...] Read more.

The optimization of cutting parameters is critical for improving machining efficiency and extending tool life. Colding’s equation is one such tool life prediction equation that can be used to optimize the machining parameters. However, the equation is complex and is often challenging to solve to evaluate its mathematical constants. This study investigates three distinct approaches for calculating the five constants (‘K’, ‘H’, ‘M’, ‘N0’, and ‘L’) in Colding’s equation. These techniques include analytical equation calculation and different curve fitting approaches. The primary objective was to assess the accuracy and effectiveness of these methods in predicting cutting parameters. Two workpiece materials, K1045 and Mild Steel, were used with results indicating that the Python 3.13 programming approach outperformed the other methods, including MATLAB R2024b and analytical calculations, achieving error percentages of 9.08% for K1045 and 5.51% for Mild Steel compared to 12.3% and 35.3% for K1045 and 12.4% and 64.3% for Mild Steel, respectively. Furthermore, the constants ‘N0’, ‘M’, and ‘H’ displayed different values for the two materials, indicating their dependence on workpiece material properties. Moreover, it was evident that Mild Steel exhibited better machinability than K1045 at low MRR (40–80 cm³/min), with up to 55.8% longer tool life, but K1045 performed better at medium and high MRRs, suggesting different machinability behaviours under varying cutting conditions. Overall, the findings demonstrate that Colding’s model, when applied with the appropriate computational method, can accurately optimize cutting parameters for different materials, contributing to more efficient and cost-effective machining processes. Full article

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25 pages, 6526 KiB

Open AccessArticle

Engineering Perfection in GTAW Welding: Taguchi-Optimized Root Height Reduction for SS316L Pipe Joints

by Mohammad Sohel, Vishal S. Sharma and Aravinthan Arumugam

J. Manuf. Mater. Process. 2025, 9(6), 188; https://doi.org/10.3390/jmmp9060188 - 6 Jun 2025

Viewed by 174

Abstract

This study presents a systematic optimization of GTAW welding parameters to achieve a pipe-to-pipe butt weld with a root height consistently below 2 mm when joining stainless-steel 316L material, employing the Taguchi design of experiments. To the authors’ knowledge, no similar studies have [...] Read more.

This study presents a systematic optimization of GTAW welding parameters to achieve a pipe-to-pipe butt weld with a root height consistently below 2 mm when joining stainless-steel 316L material, employing the Taguchi design of experiments. To the authors’ knowledge, no similar studies have been conducted to explore the optimization of welding parameters specifically aimed at minimizing weld root height under 2 mm in stainless-steel EO pipeline welding applications. This gap in the existing literature highlights the innovative aspect of the current study, which seeks to address these challenges and improve welding precision and joint reliability. Root height, also referred to as weld root reinforcement, is defined as the excess weld metal protruding beyond the inner surface root side of a butt-welded joint. The input parameters considered are the welding current, voltage, speed, and root gap configurations of 1, 1.5, and 2 mm. Welding was performed according to the Taguchi L-09 experimental design. Nine weld samples were evaluated using liquid penetrant testing to detect surface-breaking defects, such as porosity, laps, and cracks; X-ray radiography to identify internal defects; and profile radiography to assess erosion, corrosion, and root height. Among the nine welded plate samples, the optimal root height (less than 2 mm) was selected and further validated through the welding of a one-pipe sample. An additional macro examination was conducted to confirm the root height and assess the overall root weld integrity and quality. Full article

(This article belongs to the Special Issue Innovative Approaches in Metal Forming and Joining Technologies)

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26 pages, 6653 KiB

Open AccessArticle

Investigation of the Effect of Tool Rotation Rate in EDM Drilling of Ultrafine Grain Tungsten Carbide Using Predictive Machine Learning

by Sai Dutta Gattu, Lucas Pardo Bernardi and Jiwang Yan

J. Manuf. Mater. Process. 2025, 9(6), 187; https://doi.org/10.3390/jmmp9060187 - 4 Jun 2025

Viewed by 271

Abstract

Electric discharge machining (EDM) is widely employed for machining hard, conductive materials. Tool rotation has emerged as an effective strategy to enhance debris flushing and improve stability during deep-hole EDM drilling. This study proposes a machine learning-based approach to evaluate the influence of [...] Read more.

Electric discharge machining (EDM) is widely employed for machining hard, conductive materials. Tool rotation has emerged as an effective strategy to enhance debris flushing and improve stability during deep-hole EDM drilling. This study proposes a machine learning-based approach to evaluate the influence of tool rotation and predict the unstable machining conditions in EDM of ultrafine grained tungsten carbide. A structured analytical workflow, combining Taguchi–Grey optimization, regression analysis, and classification models, was designed to capture discharge dynamics across macro- and micro-timescales. Classification models trained on raw and processed electrical signal features achieved over 88% accuracy and 90% recall. SHAP analysis revealed that the relationship between key discharge events such as sparks and short circuits varied significantly across stable and unstable machining phases, underscoring the importance of phase-specific modeling. While correlation analysis showed weak global associations, phase-dependent SHAP values revealed opposing feature effects, allowing the context-informed interpretation of model behavior. Phase segmentation revealed that, compared to 1000 RPM, short circuits were reduced by about 40% during stable machining at 8000–9000 RPM. Conversely, during unstable phases, spark effectiveness dropped by nearly 45%, and secondary discharges increased throughout this range. These insights support the design of adaptive control strategies that adjust the rotation rate in response to detected phase changes, aiming to sustain machining stability. The findings support the development of dynamic control frameworks to improve EDM performance, particularly for mold fabrication using tungsten carbide. Full article

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42 pages, 3247 KiB

Open AccessReview

Processing, Microstructure, and Mechanical Behavior of Tungsten Heavy Alloys for Kinetic Energy Penetrators: A Critical Review

by Rajneesh Patel, Gangaraju Manogna Karthik and Pawan Sharma

J. Manuf. Mater. Process. 2025, 9(6), 186; https://doi.org/10.3390/jmmp9060186 - 4 Jun 2025

Viewed by 401

Abstract

Tungsten heavy alloys (WHAs) are two-phase composites known for their exceptional density, strength, hardness, and ductility, making them ideal for radiation shielding, kinetic energy penetrators, and aerospace components. Due to their high melting point, WHAs are primarily processed via powder metallurgy, with liquid-phase [...] Read more.

Tungsten heavy alloys (WHAs) are two-phase composites known for their exceptional density, strength, hardness, and ductility, making them ideal for radiation shielding, kinetic energy penetrators, and aerospace components. Due to their high melting point, WHAs are primarily processed via powder metallurgy, with liquid-phase sintering (LPS). Spark plasma sintering (SPS) and microwave sintering are emerging as advanced consolidation techniques. Recent research has focused on improving WHA performance through microstructural manipulation, alloying with elements like Fe, Co, Mo, and Re; rare earth oxides like Y₂O₃, La₂O₃, and Ce₂O₃; and employing high-entropy alloys (HEAs) as matrix phase. Additionally, additive manufacturing (AM) techniques are increasingly being used to fabricate complex WHA components. Despite their advantages, WHAs still exhibit limitations in penetration performance, primarily due to their tendency to form mushroom-like heads upon impact rather than self-sharpening. Ongoing research seeks to enhance shear localization, refine grain structure, and optimize processing methods to improve the mechanical properties and impact resistance of WHAs. Furthermore, modeling and simulation approaches are being explored to understand the mechanical behavior of WHAs. This review comprehensively overviews the above aspects and presents recent advances in WHA processing. Full article

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16 pages, 4220 KiB

Open AccessArticle

Predicting the Relative Density of Stainless Steel and Aluminum Alloys Manufactured by L-PBF Using Machine Learning

by José Luis Mullo, Iván La Fé-Perdomo, Jorge Ramos-Grez, Ángel F. Moreira Romero, Alejandra Ramírez-Albán, Mélany Yarad-Jácome and Germán Omar Barrionuevo

J. Manuf. Mater. Process. 2025, 9(6), 185; https://doi.org/10.3390/jmmp9060185 - 3 Jun 2025

Viewed by 434

Abstract

Metal additive manufacturing is a disruptive technology that is changing how various alloys are processed. Although this technology has several advantages over conventional manufacturing, it is still necessary to standardize its properties, which are dependent on the relative density (RD). In addition, since [...] Read more.

Metal additive manufacturing is a disruptive technology that is changing how various alloys are processed. Although this technology has several advantages over conventional manufacturing, it is still necessary to standardize its properties, which are dependent on the relative density (RD). In addition, since experimental designs are costly, one solution is using machine learning algorithms that allow the effects of variations in the processing parameters on the resulting density of the additively manufactured components to be anticipated. This work assembled a database based on data from 673 observations and 10 predictors to forecast the relative density of 316L stainless steel and AlSi10Mg components produced by laser powder bed fusion (L-PBF). LazyPredict was employed to select the algorithm that best models the variability of the inherent data. Ensemble boosting regressors offer higher accuracy, providing hyperparameter fitting and optimization advantages. The predictions’ precision for aluminum and stainless steel obtained an R² value greater than 0.86 and 0.83, respectively. The results of the SHAP values indicated that laser power and energy density are the parameters that have the greatest impact on the predictability of the relative density of Al-Si10-Mg and SS 316L materials processed by L-PBF. This study presents a compendium of data for the additive fabrication of stainless steel and aluminum alloys, offering researchers a guide to understanding how processing parameters influence RD. Full article

(This article belongs to the Special Issue AI in Laser Materials Processing)

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18 pages, 7058 KiB

Open AccessArticle

In-Depth Thermal Analysis of Different Pin Configurations in Friction Stir Spot Welding of Similar and Dissimilar Alloys

by Sajad N. Alasdi and Raheem Al-Sabur

J. Manuf. Mater. Process. 2025, 9(6), 184; https://doi.org/10.3390/jmmp9060184 - 1 Jun 2025

Viewed by 328

Abstract

Over the past decade, friction stir spot welding (FSSW) has gained increasing attention, making it a competitor to conventional welding methods such as resistance welding, rivets, and screws. This type of welding is environmentally friendly because it does not require welding tools and [...] Read more.

Over the past decade, friction stir spot welding (FSSW) has gained increasing attention, making it a competitor to conventional welding methods such as resistance welding, rivets, and screws. This type of welding is environmentally friendly because it does not require welding tools and is solid-state welding. This study attempts to demonstrate the importance of pin geometry on temperature distribution and joint quality by using threaded and non-threaded pins for similar and dissimilar alloys. To this end, thermal analysis of the welded joints was conducted using real-time monitoring from a thermal camera and an infrared thermometer, in addition to finite element method (FEM) simulations. The thermal analysis showed that the generated temperatures were higher in dissimilar alloys (Al-Cu) than in similar ones (Al-Al), reaching about 350 °C. In addition, dissimilar alloys show more pronounced FSSW stages through extended periods for each plunging, dwelling, and drawing-out time. The FEM simulation results are consistent with those obtained from thermal imaging cameras and infrared thermometers. The dwelling time was influential, as the higher it was, the more heat was generated, which could be close to the melting point, especially in aluminum alloys. This study provides an in-depth experimental and numerical investigation of temperature distribution throughout the welding cycle, utilizing different pin geometries for both similar and dissimilar non-ferrous alloy joints, offering valuable insights for advanced industrial welding applications. Full article

(This article belongs to the Special Issue Recent Developments in Friction Stir Welding Technology and Applications)

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50 pages, 6501 KiB

Open AccessReview

A State-of-the-Art Review on Micro-Machining of Nitinol Shape Memory Alloys and Optimization of Process Variables Considering the Future Trends of Research

by Souradeep Dutta, Deba Kumar Sarma, Jay Vora, Rakesh Chaudhari, Abhijit Bhowmik, Priyaranjan Samal and Sakshum Khanna

J. Manuf. Mater. Process. 2025, 9(6), 183; https://doi.org/10.3390/jmmp9060183 - 30 May 2025

Viewed by 381

Abstract

The miniaturization of smart materials has become a new trend in the modern manufacturing industry due to its enormous application in the aerospace, biomedical, and automobile sectors. Nickel–titanium (NiTi)-based binary shape memory alloys (SMAs) are one of the smart materials with certain supreme [...] Read more.

The miniaturization of smart materials has become a new trend in the modern manufacturing industry due to its enormous application in the aerospace, biomedical, and automobile sectors. Nickel–titanium (NiTi)-based binary shape memory alloys (SMAs) are one of the smart materials with certain supreme features like shape memory effect, pseudo-elasticity, high ductility, strong corrosion-resistance, and elevated wear resistance. For this, several micro-machining processes have been developed to machine NiTi SMAs. This paper summarizes all of the conventional and non-conventional micro-machining processes employed to machine NiTi SMAs. In this review process, the surface integrity, dimensional accuracy of the machined surface, cutting force and tool wear analysis during conventional and non-conventional micro-machining of NiTi SMA are evaluated mostly with the aid of input process variables like cutting speed, depth of cut, width of cut, types of coolants, tool coating, discharge voltage, capacitance, laser fluence, pulse duration, scan speed, electrolysis concentration and gap voltage. The optimization of process parameters using different methods during conventional and non-conventional micro-machining of NiTi SMAs is also analyzed. The problems faced during conventional micro-machining of NiTi SMAs are overcome by non-conventional micro-machining processes as discussed. The present study aims to recognize potential developments in the improvement of the micro-machinability of NiTi SMAs. Full article

(This article belongs to the Special Issue Advances in High-Performance Machining Operations)

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29 pages, 12630 KiB

Open AccessArticle

LPBF-Produced Elastomeric Lattice Structures for Personal Protection Equipment: Mechanical Performance Versus Comfort-Related Attributes

by William Turnier Trottier, Antoine Collin, Thierry Krick and Vladimir Brailovski

J. Manuf. Mater. Process. 2025, 9(6), 182; https://doi.org/10.3390/jmmp9060182 - 29 May 2025

Viewed by 711

Abstract

This study focuses on the energy absorption and wearer comfort attributes of regular lattice structures fabricated by laser powder bed fusion from two elastomeric materials, namely TPU1301 and TPE300, for use in personal protective equipment (PPE). This study compares Body-Centered Cubic (BCC), Face-Centered [...] Read more.

This study focuses on the energy absorption and wearer comfort attributes of regular lattice structures fabricated by laser powder bed fusion from two elastomeric materials, namely TPU1301 and TPE300, for use in personal protective equipment (PPE). This study compares Body-Centered Cubic (BCC), Face-Centered Cubic (FCC) and Kelvin (KE) lattice structures with density varying from 0.15 to 0.25 g/cm³, cell size varying from 10 to 14 mm and feature size varying from 1 to 3 mm. Quasi-static and dynamic compression testing confirmed that among the studied geometries, KE structures printed with TPE300 powders provide the best combination of reduced peak acceleration and increased compliance, thereby improving both safety and comfort. Using the protection–comfort maps built on the basis of this study enables the design of lightweight and compact protective structures. For example, if a safety layer protecting a 100 mm² surface area can be manufactured from either TPE300 or TPU1100 powders using either KE or FCC structures, the KE TPE300 layer will be 1.5 times thinner and 2.5 times lighter than its FCC TPU1301 equivalent. The results of this study thus provide a basis for the optimization of lattice structures in 3D-printed PPE to meet both service and manufacturing requirements. Full article

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21 pages, 8909 KiB

Open AccessArticle

A Methodology for Acceleration Signals Segmentation During Forming Regular Reliefs Patterns on Planar Surfaces by Ball Burnishing Operation

by Stoyan Dimitrov Slavov and Georgi Venelinov Valchev

J. Manuf. Mater. Process. 2025, 9(6), 181; https://doi.org/10.3390/jmmp9060181 - 29 May 2025

Viewed by 334

Abstract

In the present study, an approach for determining the different states of ball burnishing (BB) operations aimed at forming regular reliefs’ patterns on planar surfaces is introduced. The methodology involves acquiring multi-axis accelerometer data from CNC-driven milling machine to capture the dynamics of [...] Read more.

In the present study, an approach for determining the different states of ball burnishing (BB) operations aimed at forming regular reliefs’ patterns on planar surfaces is introduced. The methodology involves acquiring multi-axis accelerometer data from CNC-driven milling machine to capture the dynamics of the BB tool and workpiece, mounted on the machine table. Following data acquisition from an AISI 304 stainless steel workpiece, which is subjected to BB treatments at different toolpaths and feed rates, the recorded signals are preprocessed through noise reduction techniques, DC component removal, and outlier correction. The refined data are then transformed using a root mean square (RMS) operation to simplify further analysis. A Gaussian Mixture Model (GMM) is subsequently employed to decompose the compressed RMS signal into distinct components corresponding to various operational states during BB. The experimental trials at feed rates of 500 and 1000 mm/min reveal that increased feed rates enhance the distinguishability of these states, thus leading to an augmented number of statistically significant components. The results obtained from the proposed GMM based algorithm applied on compressed RMS accelerations signals is compared with two other methods, i.e., Short-Time Fourier Transforms and Continuous Wavelet Transform. The results from the comparison show that the proposed GMM method has the advantage of segmenting three to five different states of the BB-process from nonstationary accelerations signals measured, while the other tested methods are capable only to distinguish the state of work of the deforming tool and state of its rapid (re-)positioning between the areas of working, when there is no contact between the BB-tool and workpiece. Full article

(This article belongs to the Topic Advanced Manufacturing and Surface Technology, 2nd Edition)

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10 pages, 1167 KiB

Open AccessArticle

Investigation of UV Picosecond Laser Damage Threshold of Anti-Reflection Coated Windows

by Priyadarshani Narayanasamy, Martin Mydlář, Hana Turčičová, Mihai George Mureșan, Ondřej Novák, Jan Vanda and Jan Brajer

J. Manuf. Mater. Process. 2025, 9(6), 180; https://doi.org/10.3390/jmmp9060180 - 29 May 2025

Viewed by 281

Abstract

Long-term stability and laser-induced damage resistance of optical components in the UV region are critical for enhancing their performance in UV high-power laser applications. This study evaluates the laser-induced damage threshold (LIDT) of commercially available UV optical windows with anti-reflective (AR) coating, produced [...] Read more.

Long-term stability and laser-induced damage resistance of optical components in the UV region are critical for enhancing their performance in UV high-power laser applications. This study evaluates the laser-induced damage threshold (LIDT) of commercially available UV optical windows with anti-reflective (AR) coating, produced through various coating techniques and designed for high-power lasers. A third-harmonic (343 nm) wavelength with good beam quality was generated in the picosecond regime to investigate the LIDT of optical components. The LIDT for each sample was measured under controlled conditions and compared based on their coating techniques. The sample coated with Al₂O₃/SiO₂ through ion beam sputtering has the best LIDT value, of 0.6 J/cm², among the tested samples, based on the hundred-thousand-pulses methodology. The damage threshold curve and the corresponding damage morphology are discussed in detail, and these findings provide insights into the durability and susceptibility of UV optics for advanced laser systems available in the market. Full article

(This article belongs to the Special Issue Advances in Laser-Based Approaches in Materials Processing and Additive Manufacturing)

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13 pages, 4178 KiB

Open AccessArticle

Evaluation of Conditions for Self-Healing of Additively Manufactured Polymer Composites with Continuous Carbon Fiber Reinforcement

by Marius Rimašauskas, Tomas Kuncius, Rūta Rimašauskienė and Tomas Simokaitis

J. Manuf. Mater. Process. 2025, 9(6), 179; https://doi.org/10.3390/jmmp9060179 - 28 May 2025

Viewed by 296

Abstract

Additive manufacturing (AM) is one of the most frequently used technologies to produce complex configuration products. Moreover, AM is very well known as a technology which is characterized by a low amount of generated waste and the potential to be called zero-waste technology. [...] Read more.

Additive manufacturing (AM) is one of the most frequently used technologies to produce complex configuration products. Moreover, AM is very well known as a technology which is characterized by a low amount of generated waste and the potential to be called zero-waste technology. As is known, there are seven main groups of technologies described in the ISO/ASTM 52900 standard that allow the use of very different materials from polymers to metals, ceramics, and composites. However, the increased utilization of additively manufactured composites for different applications requires a deeper analysis of production processes and materials’ characteristics. Various AM technologies can be used to produce complex composite structures reinforced with short fibers; however, only material extrusion (MEX)-based technology is used for the production of composites reinforced with continuous fibers (CFs). At this time, five different methods exist to produce CF-reinforced composite structures. This study focuses on co-extrusion with the towpreg method. Because of the complexity and layer-by-layer nature of the process, defects can occur during production, such as poor interlayer adhesion, increased porosity, insufficient impregnation, and others. To eliminate or minimize defects’ influence on mechanical properties and structural integrity of additively manufactured structures, a hypothesis was proposed involving heat treatment. Carbon fiber’s conductive properties can be used to heal the composite structures, by heating them up through the application of electric current. In this research article, an experimental evaluation of conditions for additively manufactured composites with continuous carbon fiber reinforcement for self-healing processes is presented. Mechanical testing was conducted to check the influence of heat treatment on the flexural properties of the composite samples. Full article

(This article belongs to the Special Issue Innovative and Sustainable Advances in Polymer Composites for Additive Manufacturing: Processing, Microstructure, Machining, and Mechanical Properties)

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23 pages, 4160 KiB

Open AccessArticle

Computed Tomography-Based Volumetric Additive Manufacturing: Development of a Model Based on Resin Properties and Part Size Interrelationship—Part I

by Amir H. Behravesh, Asra Tariq, John Buni and Ghaus Rizvi

J. Manuf. Mater. Process. 2025, 9(6), 178; https://doi.org/10.3390/jmmp9060178 - 28 May 2025

Viewed by 263

Abstract

This study presents an analytical description of the computed tomography-based volumetric additive manufacturing (VAM) process, with an emphasis on the impact of resin properties on product dimensions. The main issue addressed in this study is the assessment of the dimensional limitation of the [...] Read more.

This study presents an analytical description of the computed tomography-based volumetric additive manufacturing (VAM) process, with an emphasis on the impact of resin properties on product dimensions. The main issue addressed in this study is the assessment of the dimensional limitation of the objects produced using the VAM process, which is usually reported to be of the order of one centimeter. An analytical model is introduced to predict the product size based on the resin property (penetration depth—D_p), vial size (radius), and the duration of part formation, and the results indicate significant correlations among these parameters. A method of D_p measurement and analysis that is appropriate for the VAM process is also introduced. Mathematical justification is provided along with experimental verification for the effects of the main governing factor, D_p, on the maximum possible product size. Multiple criteria are also introduced for selecting the appropriate size of the resin container (vial) based on the desired object size and the value of D_p. It was found that the D_p is a crucial factor in analysis and experimentation in the VAM process, and its value is fundamentally different from the one obtained in the conventional polymerization AM methods. The product dimension based on the resin property, vial size, and time for the formation of the part is introduced by the analytical model. This model provides valuable insights into the complex interplay of factors influencing VAM outcomes and can facilitate informed decision-making in material selection and process design. Full article

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17 pages, 5744 KiB

Open AccessArticle

Evaluation of Mechanical Characteristics of Tungsten Inert Gas (TIG) Welded Butt Joint of Inconel 600

by Arash Moradi, Fatemeh Marashi Najafi, Yong Chen and Mahmoud Chizari

J. Manuf. Mater. Process. 2025, 9(6), 177; https://doi.org/10.3390/jmmp9060177 - 28 May 2025

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Abstract

Inconel 600 alloy has gained consideration as a favourable material for heat and power applications, particularly in turbine blades, due to its superior mechanical behaviour encompassing strength, toughness, oxidation resistance, and ductility. Tungsten Inert Gas (TIG) welding is one of the preferred techniques [...] Read more.

Inconel 600 alloy has gained consideration as a favourable material for heat and power applications, particularly in turbine blades, due to its superior mechanical behaviour encompassing strength, toughness, oxidation resistance, and ductility. Tungsten Inert Gas (TIG) welding is one of the preferred techniques for joining these alloys. Therefore, the investigation of the mechanical behaviour after the welding process is crucial for selecting the appropriate technique for joining Inconel 600 sheets. This research focuses on investigating the microstructure and mechanical behaviour of TIG-welded Inconel 600 through a series of tests, such as tensile, fatigue, creep, and hardness evaluations. In addition, microstructural analysis is combined with these mechanical evaluations to simulate the operating conditions experienced by turbine blades. Key parameters such as yield strength, tensile strength, and elongation have been evaluated through these analyses. The Ramberg–Osgood relationship has been investigated using the engineering and true stress–strain curves obtained from the welded specimens. The results of the fatigue test illustrate the relationship between strain amplitude and the number of cycles to failure for single and double-edge notched specimens. The test was performed at two different loads including 400 MPa and 250 MPa at a constant temperature of 650 °C, and the corresponding strain-time curves were recorded. The results showed rapid creep failure at 650 °C, suggesting that TIG welding may need to be optimized for high temperature applications. Full article

(This article belongs to the Special Issue Green Heat Transfer: Towards Sustainable Manufacturing of Advanced Thermal Technologies)

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12 pages, 2553 KiB

Open AccessArticle

Investigating the Influence of Mechanical Loads on Built-Up Edge Formation Across Different Length Scales at Diamond–Transition Metal Interfaces

by Mazen S. Alghamdi, Mohammed T. Alamoudi, Rami A. Almatani and Meenakshisundaram Ravi Shankar

J. Manuf. Mater. Process. 2025, 9(6), 176; https://doi.org/10.3390/jmmp9060176 - 28 May 2025

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Abstract

Investigating failure mechanisms in cutting tools used in advanced industries like biomedical and aerospace, which operate under extreme mechanical and chemical conditions, is essential to prevent failures, optimize performance, and minimize financial losses. The diamond-turning process, operating at micrometer-length scales, forms a tightly [...] Read more.

Investigating failure mechanisms in cutting tools used in advanced industries like biomedical and aerospace, which operate under extreme mechanical and chemical conditions, is essential to prevent failures, optimize performance, and minimize financial losses. The diamond-turning process, operating at micrometer-length scales, forms a tightly bonded built-up edge (BUE). The tribochemical interactions between a single-crystal diamond and its deformed chip induce inter-diffusion and contact, rapidly degrading the cutting edge upon BUE fracture. These effects intensify at higher deformation speeds, contributing to the observed rapid wear of diamond tools during d-shell-rich metal machining in industrial settings. In this study, these interactions were studied with niobium (Nb) as the transition metal. Tribochemical effects were observed at low deformation speeds (quasistatic; <1 mm/s), where thermal effects were negligible under in situ conditions inside the FEI /SEM vacuum chamber room. The configuration of the interface region of diamond and transition metals was characterized and analyzed using focused ion beam (FIB) milling and subsequently characterized through transmission electron microscopy (TEM). The corresponding inter-diffusion was examined by elucidating the phase evolution, element concentration profiles, and microstructure evolution via high-resolution TEM/Images equipped with an TEM/EDS system for elemental characterization. Full article

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25 pages, 5712 KiB

Open AccessArticle

Polymer Recycling and Production of Hybrid Components from Polypropylene and a Thermoplastic Elastomer Using Additive Manufacturing

by Shubham G. Kirve, Jens Kruse, Daniel Hesse-Hornich, Ulrich A. Handge and Malte Stonis

J. Manuf. Mater. Process. 2025, 9(6), 175; https://doi.org/10.3390/jmmp9060175 - 27 May 2025

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Abstract

Due to the significantly increasing demand for plastic components, it has become necessary to investigate polymer recycling solutions to eliminate their adverse environmental impact. The focus of this study is to examine the feasibility of recycling polypropylene and a thermoplastic elastomer up to [...] Read more.

Due to the significantly increasing demand for plastic components, it has become necessary to investigate polymer recycling solutions to eliminate their adverse environmental impact. The focus of this study is to examine the feasibility of recycling polypropylene and a thermoplastic elastomer up to five times using additive manufacturing. This study also focuses on the production and evaluation of the quality of hybrid components based on polypropylene and thermoplastic elastomers. A thermomechanical recycling approach is used, which involves subjecting polymers to thermal and mechanical processes to obtain a usable material form after each recycling cycle. Additive manufacturing was used to produce specimens using the material in both filament and granular form. The thermal, mechanical, and rheological properties of the specimens were characterized by means of various analytical techniques, including tensile test, impact test, optical microscopy, Fourier-transform infrared spectroscopy, thermogravimetric analysis, dynamic scanning calorimetry, and rheological tests in order to study the degradation characteristics of the recycled polymers. The results generally indicate that the chosen recycling procedure causes only slight alterations in the material properties by means of thermal and rheological tests, while impacting mechanical properties and printability. Full article

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32 pages, 41844 KiB

Open AccessArticle

Surface Resistivity Correlation to Nano-Defects in Laser Powder Bed Fused Molybdenum (Mo)-Silicon Carbide (SiC) Alloys

by Andrew Mason, Larry Burggraf, Ryan Kemnitz and Nate Ellsworth

J. Manuf. Mater. Process. 2025, 9(6), 174; https://doi.org/10.3390/jmmp9060174 - 26 May 2025

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Abstract

The integration of Silicon Carbide (SiC) nanoparticles into Laser Powder Bed Fusion (LB-PBF) Molybdenum (Mo) printing represents a significant advancement in refractory metal additive manufacturing. Our investigation examined how varying SiC nanoparticle sizes affect the microstructural and electrical properties of LB-PBF-printed molybdenum components [...] Read more.

The integration of Silicon Carbide (SiC) nanoparticles into Laser Powder Bed Fusion (LB-PBF) Molybdenum (Mo) printing represents a significant advancement in refractory metal additive manufacturing. Our investigation examined how varying SiC nanoparticle sizes affect the microstructural and electrical properties of LB-PBF-printed molybdenum components while maintaining a 0.01 mass fraction of Mo. At an Linear Energy Densities (LED) of 1.8 J/mm, the addition of 80 nm SiC particles achieved a 46% reduction in porosity, while sheet resistance decreased by 6% at LED of 2.0 J/mm with 80 nm SiC particles. These performance improvements stem from several mechanisms: SiC particles serve as oxygen scavengers, facilitate secondary phase formation, and enhance laser absorption efficiency. Their dual role as sacrificial oxidizing agents and Mo disilicide phase promoters represents a novel approach to addressing microcracking and porosity in LB-PBF-printed Mo components. Through systematic investigation of particle size effects on both microscale and nanoscale properties, our findings suggest that optimized nanoparticle addition could become a universal strategy for enhancing LB-PBF processing of refractory metals, particularly in applications requiring enhanced mechanical and electrical performance. Full article

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32 pages, 6571 KiB

Open AccessArticle

Exploring the Mechanical Properties of Bioprinted Multi-Layered Polyvinyl Alcohol Cryogel for Vascular Applications

by Argyro Panieraki, Nasim Mahmoodi, Carl Anthony, Rosemary J. Dyson and Lauren E. J. Thomas-Seale

J. Manuf. Mater. Process. 2025, 9(6), 173; https://doi.org/10.3390/jmmp9060173 - 26 May 2025

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Abstract

Polyvinyl alcohol cryogels (PVA-C) are promising materials for vascular tissue engineering due to their biocompatibility, hydrophilicity, and tuneable mechanical properties. This study investigates the mechanical performance of multi-layered PVA-C constructs fabricated via sub-zero extrusion-based three-dimensional (3D) bioprinting. Samples with two, four, and six [...] Read more.

Polyvinyl alcohol cryogels (PVA-C) are promising materials for vascular tissue engineering due to their biocompatibility, hydrophilicity, and tuneable mechanical properties. This study investigates the mechanical performance of multi-layered PVA-C constructs fabricated via sub-zero extrusion-based three-dimensional (3D) bioprinting. Samples with two, four, and six alternating layers were evaluated to assess the effect of layered architecture on elastic and viscoelastic behaviour. Uniaxial tensile testing revealed that increasing the number of layers led to a moderate reduction in stiffness; for instance, at 20% strain, six-layered constructs showed a significantly lower (p < 0.05) Young’s modulus (36.7 ± 2.5 kPa) compared to two-layered ones (47.3 ± 3.1 kPa). Stress–strain curves exhibited nonlinear characteristics, better captured by quadratic (as opposed to linear) fitting, within the tested strain range (≤40%). Dynamic mechanical analysis demonstrated a frequency-independent storage modulus (E′) across 1–10 Hz, with subtle variations in viscoelastic response linked to the number of layers. Visual inspection confirmed improved print fidelity and hydration retention in thicker constructs. These findings demonstrate that a multi-layered design influences the mechanical profile of PVA-C and suggests potential for functionally graded design strategies to enhance compliance matching and mimic the biomechanics of native vessels in small-diameter vascular grafts. Full article

(This article belongs to the Special Issue Recent Advances in 3D Printing Technologies in Bioengineering with Selected Papers from the 29th Congress of the European Society of Biomechanics (ESB 2024))

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24 pages, 3719 KiB

Open AccessArticle

Evaluating Self-Produced PLA Filament for Sustainable 3D Printing: Mechanical Properties and Energy Consumption Compared to Commercial Alternatives

by Luca Fontana, Paolo Minetola, Mankirat Singh Khandpur and Alberto Giubilini

J. Manuf. Mater. Process. 2025, 9(6), 172; https://doi.org/10.3390/jmmp9060172 - 24 May 2025

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Abstract

This study investigates the feasibility of self-producing polylactic acid (PLA) filament for use in 3D printing. The filament was fabricated using a desktop single-screw extruder and evaluated against commercially available PLA in terms of mechanical properties and energy consumption. Specimens were printed at [...] Read more.

This study investigates the feasibility of self-producing polylactic acid (PLA) filament for use in 3D printing. The filament was fabricated using a desktop single-screw extruder and evaluated against commercially available PLA in terms of mechanical properties and energy consumption. Specimens were printed at two layer heights (0.2 mm and 0.3 mm) and four infill densities (25%, 50%, 75%, and 100%). The self-produced filament exhibited lower diameter precision (1.67 ± 0.21 mm), which resulted in mass variability up to three orders of magnitude higher than that of the commercial filament. Thermal analysis confirmed that the extrusion and printing process did not significantly alter the thermal properties of PLA. Mechanical testing revealed that a layer height 0.3 mm consistently yielded higher stiffness and tensile strength in all samples. When normalized by mass, the specimens printed with commercial filament demonstrated approximately double the ultimate tensile strength compared to those that used self-produced filament. The energy consumption analysis indicated that a 0.3 mm layer height improved printing efficiency, cutting specific energy consumption by approximately 50% and increasing the material deposition rate proportionally. However, the total energy required to print with self-produced filament was nearly three times higher than that for commercial filament, primarily due to material waste that stems from inconsistencies in the diameter of the filament. These findings are significant in evaluating the practicality of self-produced PLA filament, particularly in terms of mechanical performance and energy efficiency. Full article

(This article belongs to the Special Issue Advances in 3D Printing Technologies: Materials, Processes, and Applications)

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20 pages, 6898 KiB

Open AccessArticle

Reinventing the Trochoidal Toolpath Pattern by Adaptive Rounding Radius Loop Adjustments for Precision and Performance in End Milling Operations

by Santhakumar Jayakumar, Sathish Kannan, Poongavanam Ganeshkumar and U. Mohammed Iqbal

J. Manuf. Mater. Process. 2025, 9(6), 171; https://doi.org/10.3390/jmmp9060171 - 23 May 2025

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Abstract

The present work intends to assess the impact of trochoidal toolpath rounding radius loop adjustments on surface roughness, nose radius wear, and resultant cutting force during end milling of AISI D3 steel. Twenty experimental trials have been performed utilizing a face-centered central composite [...] Read more.

The present work intends to assess the impact of trochoidal toolpath rounding radius loop adjustments on surface roughness, nose radius wear, and resultant cutting force during end milling of AISI D3 steel. Twenty experimental trials have been performed utilizing a face-centered central composite design through a response surface approach. Artificial Neural Network (ANN) models were built to forecast outcomes, utilizing four distinct learning algorithms: the Batch Back Propagation Algorithm (BBP), Quick Propagation Algorithm (QP), Incremental Back Propagation Algorithm (IBP), and Levenberg–Marquardt Back Propagation Algorithm (LMBP). The efficacy of these models was evaluated using RMSE, revealing that the LMBP model yielded the lowest RMSE for surface roughness (Ra), nose radius wear, and resultant cutting force, hence demonstrating superior predictive capability within the trained dataset. Additionally, a Genetic Algorithm (GA) was employed to ascertain the optimal machining settings, revealing that the ideal parameters include a cutting speed of 85 m/min, a feed rate of 0.07 mm/tooth, and a rounding radius of 7 mm. Moreover, the detachment of the coating layer resulted in alterations to the tooltip cutting edge on the machined surface as the circular loop distance increased. The initial arc radius fluctuated by 33.82% owing to tooltip defects that alter the edge micro-geometry of machining. The measured and expected values of the surface roughness, resultant cutting force, and nose radius wear exhibited discrepancies of 6.49%, 4.26%, and 4.1%, respectively. The morphologies of the machined surfaces exhibited scratches along with laces, and side flow markings. The back surface of the chip structure appears rough and jagged due to the shearing action. Full article

(This article belongs to the Special Issue Advances in High-Performance Machining Operations)

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13 pages, 4249 KiB

Open AccessArticle

The First Layer: Single-Track Insights into Direct Energy Deposition Processed Cu-Ni Thermoelectric Alloys

by Nick Williams, Kyle Snyder, Ian Smith, Anthony Duong, Everett Carpenter and Radhika Barua

J. Manuf. Mater. Process. 2025, 9(6), 170; https://doi.org/10.3390/jmmp9060170 - 23 May 2025

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Abstract

The shift to sustainable energy has accelerated the development of thermoelectric (TE) material for direct heat-to-electricity conversion without batteries or grid reliance. Cu-Ni alloys show promise for high-power, thermally stable TE applications like waste heat recovery and electronics cooling but require thermal conductivity [...] Read more.

The shift to sustainable energy has accelerated the development of thermoelectric (TE) material for direct heat-to-electricity conversion without batteries or grid reliance. Cu-Ni alloys show promise for high-power, thermally stable TE applications like waste heat recovery and electronics cooling but require thermal conductivity and microstructure optimization. This study investigates additive manufacturing (AM) of Cu-Ni alloys via laser powder-directed energy deposition (L-DED), enabling precise control over deposition parameters. Track geometries were analyzed using linear mass density (M_L) and linear heat input (H_L), which influence deposition quality and microstructural characteristics. A weighted qualitative process parameter decision matrix was developed to evaluate process conditions systematically. Optimal deposition was achieved with H_L < 70 J/mm for M_L ~0.016–0.021 g/mm and 98 J/mm < H_L < 137 J/mm for M_L = 0.026 g/mm, corresponding to an energy-to-mass ratio of ~4000 ± 500 kJ/g. While this study does not directly assess thermoelectric properties, it provides essential first-layer insights into how processing conditions affect track geometry, defect formation, and microstructure—information that is foundational for optimizing multi-layer builds and, ultimately, improving thermoelectric performance. These findings mark a critical step toward predictive process optimization and the accelerated design of Cu-Ni-based thermoelectric materials using AM techniques. Full article

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J. Manuf. Mater. Process., Volume 9, Issue 6 (June 2025) – 24 articles

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