J. Manuf. Mater. Process., Volume 8, Issue 5 (October 2024) – 16 articles

Additive manufacturing (AM) methods have been gaining momentum because they provide vast design and fabrication possibilities, increasing the accessibility of state-of-the-art hardware through recent developments in user-friendly computer-aided drawing/engineering/manufacturing (CAD/CAE/CAM) tools. However, in comparison to the conventional manufacturing methods, AM processes have some disadvantages, including the machining precision and fabrication process times. The first issue has been mostly resolved through the recent advances in manufacturing hardware, sensors, and controller systems. However, the latter has been widely investigated by researchers with different toolpath planning perspectives. As a contribution to these investigations, the present study proposes a toolpath planning method for AM, which aims to provide highly continuous yet distance-optimized solutions. The approach is based on the utilization of the signed distance field (SDF), clustering, and minimization of toolpath distances among cluster centroids. The method was tested on various geometries with simple closed curves to complex geometries with holes, which provides effective toolpaths, e.g., with relative distance reduction percentages up to 16.5% in comparison to conventional rectilinear infill patterns. Full article

The friction/adhesion between the tool and chip is generally large in metal cutting, and it causes many problems such as high cutting energy/rough surface finish. To suppress this, cutting fluid and tool coating are used in practice, but they are high in energy/cost and environmentally unfriendly. Therefore, this paper investigates the extraordinarily high-speed cutting (EHS cutting) mechanics of mainly soft and highly heat-conductive materials and proposes their application to solve the friction/adhesion problem in an environmentally friendly manner. In order to clarify the EHS cutting mechanics, a simple analytical model is constructed and experiments are conducted with measurement of the cutting temperature and forces. As a result, the following points are clarified/found: (1) heat softening at the secondary plastic deformation zone rather than the primary plastic deformation zone, (2) friction coefficient drop to 0.170 in EHS cutting, and (3) gradually increasing trend of cutting temperature in EHS cutting. Finally, EHS cutting is applied to dry cutting of aluminum alloys with a non-coated carbide tool and compared to conventional wet cutting with a DLC-coated carbide tool, and it is shown that a coating/coolant can be omitted in this region to achieve environmentally friendly cutting. Full article

Selective laser sintering (SLS) is a bed fusion additive manufacturing technology that facilitates rapid, versatile, intricate, and cost-effective prototype production across various applications. It supports a wide array of thermoplastics, such as polyamides, ABS, polycarbonates, and nylons. However, manufacturing plastic components using SLS poses significant challenges due to issues like low strength, dimensional inaccuracies, and rough surface finishes. The operational principle of SLS involves utilizing a high-power-density laser to fuse polymer or metallic powder surfaces. This paper presents a comprehensive analysis of the SLS process, emphasizing the impact of different processing variables on material properties and the quality of fabricated parts. Additionally, the study explores the application of machine learning (ML) techniques—supervised, unsupervised, and reinforcement learning—in optimizing processes, detecting defects, and ensuring quality control within SLS. The review addresses key challenges associated with integrating ML in SLS, including data availability, model interpretability, and leveraging domain knowledge. It underscores the potential benefits of coupling ML with in situ monitoring systems and closed-loop control strategies to enable real-time adjustments and defect mitigation during manufacturing. Finally, the review outlines future research directions, advocating for collaborative efforts among researchers, industry professionals, and domain experts to unlock ML’s full potential in SLS. This review provides valuable insights and guidance for researchers in regard to 3D printing, highlighting advanced techniques and charting the course for future investigations. Full article

This experimental study was performed to assess whether applying a metal primer containing 10-MDP multiple times affected the repair shear bonding ability of base metal alloys to resin composites. Ten base metal alloys were randomly assigned to each group in the manner described, following multiple applications of a metal primer (Clearfil Ceramic Primer Plus), namely one to five applications, and no primer application as a negative control. On the specimens’ prepared surfaces, the resin composite was pushed into the mold and then light-activated for 40 s. The bonded samples were kept for 24 h at 37 °C in distilled water in an incubator. The shear bond strength was determined using a universal testing device. A stereomicroscope was used to determine the debonded surface. The one-way ANOVA and Tukey’s test were implemented to statistically analyze. The lowest shear bond strength was found in group 6 (6.14 ± 1.12 MPa), demonstrating a significant difference (p = 0.000) when compared to groups 1 to 5. The shear bond strength of group 3 was highest at 21.49 ± 1.33 MPa; there was no significant difference between group 3 and groups 4 and 5 (20.21 ± 2.08 MPa and 20.98 ± 2.69 MPa, respectively) (p = 0.773, p = 1.000, respectively). All fractured specimens in groups 1, 2, and 6 were identified as adhesive failure. Groups 3 and 4 exhibited the highest percentage of mixed failures. To achieve the repair shear bonding ability of base metal alloys to resin composites, the sandblasted base metal alloys should be coated with three applications of a metal primer before applying the adhesive agent. Full article

Plastics reinforced with glass fiber have a significant likelihood of being replaced by natural fiber hybrid composites (NFHCs). Making holes helps in part assembly, which is a crucial activity in the machining of composite constructions. As a result, choosing the right drill bit and cutting parameters is crucial to creating a precise and high-quality hole in composite materials. The present study employs the Taguchi approach to examine the delamination behavior and hole quality of ramie–bamboo composite laminates consisting of epoxy and nano-fillers (SiC, Al₂O₃) with feed, spindle speed, and three distinct drill bit types. Surface roughness and delamination are significantly influenced by feed and spindle speed, as indicated by the results of the analysis of variance. It was found that the spindle speed had a major impact on the delamination factor and surface roughness, while the feed and drill bit type had a minor influence. The surface roughness (76.5%) and delamination factor (66.7%) are significantly affected by the spindle speed. Full article

Tool wear management and real-time machining quality monitoring are pivotal components of realizing smart manufacturing objectives, as they directly influence machining precision and productivity. Traditionally, measuring and analyzing cutting force fluctuations in the time domain has been employed to diagnose tool wear effects. This study introduces a novel, indirect approach that leverages spindle-load current variations as a proxy for cutting force analysis. Compared to conventional methods relying on machining vibration or direct cutting force measurement, this technique provides a safer, simpler, and more cost-effective means of data aquisition, with reduced computational demands. Consequently, it is ideally suited for real-time monitoring and long-term analyses such as tool-life prediction and surface-roughness evolution induced by tool wear. An intelligent tool wear monitoring system was developed based on spindle-load current data. The system employs extensive cutting experiments to identify and analyze the correlation between tool wear and spindle-load current signal patterns. By establishing a tool wear near-end-of-life threshold, the system enables intelligent monitoring using C#. Experimental validation under both roughing and finishing conditions demonstrated the system’s exceptional diagnostic accuracy and reliability. The results demonstrate that the current ratio threshold value has good universality in different materials, indicating that monitoring the machining current ratio to estimate the degree of tool wear is a feasible research direction, and that the average error between the experimental surface-roughness measurement value and the predicted value was 10%. Full article

Today, around the world, there is huge demand for natural materials that are biodegradable and possess suitable properties. Natural fibers reveal distinct aspects like the combination of good mechanical and thermal properties that allow these types of materials to be used for different applications. However, fibers alone cannot meet the required expectations; design modifications and a wide variety of combinations must be synthesized and evaluated. It is of great importance to research and develop materials that are bio-degradable and widely available. The combination of PLA+, a bio-based polymer, with natural fillers like sawdust and soybean oil offers a novel way to create sustainable composites. It reduces the reliance on petrochemical-based plastics while enhancing the material’s properties using renewable resources. This study explores the creation of continuous hexagonal-shaped 3D-printed PLA+ samples and the application of post-print fillers, specifically sawdust and soybean oil. PLA+ is recognized for its eco-friendliness and low carbon footprint, and incorporating a hexagonal pattern into the 3D-printed PLA+ enhances its structural strength while maintaining its density. The addition of fillers is crucial for reducing shrinkage and improving binding capabilities, addressing some of PLA+’s inherent challenges and enhancing its load-bearing capacity and performance at elevated temperatures. Additionally, this study examines the impact of varying filler percentages and pattern orientations on the mechanical properties of the samples, which were printed with an infill design. Full article

Shot peening is generally used to improve the fatigue performance of mechanical components. However, identifying the geometrical and mechanical characteristics of the shots that improve fatigue strength is still a challenging task, as there are many variables involved in the shot peening process. The present work addresses the effect of different shot media on the fatigue behaviour of an aluminium alloy 6082 T6. Four different shot types were used: silica microspheres, alumina shots, aluminium cut wire and zinc cut wire. Axial fatigue tests were carried out to obtain the Wöhler curves corresponding to each shot peening treatment. The surface properties of the shot-peened specimens, such as grain size, hardness, residual stress and roughness were measured to determine their effect on the fatigue results. The fatigue results revealed that silica and zinc shots increased significantly the fatigue life of the alloy, whereas alumina and aluminium shots reduced its fatigue strength. Almen intensities have shown to correlate well with grain refinement and strain hardening. However, better fatigue results were obtained with the shots that generated higher surface compressive residual stresses. It is believed that small and smooth shots are preferable to sharp and irregular ones, regardless of the Almen intensity or surface hardness attained with the latter. Full article

As the metal additive manufacturing (AM) field evolves with an increasing demand for highly complex and customizable products, there is a critical need to close the gap in productivity between metal AM and traditional manufacturing (TM) processes such as continuous casting, machining, etc., designed for mass production. This paper presents the development of the scalable and expeditious additive manufacturing (SEAM) process, which hybridizes binder jet printing and stereolithography principles, and capitalizes on their advantages to improve productivity. The proposed SEAM process was applied to stainless steel 420 (SS420) and the processing conditions (green part printing, debinding, and sintering) were optimized. Finally, an SS420 turbine fabricated using these conditions successfully reached a relative density of 99.7%. The SEAM process is not only suitable for a high-volume production environment but is also capable of fabricating components with excellent accuracy and resolution. Once fully developed, the process is well-suited to bridge the productivity gap between metal AM and TM processes, making it an attractive candidate for further development and future commercialization as a feasible solution to high-volume production AM. Full article

The chip compression ratio is the most important characteristic of various machining processes with chip generation. This characteristic enables the determination of kinetic and other energy loads on the tool and the machined material. This provides an overall evaluation of the machining process and the possibility of its subsequent optimization. This paper presents the results of determining this cutting characteristic by experimental method, analytical calculation, and numerical modeling. For the analytical calculation of the chip compression ratio, an analytical cutting model developed based on the variational principle of the minimum potential energy was used. A finite element model of orthogonal cutting was used for the numerical simulation of the above process characteristic. Experimentally, the chip compression ratio was determined by the ratio of the chip thickness to the cutting depth (undeformed cutting thickness). The chip thickness was determined by direct measurement using chip slices obtained during the cutting process. The Johnson–Cook constitutive equation was used as the machined material model and the Coulomb model was used as the friction model. The generalized parameters’ determination of the constitutive equation was performed through a DOE (Design of Experiment) sensitivity analysis. The variation range of these parameters was chosen based on the analysis of the effect of individual parameters of the constitutive equation on the chip compression ratio value. The largest deviations between the experimental and analytically calculated values of the chip compression ratio did not exceed 21%. At the same time, the largest deviations of simulated values of the indicated cutting characteristic and its experimental values did not exceed 20%. When comparing the experimental values of the chip compression ratio with the corresponding calculated and simulated values, the deviations were within 22%. Full article

The massive forming industry in Germany produces around 1.4 million parts every year, which are mainly used in safety-relevant areas such as the automotive industry. The production of these parts requires a considerable amount of energy, much of which remains unused and causes high CO₂ emissions. An efficient approach to reduce these emissions and improve material utilization is cross-wedge rolling, which enables efficient material utilization but is limited by the so-called Mannesmann effect, which leads to unwanted material defects. This paper describes the development and validation of a safe design criterion for cross-wedge rolling tools in order to avoid material damage caused by the Mannesmann effect and thus increase resource efficiency in forging. Based on simulation-supported investigations and experimental tests, process maps are created for various materials. The validation is carried out both in an experimental test facility with real tools and in an industrial production facility, which leads to a significant reduction in excess material and CO₂ emissions. The results show that the full resource potential of cross-wedge rolling can be exploited by optimizing process parameters and tool geometries. Full article

Multilayer composite materials, consisting of layers of aluminum alloy and steel, are used in the manufacturing of large engineering structures, including in the shipbuilding and railcar industries. Due to the different properties of aluminum alloys and steels, it is difficult to achieve high-strength joints by conventional welding. Therefore, these joints are produced by explosive welding. In the present work, the structure of a multilayer material, AA1070-AlMg6-AA1070 (aluminum alloys)-VT1-0-08Cr18Ni10Ti (steel), was investigated after explosive welding and heat treatments were performed under different conditions. The microstructure of the AlMg6 layer at the AlMg6-AA1070 interface consists of shaped anisotropic grains extending along the weld interface. The AA1070 layer is enriched with magnesium due to its diffusive influx from AlMg6. In the AlMg6 and VT1-0 layers, adiabatic shear bands are found that start at the weld interface and propagate deep into the material. The optimal temperature for the heat treatment is 450–500 °C, as internal stresses are reduced at this temperature and the grain structure of the AlMg6 layer is not coarse. Tear strength testing revealed that the tear strength of the composite material after explosive welding was 130 ± 10 MPa, which exceeded the strength of the AA1070 alloy. Full article

The rapid spread of the use of high-density polyethylene (HDPE) pipes is due to the wide variety of methods for connecting them. This study keeps pace with the developments of butt fusion welding of HDPE pipes by exploring the relationship between the performance of the weld joints by studying ultimate tensile strength and exploring the joint welding profiles by studying the shape of the joint at the outer surface of the pipe (height and width of the joint cap) and the shape of the joint at the internal surface (height and width of the joint root). Welding pressure, heater temperature, stocking time, and cooling time were the parameters for the welding process. Regression was analyzed using ANOVA, and an ANN was used to analyze the experimental results and predict the outputs. Two optimization techniques (pattern search and genetic algorithm) were applied to obtain the ideal operating conditions and compare their performance. The results showed that pattern search and genetic algorithms can determine the optimal output results and corresponding welding parameters. In comparison between the two methods, pattern search has a limited relative advantage. The optimal values for the obtained outputs revolved around a tensile strength of 35 MPa (3.45 and 4.5 mm for the cap and root heights, and 8 and 6.98 mm for the cap and root widths, respectively). When comparing the effects of welding parameters on the results, welding pressure had the best effect on tensile strength, and plate surface temperature had the most significant effect on the welding profile geometries. Full article

In the aerospace industry, an important number of machined parts are submitted for high-performance requirements regarding surface integrity. Key components are made of materials selected for their unique properties and they are obtained by milling processes. In most situations, the milling process uses cooling methods because, in their absence, the material surface could be affected by the generated heat (temperatures could reach up to 850 °C), the residual stress, the cutting forces, and other factors that can lead to bad integrity. Cryogenic cooling has emerged as a pivotal technology in the manufacturing of aeronautical materials, offering enhanced properties and efficiency in the production process. By utilizing extremely low temperatures, typically involving liquid nitrogen or carbon dioxide, cryogenic cooling can significantly enhance the material’s properties and machining processes. Cryogenic gases are tasteless, odorless, colorless, and nontoxic, and they evaporate without affecting the workers’ health or producing residues. Thus, cryogenic cooling is also considered an environmentally friendly method. This paper presents the advantages of cryogenic cooling compared with the classic cooling systems used industrially. Improvements in terms of surface finishing, tool life, and cutting force are highlighted. Full article

The growing interest in sustainable and biodegradable materials has prompted significant attention towards natural fiber-reinforced composites (FRC) due to their lower environmental impacts. In a similar sustainable vein, this study fabricated composite materials utilizing bagasse fibers with the 3D SLA (Stereolithography) printing method. To start with, a novel fiber extraction process was adopted for extracting fiber from the bagasse stem in three distinct methods (Process-1, Process-2, and Process-3). The fiber extraction process includes washing, sun-drying, manual collection of rind fibers, immersion of rind fibers in NaOH at specific concentrations for specific durations, combing, and drying. In Process-1, the rind fibers were immersed in 5% NaOH for 15 h, while in Process-2 and Process-3, the rind fibers were immersed in 1% NaOH, but the soaking time varied: 25 h for Process-2 and 18 h for Process-3.for 25 h, and in Process-3, the rind fibers were immersed in 1% NaOH for 18 h. The resulting bagasse fibers underwent comprehensive property assessment with a focus on functional group analysis, diameter measurement, and tensile strength assessment. Subsequently, these fibers were used to fabricate composite materials via the 3D SLA printing technique after being treated in a NaOH solution. The Fourier Transform Infrared (FTIR) Spectroscopy results clearly showed that a fraction of hemicellulose and lignin was removed by NaOH, resulting in improved tensile strength of the bagasse fibers. Three-dimensional-printed composites reinforced with bagasse fibers extracted through the P1 method showed the highest improvement in tensile strength (approximately 70%) compared to specimens made from pure resin. The lack of pores in the composite and the observable fiber fracture phenomena clearly indicate that 3D printing technology effectively enhances the quality of the interface between the fiber and the matrix interfacial bonding, consequently resulting in improved tensile properties of the composites. The 3D-printed composites reinforced with bagasse fiber showcased impressive tensile properties and provided solutions to the limitations of traditional composite manufacturing methods. This sets the stage for developing innovative composite materials that combine natural fibers with cutting-edge fabrication techniques, offering a promising path to tackle present and future economic and ecological challenges. Full article

In this study, the mechanical properties of SSM-ADC12 aluminum alloy specimens with a ZnAl4Cu3 zinc alloy interlayer were observed after Transient Liquid Phase Diffusion Bonding (TLPDB), a welding process conducted in a semi-solid state. The purpose of the experiment was to study how the following parameters—bonding temperature (400, 430, 460, 490, and 520 °C), bonding time (60, 90, and 120 min), and thickness of the ZnAl4Cu3 zinc alloy (0.5, 1.0, and 2.0 mm)—affect the mechanical properties and the types of defects that formed. The results show that the bonding strength varied significantly with different parameters following the TLPDB process. A maximum bonding strength of 32.21 MPa was achieved at a bonding temperature of 490 °C, with 20 min of bonding and a ZnAl4Cu3 zinc alloy layer that was 2.0 mm thick. Conversely, changing the welding parameters influenced the bonding strength. A minimum bonding strength of 2.73 MPa was achieved at a bonding temperature of 400 °C, with a bonding time of 90 min and a ZnAl4Cu3 zinc alloy interlayer that was 2.0 mm thick. The Vickers microhardness results showed that the bonded zone had a lower hardness value compared to the base materials (BMs) of the SSM-ADC12 aluminum alloy (86.60 HV) and the ZnAl4Cu3 zinc alloy (129.37 HV). The maximum hardness was 83.27 HV, which resulted from a bonding temperature of 520 °C, a bonding time of 90 min, and a ZnAl4Cu3 zinc alloy that was 2.0 mm thick. However, in the near interface, the hardness value increased because of the formation of MgZn₂ intermetallic compounds (IMCs). The fatigue results showed that the stress amplitude was 31.21 MPa in the BMs of the SSM-ADC12 aluminum alloy and 20.92 MPa in the material that results from this TLPDB process (TLPDB Material) when the limit of cyclic loading exceeded 10⁶ cycles. Microstructural examination revealed that transformation from a β-eutectic Si IMC recrystallization structure to η(Zn–Al–Cu) and β(Al₂Mg₃Zn₃) IMCs occurred. A size reduction to a width of 6–11 µm and a length of 16–44 µm was observed via SEM. Finally, voids or porosity and bucking defects were found in this experiment. Full article