Manufacturing Process Research Articles

Sawtooth scanning strategy for additive manufacturing

Purpose This study aims to improve the acceleration in the additive manufacturing (AM) process. AM tools, such as extrusion heads, jets, electric arcs, lasers and electron beams (EB), experience negligible forces. However, their speeds are limited by the positioning systems. In addition, a thin tool must travel several kilometers in tiny motions with several turns while realizing the AM part. Hence, acceleration is a more significant limiting factor than the velocity or precision for all except EB. Design/methodology/approach The sawtooth (ST) scanning strategy presented in this paper minimizes the time by combining three motion features: zigzag scan, 45º or 135º rotation for successive layers in G00 to avoid the CNC interpolation, and modifying these movements along 45º or 135º into sawtooth to halve the turns. Findings Sawtooth effectiveness is tested using an in-house developed Sand AM (SaAM) apparatus based on the laser–powder bed fusion AM technique. For a simple rectangle layer, the sawtooth achieved a path length reduction of 0.19%–1.49% and reduced the overall time by 3.508–4.889 times, proving that sawtooth uses increased acceleration more effectively than the other three scans. The complex layer study reduced calculated time by 69.80%–139.96% and manufacturing time by 47.35%–86.85%. Sawtooth samples also exhibited less dimensional variation (0.88%) than zigzag 45° (12.94%) along the build direction. Research limitations/implications Sawtooth is limited to flying optics AM process. Originality/value Development of scanning strategy for flying optics AM process to reduce the warpage by improving the acceleration.

Effect of in situ CO2 mixing of cement paste on the leachability of hexavalent chromium (Cr(VI)).

In situ CO2 mixing technology is a potential technology for permanently sequestering CO2 during concrete manufacturing processes. Although it has been approved as a promising carbon capture and utilisation (CCU) method, its effect on the leachability of heavy metals from cementitious compounds has not yet been studied. This study focuses on the effect of in situ CO2 mixing of cement paste on the leaching of hexavalent chromium (Cr(VI)). The tank leaching test of the CO2 mixing cement specimen resulted in a Cr(VI) cumulative leaching of 0.614mg/m2 in 28 d, which is ten times lower than that of the control mixing specimens. The results in thermogravimetric analysis indicated that a relatively significant amount of CrO42- is immobilised as CaCrO4 during the CO2-mixing, and a higher Cr-O extension is observed in the Fourier transform infrared spectra. Furthermore, a portion of the monocarboaluminate is inferred from microstructural analyses to incorporate CrO42- ions. These results demonstrate that in situ CO2 mixing is beneficial not only in reducing CO2 emissions, but also in controlling the leaching of toxic substances.

Nano-microcrystals revealed on Tang dynasty gilded bronze using advanced TEM-SEM and synchrotron methods.

Over the years, numerous gold and silver artifacts have been excavated from the tombs of the Tang dynasty, which give evidence of the sophisticated metalworking techniques at that time. Few of the artifacts were thoroughly studied and their manufacturing processes were barely known. The present investigation concerns a metal headgear from a newly excavated tomb of a female in Xi'an of the Tang dynasty (618-907 A.D.), using advanced techniques in a complementary way, especially performing a detailed analysis of the corrosion products and alloying processes. The combined state-of-the-art methods and instrumentation used for the corrosion study included spectroscopy, diffraction, electron microscopy, synchrotron and their versions for specific measurements and sample preparation. The investigated headgear metal consists of a copper-based core, which is gilded by a thin gold layer, consisting of an Au-Hg alloy with a thin layer of about 400 nm. The technique used for shaping and hammered embellishments led to the creation of nanosized grains on the side that would eventually be the interior of the headgear. It was gilded using the mercury-amalgamation process, and the liquid diffusion caused the development of intermetallic compounds. This is the first recorded instance of these nano-scale and eutectic phases being observed on objects from an archaeological context. The crystallographic analysis offered valuable insights into the formation of needle-like malachite crystals growing on a layer of cuprite found on the surface of the corroded piece. The results highlight that the artisans utilized advanced methods in the creation of funerary items during the Tang dynasty.

Experimental Assessment of Hemp Shiv and Green Adhesives to Produce a Biocomposite Material

This study investigated the utilization of innovative green composites made from hemp shiv, a waste by-product of hemp cultivation, with the aim of promoting sustainability within the construction industry. The manufacturing method involved the application of pressure in a mold to create the samples. These materials were produced using an environmentally friendly binder consisting of colophony, arabic gum, and corn starch. Moreover, white glue and bioepoxy were also used to compare with the green resins. Three different binder compositions were used for the specimens. The samples underwent mechanical testing through tensile and bending assessments, and their performance was compared to that of non-green binders to validate the effectiveness of the manufacturing processes. The study revealed that decreasing the moisture content during the curing process was crucial for improving the mechanical properties. The best results were achieved when using arabic gum as a binder, yielding a tensile strength of 2.16 MPa and a bending strength of 5.25 MPa, with a composition of 62.5% hemp shiv and a manufacturing process involving a pressure of 5 MPa.

Investigation of the impact of environmental conditions on the mechanical properties of thin film copper wafers

Abstract Thin film copper offers excellent film texture for multilevel interconnections in integrated circuits fabrication because of its superior resistivity to electromigration and high electricelectrical conductivity. To perform a semiconductor fabrication of copper during chemical mechanical planarization process, it is necessary to have a thorough understanding of the nanomechanical properties of thin film copper. In this study, thin film copper and reacted passivation layers on silicon substrate wafer are investigated for their nanomechanical properties under various environmental conditions. The results of this study indicate that thin film copper passivation layers have different properties in deionized water and polishing slurry environments compared to thin film copper exposed to ambient air. The insights gained from this study emphasize the significance of considering both the passivation layers and wet environments in semiconductor fabrication processes, contributing to the advancement of copper-based interconnect materials and optimization of the chemical mechanical planarization process in semiconductor manufacturing.

Criticality of volumetric defect structure on fatigue properties of stainless steel 316L fabricated by laser powder direct energy deposition

As one of the significant metal additive manufacturing (AM) processes, laser powder direct energy deposition (LP-DED) has established its role in specific applications, including component repair, coatings, and multi-material structure. However, one of the limiting factors for the wide adoption of LP-DED is the formation of volumetric defects during the printing process. These defects are one of the crucial causes of poor and scattered mechanical properties, especially fatigue performance, by accelerating fatigue crack initiation, growth, and final failure. Unraveling defect structure-fatigue correlations can help understand how defects are affecting fatigue properties, how critical they are, and, finally, what solutions can be utilized to diminish their harmful effects. In this research study, novel defect features, including size features, shape descriptors, and location features, were proposed and investigated regarding fatigue properties in LP-DED. Accordingly, stainless steel 316L (SS 316L) blocks were fabricated by LP-DED. After cutting out the dog-bone samples by wire electric discharge machining (EDM), X-ray Computed Tomography (XCT) and subsequent fatigue tests were conducted. The defect features and their statistical descriptors were extracted from XCT data. By statistical analysis of the features, valuable insights regarding their correlations with fatigue life were realized.

Optimization of Fused Filament Fabrication for High-Performance Polylactic Acid Parts under Wear Conditions

This paper investigates the impact of various manufacturing parameters on the mechanical and tribological properties of high-performance PLA (polylactic acid) parts produced using Fused Filament Fabrication (FFF). It addresses the challenges associated with optimizing additive manufacturing processes, particularly for polymer-based materials, and emphasizes the importance of understanding how factors such as build orientation, layer thickness, and infill density influence the final properties of the printed parts. This study highlights the improvements that can be achieved by incorporating reinforcements such as carbon fibers and graphene nanoplatelets into PLA, enhancing its mechanical strength and wear resistance. Experimental results show that optimizing printing parameters can significantly reduce the coefficient of friction and wear, leading to better performance in applications involving movement and mechanical stress. Key findings include the observation that higher infill densities and specific build orientations improve the fatigue life and tensile strength of PLA parts. Additionally, post-printing thermal treatments can alleviate internal stresses and enhance interlayer adhesion, further improving mechanical properties. The article concludes that with proper optimization, high-performance PLA can be a viable material for industrial applications, offering both environmental benefits and enhanced performance.

The manufacture of natural hydraulic limes: Influence of raw materials' composition, calcination and slaking in the crystal-chemical properties of binders

This study aims to achieve an in-depth understanding of the manufacturing process of natural hydraulic lime (NHL) by assessing the influence of raw materials' chemical- mineralogical composition and the effect of the slaking process. NHLs with variable hydraulicity were manufactured using 56 raw materials from carbonate outcrops in Andalusia (Spain). This study shows that siliceous limestones with microcrystalline quartz generate hydraulic phases after calcination. However, when the amount of this reactive silica exceeds 18% by weight, CaO is not formed, and only calcium silicates appear. It was also found that slaking of NHL leads to partial hydration of the most reactive calcium silicates, reducing the expected reactivity of the lime. Instead, exposure of NHL quicklimes to environmental relative humidity promotes the formation of disordered portlandite and reduces the partial hydration of hydraulic phases. Our findings demonstrate that standard slaking can be replaced by alternative methods for the studied binders.

Development of a Sustainable Polymer Composite: Enhancing Properties of Waste Plastic with Ground Tire Rubber Reinforcement

Abstract The growing interest in utilizing waste for composite development has prompted investigations across social, economic, and environmental domains. This study focuses on utilizing recyclable waste plastic materials and micro-sized ground tire rubber (GTR) of varying sizes (600 µm, 300 µm, and 150 µm) to create a polymer matrix composite (PMC). Employing a thermal blending technique, the manufacturing process adjusts the composition ratios of polymer and GTR from 90:10 to 50:50. Subsequently, Energy Dispersive Spectroscopy (EDS) is utilized to analyze the PMC composition, while Fourier-transform infrared spectroscopy confirms functional group and chemical structure. The study demonstrates significant improvements in various properties upon adding GTR to High-Density Polyethylene (HDPE) and Low-Density Polyethylene (LDPE) composite materials. For HDPE-GTR composites, the melting temperature (Tm) ranged from 120.29°C to 138.53°C, crystallization temperature (Tc) from 102.84°C to 127.14°C, and enthalpy of melting (ΔHm) from 70.96 to 139.67 J/g. Crystallinity (Xc) varied from 48.43% to 52.96%. In LDPE-GTR composites, Tm ranged from 106.08°C to 129.57°C, Tc from 90.27°C to 112.20°C, ΔHm from 75.59 to 142.53 J/g, and Xc from 51.59% to 54.05%. Moreover, mechanical properties such as tensile strength, flexural modulus, and impact strength exhibited enhancements with GTR addition to the polymer matrix. These findings underscore the potential of sustainable waste utilization, advancing environmentally friendly and resource-efficient composite materials.

Coordinate system setting for post-machining of impeller shape by wire arc DED and evaluation of processing efficiency

Wire arc additive manufacturing (WAAM) is a direct energy deposition (DED) process that uses arc welding. It is a method of stacking beads made by melting metal wires with an arc heat source generated by a short-circuit current. Compared to other metal additive manufacturing methods, this process can be used to quickly produce large and complex-shaped metal parts. However, due to the multi-bead stacking method, the surface is highly curved and the dimensional errors are large; therefore, post-processing of the surface by cutting is required. Impellers, which are widely used in various industries, have complex shapes and high material consumption during cutting; therefore, the WAAM process can improve the manufacturing efficiency. In this study, a manufacturing process for an impeller with a diameter of 160 mm was developed by using the WAAM process. A 6-bladed fan-type impeller used for high-pressure fluid delivery was similarly modeled, and the product was additively manufactured using an Inconel 625 alloy wire. Manufacturing conditions that ensure productivity and quality or the product were determined through experimentation. Considering the post-processing of the WAAM-fabricated structure, the robot and tool paths of the impeller model were designed, and the error in the process coordinate system caused by attaching and detaching the workpiece between the two processes was reduced. Through the post-processing of the WAAM-fabricated structure, the production efficiency and process reliability were verified when the conventional manufacturing method and WAAM process were applied.

Prevalence and Characterization of Salmonella during Pork Sausage Manufacturing

Pork carcasses and meat may harbor Salmonella and may contaminate other products during harvest and fabrication. Sources of contamination include manure on hides, environmental contamination, ingredients from external sources, and lymph nodes. Swine lymph nodes are often incorporated into ground meat, as their anatomical location makes removal labor prohibitive. A sausage processing plant in the midwestern United States was sampled monthly (except for December) from May 2021 to April 2022 to enumerate Salmonella and Enterobacteriaceae (EB) throughout the sausage manufacturing process to determine high-risk stages and efficiency of existing in-plant interventions. Salmonella serotypes and antimicrobial susceptibility were evaluated on a subset of isolates recovered at the end phases of sausage production. In each collection, samples were taken from the carcasses of eight sows through 11 stages of sausage manufacturing. A total of 830 samples were cultured. Thirty-four Salmonella were isolated from the final three production stages; of these, there were eleven serotypes. Three isolates displayed resistance to ampicillin, whereas the remainder of the isolates were pan-susceptible to the antimicrobials tested. Salmonella and EB were significantly reduced (p < 0.001) by acid washes at different stages of production, and the results point to the beneficial effects of interventions to lessen Salmonella concentrations in retail products.

Thermo-Structural Coupled Finite Element Analysis of Repair Process for Steam Turbine Blade Using Laser-Directed Energy Deposition Method

AbstractThis study presents a numerical additive manufacturing simulation aimed at simulating the shape recovery process of a steam turbine blade damaged by corrosion, using laser-directed energy deposition (LDED). The simulation integrates the finite element (FE) method with heat conduction and thermo-elastoplastic constitutive equations, incorporating phase transformation. The additive manufacturing process by LDED was modeled using the death-birth algorithm, wherein a deposition layer is defined as a virtual element. Its stiffness and thermal properties activated when the laser irradiation regions overlapped. In this study, the shape of the virtual element was determined based on the cross-sectional shape of the deposition layer manufactured under various laser conditions. To validate the numerical simulation results, additive manufacturing was conducted for one pass deposition in the width direction at the center of a cantilever-supported plate made of SUS304 steel, and the changes in displacement at the free edges with respect to the process time were compared. The obtained FE results are in good agreement with the experimental results. Finally, an FE simulation was performed for the shape recovery of a steam turbine blade thinned due to corrosion damage. The results revealed that the residual stress component becomes more compressive as the laser output decreases and scanning speed increases, which is advantageous for improving the fatigue strength of steam turbine blades.

Recent Advances in Carbon Nanotube Technology: Bridging the Gap from Fundamental Science to Wide Applications

Carbon nanotubes, as carbon allotropes distinguished by their intricate structures and exceptional physicochemical properties, have demonstrated substantial progress in recent years across diverse domains, including energy production, chemical synthesis, and environmental preservation. They exhibit notable attributes such as high thermal stability, superior adsorption capacity, and a substantial specific surface area, rendering them superb catalyst supports. Particularly in electrochemical energy storage, CNTs are extensively employed in supercapacitor electrodes owing to their elevated electrical conductivity, mechanical robustness, and electrocatalytic prowess, which facilitate significant energy storage capabilities. Their intricate pore architecture and reactive sites make functionalized carbon nanotubes well suited for synthesizing composite materials with diverse components, which are ideal for sequestering carbon dioxide from both atmospheric and indoor environments. This review presents a comprehensive examination of carbon nanotube synthesis methodologies, encompassing chemical vapor deposition, arc discharge, and laser ablation, and evaluates their impacts on the structural and functional properties of carbon nanotubes. Furthermore, this article underscores the applications of carbon nanotubes in fields such as fuel cells, photocatalysis, ammonia synthesis, dry methane reforming, Fischer–Tropsch synthesis, and supercapacitors. Despite the considerable potential of carbon nanotubes, their manufacturing processes remain intricate and costly, impeding large-scale industrial production. This review concludes by addressing the challenges in fabricating carbon nanotube composites and outlining future development prospects.

An Asymmetric Independently Steerable Wheel for Climbing Robots and Its Motion Control Method

Climbing robots, with their expansive workspace and flexible deployment modes, have the potential to revolutionize the manufacturing processes of large and complex components. Given that the surfaces to be machined typically exhibit variable curvature, good surface adaptability, load capacity, and motion accuracy are essential prerequisites for climbing robots in manufacturing tasks. This paper addresses the manufacturing requirements of climbing robots by proposing an asymmetric independently steerable wheel (AISW) for climbing robots, along with the motion control method. Firstly, for the adaptability issue of the locomotion mechanism on curved surfaces under heavy load, an asymmetric independently steerable wheel motion module is proposed, which improves the steering difficulty of the traditional independently steerable wheel (ISW) based on the principle of steering assisted by wheels. Secondly, a kinematic model of the AISW chassis is established and, on this basis, a trajectory tracking method based on feedforward and proportional–integral feedback is proposed. Comparative experimental results on large, curved surface components show that the asymmetric independently steerable wheel has lower steering resistance and higher motion accuracy, significantly enhancing the reachability of climbing robots and facilitating their application in the manufacturing of large and complex components.

Holographic direct sound printing

Direct sound printing (DSP), an alternative additive manufacturing process driven by sonochemical polymerization, has traditionally been confined to a single acoustic focal region, resulting in a voxel-by-voxel printing approach. To overcome this limitation, we introduce holographic direct sound printing (HDSP), where acoustic holograms, storing cross-sectional images of the desired parts, pattern acoustic waves to induce regional cavitation bubbles and on-demand regional polymerization. HDSP outperforms DSP in terms of printing speed by one order of magnitude and yields layerless printed structures. In our HDSP implementation, the hologram remains stationary while the printing platform moves along a three-dimensional path using a robotic arm. We present sono-chemiluminescence and high-speed imaging experiments to thoroughly investigate HDSP and demonstrate its versatility in applications such as remote ex-vivo in-body printing and complex robot trajectory planning. We showcase multi-object and multi-material printing and provide a comprehensive process characterization, including the effects of hologram design and manufacturing on the HDSP process, polymerization progression tracking, porosity tuning, and robotic trajectory computation. Our HDSP method establishes the integration of acoustic holography in DSP and related applications.

Design of scalable manufacturing process for the production of biodegradable polymeric microneedles for protein transdermal drug delivery

Introduction. Dissolving polymeric microneedles are attractive drug delivery system especially for vaccine delivery. Still there are a lot of obstacles in developing scalable manufacturing process of them.Aim. To develop a scalable manufacturing process for producing polymeric dissolving microneedles, which can enable keeping protein activity during manufacturing process.Materials and methods. Microneedles were produced from aqua solution of 20 % w.v. pullulan and 3 % w.v. polyvinyl alcohol by casting in hollow negative polyethylene terephthalate mold. Human serum albumin was chosen as a model protein for this investigation.Results and discussion. There were chosen the mode of mold filling and microneedle drying process, which can guarantee keeping of protein activity during manufacturing process.Conclusion. The designed technology can be easily scaled up and used for producing vaccine drug delivery systems, because it doesn’t contain any restraining processes.

47 Generation and Characterization of Ex Vivo Expanded Tumor-Infiltrating Lymphocytes from Renal Cell Carcinoma Tumors for Adoptive Cell Therapy

Abstract Background Autologous therapeutic tumor-infiltrating lymphocyte (TIL) therapy is a promising strategy to enhance anti-tumor immunity. Optimization of ex vivo TIL expansion could expand current immunotherapy options. Previous attempts to generate TIL in renal cell carcinoma (RCC) have been technically challenging. We applied a second-generation manufacturing process, currently used to generate the melanoma TIL product lifileucel, in RCC. Methods Resected primary and metastatic RCC samples were processed using the Gen 2 manufacturing process comprising of pre-Rapid Expansion Protocol (pre-REP) and REP steps. We assessed REP TILs for viability and performed phenotypic and functional characterization. We correlated the tumor immune microenvironment (TIME) with successful TIL expansion. Results Eight of 11 RCC samples underwent successful REP. Three failed cases demonstrated low CD8/FoxP3 ratio and high expression of PD-1 within FoxP3 cells. Expression of exhaustion markers differed between the TIME and expanded TILs; the latter had a TIM3-high/PD-1-low phenotype but retained functional capacity comparable to lifileucel. Figure: Assessment of tumor immune microenvironment (TIME) via multiplex immunofluorescence (IF). Cases that failed REP are indicated in red. (A) Representative image at 60x magnification, fluorophore colors as indicated. (B) Density of tumor-infiltrating CD8+ and FoxP3+ cells. (C) Expression of co-inhibitory exhaustion markers as a percentage of total CD8+ cells. (D) Expression of PD-1 in FoxP3+ cells. (E) Comparison of tissue TIME (dots) with TIL product post-REP (open circles) exhaustion profiles as a percentage of total CD8+ cells. Conclusions The Gen 2 manufacturing process used for lifileucel successfully expanded functional TILs from RCC samples, enabling further study in a clinical trial. TIME features such as low CD8/FoxP3 ratio and high PD-1 expression within FoxP3 cells warrant study as potential biomarkers of successful TIL expansion.

Impact of Artificial Intelligence on Mechanical Engineering: A Comprehensive Overview

Artificial Intelligence (AI) is coming to mainstream and as emerged as a transformative force in various fields not just limited including mechanical engineering. This paper provides an overview of the profound impact of AI on the practice and evolution of mechanical engineering. The usage of AI technologies in the field of mechanical engineering has potential to revolutionize traditional design, manufacturing, and maintenance processes. With AI-powered design tools engineers now can generate optimized designs faster with greater efficiency, leading to enhanced product performance and reduced development cycles. Further, Predictive/forecasting method of AI in maintenance systems facilitate early detection of equipment failures, thereby minimizing downtime and maintenance costs.

Synthesis and characterization of additively manufactured microcapsule‐reinforced polylactic acid composites for autonomous self‐healing

AbstractMaterial extrusion‐based additive manufacturing (AM) process builds the objects/structures through a precise feedstock deposition in a layer‐by‐layer manner. Polylactic acid (PLA) is a popular biodegradable feedstock in AM, while octyl methoxycinnamate (OMC) is known for its eco‐friendliness and ultraviolet (UV) protection properties. The present study focuses on the novel infusion methodology of OMC‐based microcapsules into PLA to develop self‐healing composite filaments. Post‐composition iterations, the optimum compositions for the filler and plasticizer were determined, and the filaments were extruded. Microcapsule‐infused PLA and the neat PLA samples were printed as per the American Society for Testing and Materials (ASTM) standard. The uniaxial tensile test results showed that the failure strain endured by the microcapsule‐infused samples was about 10 times more than the neat PLA counterparts. It is attributed to the effective load distribution and the complex polymerization reaction (due to the interaction of OMC with the matrix). Fracture surface morphology of the samples via optical microscopy (OM) and field emission scanning electron microscope (FESEM) affirmed the strong PLA‐OMC interface. A depreciation in the Brinell Hardness for the microcapsule‐based samples was due to the localized indenter force, causing greater damage in a narrow area than microcapsule ruptures' healing ability.Highlights The optimized composition of PLA: plasticizer:microcapsule is 1:0.04:0.05. Microcapsule‐infused PLA has improved Young's modulus and failure strain. Interaction with microcapsules improves elastic behavior and self‐healing. FESEM reveals close bonding of microcapsule with the PLA matrix.

Safety impacts of design for manufacture and assembly techniques in off-site construction

Design for manufacture and assembly (DfMA) is an approach for improving project safety performance. For off-site construction (OSC), the philosophy is increasingly becoming a preferred design approach for OSC components. However, studies examining the safety impact of DfMA in OSC are limited. This study investigated the potential effects of DfMA techniques on mitigating specific safety hazards in OSC. A literature review identified and paired DfMA techniques and the safety hazards they mitigate. Empirical data was collected using a survey to assess the identified relationships. Data was analyzed using a combination of frequencies, inferential statistics, and Cronbach’s alpha. Most respondents agreed that DfMA techniques control their pairwise safety hazards in OSC. To eliminate safety hazards and limit their socio-economic impact, contracting organisations engaged in OSC need to consider the application of DfMA in the manufacture, assembly, and disassembly processes of OSC. The study reaffirms the importance of implementing evidence-based DfMA techniques for mitigating safety hazards in developing countries where OSC is an emerging philosophy.