Advances In Additive Manufacturing Research Articles

ENHANCING 3D PRINTING THROUGH MATERIAL SELECTION

Additive manufacturing (AM) has revolutionized industries by enabling the layer-by-layer 3D printing of objects. Among the diverse materials employed in AM, polymers and their composites hold significant importance due to their wide-ranging applications in fields such as medicine, aerospace, and automotive engineering. Extensive research efforts have been dedicated to developing advanced polymer materials tailored for various AM techniques, encompassing vat photo-polymerization, material jetting, powder bed fusion, material extrusion, binder jetting, and sheet lamination. While previous reviews often focus on specific aspects, this comprehensive review offers a holistic overview of polymer material advancements in AM. The review explores notable breakthroughs in newly developed materials and their potential applications. Furthermore, it outlines the existing challenges in utilizing AM for polymer materials and identifies promising opportunities, aiming to stimulate further progress in this dynamic and transformative field. Keywords:Polymers,Composites,Vatphoto-polymerization,Additivemanufacturing,Powder bed fusion, Material jetting,Binder jetting,sheet lamination.

Investigating the effect of select alloying elements in additively manufactured Co-Cr alloy for dental prosthetics

Despite the significant advancements in additive manufacturing and its exploration of functionally graded materials (FGMs), the specific roles of W and Mo in enhancing the tribological and corrosion properties of Co-Cr alloys have remained largely underexplored, particularly in the context of dental applications. To address this, CoCrW and CoCrMo alloys were fabricated using the Laser Powder Directed Energy Deposition (LP-DED) process and subjected to a comprehensive suite of microstructural analyses, and tribological behavior followed by corrosion resistance characteristics in an artificial saliva environment. Results revealed that the inclusion of Mo contributes to finer grain sizes, increased hardness and HCP phase stabilization, thus enhancing the wear resistance. Conversely, W's presence in CoCr alloys was found to bolster corrosion resistance which confirms that a synergistic approach of novel alloy development combining W and Mo can be impactful to enhance the overall performance of Co-Cr alloy-based parts. Based on author’s knowledge, this is the first time the effect of W and Mo on additively manufactured Co-Cr alloy has been presented in a comprehensive way combining manufacturing, materials characterization and performance analyses in a context of application in dental prosthetics.

Challenges and Advancements in Additive Manufacturing of Nylon and Nylon Composite Materials: A Comprehensive Analysis of Mechanical Properties, Morphology, and Recent Progress

Challenges and Advancements in Additive Manufacturing of Nylon and Nylon Composite Materials: A Comprehensive Analysis of Mechanical Properties, Morphology, and Recent Progress

Microstructural characteristics and properties of wire arc additive manufactured 304L austenitic stainless steel cylindrical components by different arc welding processes

Wire arc additive manufacturing (WAAM) is an advanced additive manufacturing (AM) technology that offers low cost and high deposition rates, making it suitable for building large metal parts for structural engineering applications. However, various welding procedures result in differing heat inputs and repetitive heating treatments throughout the deposition process, which can affect the microstructural and mechanical characteristics of the parts. In the current study, cylindrical parts made of 304L austenitic stainless steel (ASS) were manufactured using the WAAM technique, employing both gas metal arc welding (GMAW) and cold metal transfer (CMT) processes. This study explores the correlation between WAAM techniques and their effects on the bead geometry, microstructure and mechanical properties. The microstructure of the cylinders consisted of vertically growing austenite dendrites with residual ferrite (δ) within the austenite (γ) matrix. Compared to the bottom region (region ①), the top region (region ②) contained more residual ferrite. Although the microstructural characteristics from region ① to region ② are similar, they exhibit different ferrite morphologies. The rapid cooling rate in the CMT-AM process resulted in finer structures and a greater presence of ferrite phases in both regions compared to the GMAW-AM method. Cylinders produced by the CMT process displayed nearly uniform properties across both regions and demonstrated superior tensile properties, hardness, and impact toughness relative to those made using the GMAW technique. The WAAM 304L ASS cylinders also showed enhanced performance compared to stainless steel manufactured using traditional industrial forging standards, indicating that WAAM-processed 304L ASS cylinders are suitable for industrial applications.

Improving the Flexibility of Ship Propellers Additively Manufactured from High-Density Polyethylene/Long Carbon Fiber Composites by Prepreg Coating.

In efforts to achieve the goal of reducing ship emissions in the fight against climate change, reducing fuel consumption by making ships lighter is stated as one of the solutions. In this study, the possibilities of making composite equivalents of propellers, which are the most complex ship elements and traditionally produced from metal materials, are investigated with the advantages of additive manufacturing, which offers a rapid production opportunity for such forms. In this way, a lighter composite propeller and, therefore, a lighter ship will be achieved, and negative environmental impacts, especially harmful emissions, will be reduced. In the study, a 1/14-scale ship propeller was produced through the material extrusion method of additive manufacturing using an HDPE composite containing long carbon fiber with a 15% weight fraction. An attempt to reduce flexibility with an epoxy-carbon fabric prepreg coating was made, as the flexibility has negative effects on the performance of the produced propeller. The propeller tunnel test showed that the applied carbon fabric epoxy prepreg helped to improve the propeller's performance by decreasing the flexibility of the propeller and reducing the deformation at the tips. At the same time, the propeller weight was decreased by 60% compared to its metal counterparts.

The effect of weld heat input on the microstructure and mechanical properties of wire arc additively manufactured 15-5PH stainless steel

AbstractPrecipitation hardening (PH) stainless steels, such as 15-5PH, have a high strength combined with excellent corrosion resistance. These properties make them valuable in critical industries such as defence, construction, aerospace, energy and maritime. Recent advancements in additive manufacturing (AM) technology enable the rapid and cost-effective production of components. In the case of 15-5PH components manufactured using wire arc additive manufacturing (WAAM), the as-deposited mechanical properties are not suitable at present for industrial applications. This paper explores the mechanical properties of this process and alloy combination without post weld heat treatment with the aim of eventual adoption in this condition by industry. The impact of weld heat input on the microstructure and mechanical properties of stainless steel 15-5PH produced using WAAM was investigated. The microstructure was examined using hardness testing in addition to optical and electron microscopy. Furthermore, mechanical properties were measured with tensile and impact testing. Investigations were conducted on material produced using weld heat inputs of 0.223 kJ/mm and 0.565 kJ/mm. These results indicate that reducing the weld heat input leads to a minor decrease in strength but an 80% increase in impact toughness. This reduction in weld heat input is correlated with a 50% reduction in volume fraction of δ-ferrite while also noting a 55% increase in carbide precipitates. In addition, the fracture surfaces were predominantly cleavage or quasi-cleavage in morphology.

Quality by Design Considerations for Drop-on-Demand Point-of-Care Pharmaceutical Manufacturing of Precision Medicine.

Distributed and point-of-care (POC) manufacturing facilities enable an agile pharmaceutical production paradigm that can respond to localized needs, providing personalized and precision medicine. These capabilities are critical for narrow therapeutic index drugs and pediatric or geriatric dosing, among other specialized needs. Advanced additive manufacturing, three-dimensional (3D) printing, and drop-on-demand (DoD) dispensing technologies have begun to expand into pharmaceutical production. We employed a quality by design (QbD) approach to identify critical quality attributes (CQAs), critical material attributes (CMAs), and critical process parameters (CPPs) of a POC pharmaceutical manufacturing paradigm. This theoretical framework encompasses the production of active pharmaceutical ingredient (API) "inks" at a centralized facility, which are distributed to POC sites for DoD dispensing into/onto delivery vehicles (e.g., orodispersible films, capsules, single liquid dose vials). Focusing on the POC dispensing/dosing processes, QbD considerations and cause-and-effect analyses identified the dispensed API quantity and solid-state form (CQAs), as well as the nozzle diameter, system pressure channel, and number of drops dispensed (CPPs) for detailed investigation. Final assay quantification and content uniformity CQAs were measured from demonstrative levothyroxine sodium single-dose liquid vials of glycerin/water, meeting the standard acceptance values. Each POC facility is unlikely to maintain full quality control laboratory capabilities, requiring the development of appropriate atline or inline methods to ensure quality control. We developed control strategies, including atline ultraviolet-visible (UV-vis) verification of the API ink prior to dispensing, inline drop counting during dispensing, intermediate atline-dispensed volume checks, and offline batch confirmation by liquid chromatography-tandem mass spectrometry (LC-MS/MS) following production.

Efficient dynamic topology optimization of 2D metamaterials based on a complementary energy formulation

The advent of additive manufacturing has revolutionized the design and development of hierarchical structures, with potential applications in compliant, auxetic, and band-gap structures. This paper presents an innovative approach to developing a dynamic Topology Optimization (TO) framework for designing printable lattice structures that exhibit specific dynamic properties. Utilizing parametrically defined filament-based unit cell structures for topology optimization, we achieve desired natural frequency bandgaps in the structures composed of these unit cells. To enhance computational efficiency, we employ a complementary energy-based formulation to (semi)analytically derive the flexibility and stiffness matrices of the unit cell structure, thus, eliminating extensive finite element discretization. Consequently, a wide variety of parametrically defined filament-based meso-structures can be mathematically explored. We apply this innovative framework specifically for band-gap maximization of 2D lattice structures. By tuning the geometry within each cell using TO, we maximize the band gap. Our results show the potential of this approach to create more efficient and effective hierarchical structures with desired band-gap properties.

Additive manufacturing of ultrahigh-resolution Poly(ε-caprolactone) scaffolds using melt electrowriting

Melt electrowriting (MEW) is an advanced additive manufacturing technology that produces high-resolution scaffolds for medical applications. Although there are many valuable parameter groups for MEW, the corresponding principles need to be clarified to improve the success of printing high-fidelity scaffolds. To this end, we investigate the print limit of MEW with respect to the minimum interfiber distance and the maximum print period based on a medical-grade poly(ε-caprolactone) material. The results indicate that relatively large turning loops and low turning speeds improve the print accuracy of the scaffolds; however, excessively large turning loops and low turning speeds result in fiber accumulation on the edge of the scaffolds, resulting in print failure. The turning loops with 500 μm in diameter and turning speeds of 0.625 × CTS (critical translation speed) can achieve well-defined MEW scaffolds with an interfiber distance down to 25 μm. For printing such high-resolution scaffolds, the constant printing process can last one week. Fiber placement gets random when the fiber diameter is larger than 2.5 μm, caused by the melt polymer degradation and shear thinning in the printing process. Additionally, we verify that the method of charge neutralization is not beneficial for improving the fiber overlay. This is a fundamental study clarifying the principles of printing high-resolution MEW scaffolds, being capable of extending the application of the MEW products.

Theory and inverse design of microperforated panels comprising arbitrary axial pore profiles for broadband low-frequency sound absorption

Toward identifying efficient sound absorbers, we have formulated and analyzed the micro-perforated panels (MPPs) comprising cylindrical pores of arbitrary axial profiles for out-of-plane wave propagation. First, the forward problem was solved wherein an exact analytical expression for the absorption coefficient α was developed for these MPPs. The dependence of α was analyzed for various profiles comprising convex and concave-shaped sections including divergent and convergent linear and sinusoidal profiles, conic sections, Kilroy, and chirp shapes. The MPPs with pores having a diverging shape at the entrance were found to have higher sound absorption. The non-symmetric fluctuations in the profile led to fluctuations in the spectrum of α. Aiming to address the long-standing challenge of low-frequency sound absorption, we solved the inverse problem to identify the axial profile of the cylindrical pore for maximum sound absorption for frequencies up to 2500 Hz. Given the advances in additive manufacturing, the results of this comprehensive work help in designing MPPs comprising complex-shaped pores suitable for a particular spectral regime.

Mechanical properties of additively manufactured polymeric composites using sheet lamination technique and fused deposition modeling: A review

AbstractNowadays, it is possible to produce products with complex geometries, thanks to the experts who have continuously explored the advancements in additive manufacturing (AM) techniques. This review helps readers understand the opportunities and difficulties associated with developing parts for various industries, including aerospace, tooling, electronics, and biomedicine. The present work describes the landscape of polymeric composites using laminated object manufacturing (LOM) and fused deposition modeling (FDM). This paper discusses recent publications in the realm of AM related to composite fabrication, materials, techniques, functionality, and future scope. The effects of nanofiller reinforcement on the mechanical properties of composites have been thoroughly investigated. Furthermore, FDM process parameters such as layer thickness, infill speed, nozzle temperature, and raster angle have also been considered. Finally, the challenges and potential applications of LOM and FDM of additively manufactured composites have been summarized.

Incorporating boron carbide into fused silica imparts multiple mechanisms to facilitate vat photopolymerization

Rapid manufacturing of complex-shaped ceramic components has long been a pressing issue in the aerospace industry. Recent progress in this direction takes advantage of additive manufacturing, by employing vat photopolymerization (VPP) followed by sintering. Here we demonstrate a new recipe/protocol that enables the VPP route to deliver silica products of high relative density as well as high strength. This is achieved by incorporating 2.5wt.% of boron carbide (B4C) into the fused silica slurry, which offers beneficial effects in multiple fronts. During the VPP process, the added black B4C, together with the refractive index difference between the two components in the mixture, effectively increased the light absorbance. Upon sintering, the boron oxide produced by the oxidation of B4C played the role of a sintering aid. The boron oxide also helped to suppress the crystallization of the amorphous silica and therefore the formation of cracks. As a result, the overall quality (forming precision, density, strength and dielectric constant) of the product surpasses by far those prepared previously via VPP-sintering. In particular, the flexural strength reached 60.7MPa, a factor of 2.5 better than the previously reported highest value. Extending the success above further, we have manufactured a complex-structured silica radome, as a demonstration of the high-quality products achievable for practical applications.

Review on Additive Manufacturing Process in Aircraft Industries

This paper explores the feasibility of implementing 3D printing technology for manufacturing seat buckles in the Airbus A380. While additive manufacturing has gained attention for its versatility, safety-critical components require rigorous testing and certification. Through a comprehensive review of literature and expert interviews, this study analyzes the viability of 3D printing for seat buckle production. The results indicate that traditional manufacturing methods, such as injection molding and forging, remain the preferred choices due to their established reliability and quality control procedures. The aviation industry places the utmost importance on safety and reliability, especially in the manufacturing of safety-critical components like seat buckles. This paper examines the potential integration of 3D printing technology into the production process of seat buckles for the Airbus A380, considering the stringent certification requirements and performance expectations. A literature review encompassing additive manufacturing techniques, aerospace certification processes, and current seat buckle manufacturing practices was conducted. Expert interviews were also conducted to gather insights from industry professionals with expertise in aerospace manufacturing. The analysis revealed that conventional manufacturing methods such as injection molding and forging are currently preferred for seat buckle production in the Airbus A380 and other aircraft parts. These methods have established reliability and quality control procedures, ensuring compliance with rigorous safety standards. Although 3D printing has found success in prototyping and non-critical components, its application in safety-critical components like seat buckles is limited. The decision to favor traditional manufacturing methods for seat buckle production in the Airbus A380 is driven by the need for extensively tested and certified components. Safety-critical parts undergo stringent testing to guarantee their performance under various operating conditions. While 3D printing offers design flexibility and reduced lead times, further research and development is necessary to ensure its viability in safety-critical applications. At present, 3D printing technology is not widely employed for manufacturing seat buckles in the Airbus A380. Traditional methods provide the required reliability and quality control procedures. However, ongoing advancements in additive manufacturing may present future opportunities for incorporating 3D printing technology into safety-critical applications within the aerospace industry. Further research and development are necessary to explore these possibilities.

Frontiers of Laser‐Based 3D Printing: A Perspective on Multi‐Photon Lithography

AbstractLasers are instrumental in enabling precise processing and fostering the development of new technologies. Particularly, ultrafast lasers, due to their unique interaction with matter, can achieve not only exceptional spatial precision but also meticulously determine the degree of modification. A prime example of this is laser‐based 3D printing through multi‐photon lithography (MPL). This approach remarkably enables the printing of true 3D structures at the micro‐ and nanoscale, without the need for masks or cumbersome tools, simply by using computer‐aided designs. Owing to these unique capabilities, MPL has emerged as a powerful manufacturing technique across various multidisciplinary fields. The ongoing growth in MPL's utilization has led to notable advancements in printing highly complex structures on different substrates, as well as improvements in resolution and throughput, and the development of novel photosensitive materials, which impressively facilitated MPL's expansion into broader fields over the last few years. In this perspective article, the aim is to highlight these advancements and recent trends in MPL. The current challenges of MPL will be explored, which need to be addressed to ensure its further integration into advanced Additive Manufacturing at the micro‐ and nanoscale. The future perspectives and opportunities of MPL as a laser‐based 3D printing approach will also be discussed.

Single and repeated impact behavior of material extrusion-based additive manufactured PLA parts

The advent of Additive Manufacturing (AM) for producing components or parts made of thermoplastic polymers have increased the necessity of a deep knowledge of their mechanical properties. In particular, the mechanical performance under impact loads is still not fully investigated and requires a thorough knowledge. In this paper, polylactic acid (PLA) samples were produced by material extrusion (MEX) technology and subjected to low velocity impact (LVI) tests by using different impactors’ geometries and impact energies. Initially, the PLA filament and MEX-printed samples were subjected to a physico-chemical evaluation through TG, DSC and FTIR analyses. The FTIR and DSC analyzes highlighted phase transitions specific to semicrystalline PLA polymer, while the TG analysis showed that the used printing temperature (220 °C) does not affect the thermal behavior of the filament. The mechanical assessment consisted of single and repeated LVI tests on the same sample until total penetration or failure were reached. The samples subjected to impact tests were analyzed by digital radiography to detect the internal damage and failure mechanisms. The impactor shape has a strong effect on the mechanical strength of the tested samples. For single impacts, the peak load was higher for the 20 mm diameter hemispherical impactor (H20), while the lowest value was experienced by the samples tested with 10 mm diameter hemispherical impactor (H10). The lowest value of specific absorbed energy was recorded with the truncated conical (TC) impactor. For multiple impacts, with the H10 and TC impactors it was possible to impact the sample 4 times, respectively; 2 times with the H20 impactor.

PROCESS DEVELOPMENT IN MECHANICAL ENGINEERING: INNOVATIONS, CHALLENGES, AND OPPORTUNITIES

Process development in mechanical engineering encompasses a broad spectrum of innovations, challenges, and opportunities that drive advancements in various industries. This review delves into the multifaceted landscape of process development within mechanical engineering, highlighting key themes and trends. Innovations in process development are propelled by the continuous quest for efficiency, sustainability, and enhanced performance. Advances in additive manufacturing, automation, and digitalization have revolutionized traditional manufacturing processes, enabling the creation of complex geometries with unprecedented precision and speed. Additive manufacturing techniques such as 3D printing offer versatility in material selection and design freedom, facilitating rapid prototyping and customization while minimizing material wastage. Automation technologies, including robotics and AI-driven systems, optimize production workflows, augmenting productivity and reducing human error. Moreover, digital twins and simulation tools empower engineers to simulate and optimize processes virtually, accelerating product development cycles and minimizing costly experimentation. However, alongside these innovations, mechanical engineers face a myriad of challenges. The integration of new technologies often requires substantial investment in infrastructure and workforce training. Quality control and assurance remain critical concerns, particularly in additive manufacturing, where ensuring part integrity and repeatability is paramount. Furthermore, the sustainability implications of emerging processes must be carefully evaluated to mitigate environmental impact and resource depletion. Despite these challenges, process development in mechanical engineering presents abundant opportunities for growth and advancement. The rise of Industry 4.0 initiatives fosters collaboration between academia, industry, and government, driving research and development efforts towards sustainable and interconnected manufacturing ecosystems. The advent of advanced materials, including composites and biomaterials, unlocks new possibilities for lightweight structures, enhanced performance, and tailored functionalities. Additionally, the pursuit of circular economy principles promotes resource efficiency and waste reduction throughout the product lifecycle. In conclusion, process development in mechanical engineering is characterized by a dynamic interplay of innovation, challenges, and opportunities. By embracing emerging technologies, addressing key challenges, and leveraging collaborative partnerships, mechanical engineers can drive transformative change across industries, paving the way for a more efficient, sustainable, and interconnected future.
 Keywords: Process, Development, Mechanical, Engineering, Innovation, Review.

An Optimization Study Focused on Lattice Structured Custom Arm Casts for Fractured Bones Inspiring Additive Manufacturing

In case of fractures, cracks or damage to bone tissues, it is important to use casts, fixatives and protective equipment. Especially in cases where long-term use of casts is required, soft tissue wounds may occur in the human body due to their moisture and airtight structure. For this reason, the use of casts with custom designs, breathable materials, and high mechanical properties has become widespread in recent years. This study focuses on the design of custom arm casts using advanced additive manufacturing technologies and lightweight materials. By utilizing Voronoi lattice structures and hexagonal surface meshes, optimized designs adaptable to additive manufacturing were obtained from a standard arm cast. All cast geometries were investigated under 196N and 380N forces. Then, the impact of a 100g and 1000g concrete piece with a speed of 12.5m/s on the arm cast was investigated. As a result of the analyzes, stress, impact plate velocities, deformation, strain and deformation energy were evaluated. The results showed that the designed arm casts have up to 60% better impact strength compared to conventional arm casts. Based on the findings of this study, the use of custom arm casts with optimized lattice structures designed for additive manufacturing will demonstrate high performance.

Additive manufacturing of Invar 36 alloy

Invar 36 alloy, renowned for its ultra-low coefficient of thermal expansion (CTE), is a functional Fe–Ni alloy that finds wide applications in aerospace and precision instruments. Additive manufacturing (AM), as a rapid digital manufacturing process, can efficiently and flexibly fabricate Invar 36 alloy parts with complex geometric and exceptional properties. Considering the advantages of AM and the increasing interest and demand for Invar 36 alloy parts fabrication by AM in recent years, it is imperative to provide a comprehensive summary of the current research status and technological advancements pertaining to AM Invar 36 alloy. Firstly, an overview of the AM processes currently employed for fabricating Invar 36 alloy is provided, including laser powder bed fusion, selective laser sintering, directed energy deposition, cold spray additive manufacturing, wire arc additive manufacturing, and binder jetting. Additionally, the microstructure, mechanical properties, and CTE of Invar 36 alloy manufactured by AM are summarized. Even eliminating the post heat treatment, the as-printed Invar 36 alloy can achieve excellent low CTE and mechanical properties, comparable to or exceeding traditional manufacturing processes. Moreover, the advantages and research progress of AM Invar 36 alloy composites are introduced. Enhancing mechanical properties while reducing CTE is a common challenge for both AM Invar 36 alloy and Invar composites. Finally, the technical gaps, research trends, and potential applications of AM Invar 36 alloy are summarized and prospected.

A partially hollow BCC lattice structure with capsule-shaped cavities for enhancing load-bearing and energy absorption properties

Lattice structures have gained larger design space and wider application in aerospace, automobile, civil and other engineering fields due to the advancements in additive manufacturing (AM) technology. Seeking the optimal lattice structure configuration for the purpose of enhancing mechanical performance holds paramount importance. The hollow lattice structure possesses high material utilization efficiency, but often suffers from premature failure at the node interconnections. In this paper we propose a partially hollow lattice structure (PHBCC) with solidified nodes and capsule-shaped cavities in the middle of truss components. Quasi-static compression tests were performed on the partially hollow body-centered cubic (BCC) lattices manufactured via selective laser melting technology (SLM). The effects of various geometric parameters were analyzed through finite element simulations. The findings demonstrate that the introduced PHBCC lattice exhibits enhanced mechanical properties. Specifically, there is an observed increase of 92%, 51.9%, and 22.8% in terms of specific stiffness, specific strength, and specific energy absorption, respectively, in comparison to the conventional BCC and hollow BCC (HBCC) structure. Notably, the proposed PHBCC lattice displays superior energy absorption capacity compared to a majority of existing lattice structures.

Standard Tessellation Language-Free Adaptive Slicing Scheme for Additive Manufacturing of Cellular Materials

Abstract In recent years, advances in additive manufacturing (AM) techniques have called for a scalable fabrication framework for high-resolution designs. Despite several process-specific handful design approaches, there is a gap to fill between computer-aided design (CAD) and the manufacturing of highly detailed multiscale materials, especially for delicate cellular material design. This gap ought to be filled with an avenue capable of efficiently slicing multiscale intricate designs. Most existing methods depend on the mesh representation, which is time consuming and memory hogging to generate. This article proposes an adaptive direct slicing (mesh-free) pipeline that exploits the function representation (FRep) for hierarchical architected cellular materials design. To explore the capabilities of the presented approach, several sample structures with delicate architectures are fabricated using a stereolithography (SLA) printer. The computational efficiency of the proposed slicing algorithm is studied. Furthermore, the geometry frustration problem brought by the connection of distinct structures between functionally graded unit cells at the microscale level is also investigated.