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Additive manufacturing (AM) is the fabrication of real three-dimensional objects from metals, ceramics, or plastics by adding material, usually as layers. There are several variants of AM; among them material extrusion (ME) is one of the most versatile and widely used. In MEAM, molten or viscous materials are pushed through an orifice and are selectively deposited as strands to form stacked layers and subsequently a three-dimensional object. The commonly used materials for MEAM are thermoplastic polymers and particulate composites; however, recently innovative formulations of highly-filled polymers (HP) with metals or ceramics have also been made available. MEAM with HP is an indirect process, which uses sacrificial polymeric binders to shape metallic and ceramic components. After removing the binder, the powder particles are fused together in a conventional sintering step. In this review the different types of MEAM techniques and relevant industrial approaches for the fabrication of metallic and ceramic components are described. The composition of certain HP binder systems and powders are presented; the methods of compounding and filament making HP are explained; the stages of shaping, debinding, and sintering are discussed; and finally a comparison of the parts produced via MEAM-HP with those produced via other manufacturing techniques is presented.

Additive manufacturing is a layer-by-layer strategy enabling the advanced design and fabrication of complex 3D objects and structures, overcoming geometry limitations and reducing waste production compared to conventional technologies. Among various additive manufacturing technologies, digital light processing (DLP), is an additive manufacturing technology used to print photopolymer parts, using a projected light source to cure an entire layer at once. Initially developed for pure resins, recent advances have demonstrated the potential of DLP in the polymerization of ceramic and metal-loaded suspensions, enabling the fabrication of ceramic and metal components after proper debinding and sintering. Such flexibility increases the potential of DLP for different applications, ranging from dental implants and bone scaffolds to smart biomaterials for soft robotics, smart wearables, and microfluidic devices. The review provides an overview of DLP technology and its recent advances; specifically, the review covers the photopolymer properties, the ceramic and metallic feedstock preparation, and the light-matter interaction mechanism underpinning the printing and post-processing steps. Finally, a description of the current application is provided and complemented with future perspectives.

The accelerated growth of 3D printing technologies has revolutionized the potential of ceramic materials, offering unprecedented control over microstructures, saving labor cost, material, and process time. Stereolithography-based 3D printing has grown to fabricate advanced ceramics materials with the flexibility of mass production. 3D printing generally offers unprecedented versatility, fast-printing tangible design, custom freedom, and excellent laying accuracy. More specifically, ceramic materials offer unique mechanical properties to make them superior for various applications. A description of how digital light processing (DLP) 3D printing can play a pivotal role in fabricating oxide ceramics in terms of complex shape, material used, ceramic resin, debinding and sintering control, and theoretical background for accuracy and high resolution is presented along with their distinctive features. Within 2021–2026, the DLP printing market is expected to reach a GR of 5.9%. The current findings shed light on the potential of DLP printing open windows in ceramic materials, which is are very promising, a step forward to achieving sophisticated structures with great versatility and efficiency. This review article is devoted to ceramics and their oxides (Al 2 O 3 , ZrO 2 , and kaolin), non-oxides (Si 3 N 3 and SiC), and Al 2 O 3 -reinforced ZrO 2 composites, whose morphologies are elaborated in depth. Some key factors are prioritized, such as the ceramic resin, photoinitiator, monomers, and suspension, which may facilitate the scalability of the desired printing. A summary table concludes with the operating conditions, materials, and fundamental aspects of physiochemical and thermomechanical features in large-scale manufacturing.

Material extrusion additive manufacturing of metal (metal MEX), which is one of the 3D printing processes, has gained more interests because of its simplicity and economics. Metal MEX process is similar to the conventional metal injection moulding (MIM) process, consisting of feedstock preparation of metal powder and polymer binders, layer-by-layer 3D printing (metal MEX) or injection (MIM) to create green parts, debinding to remove the binders and sintering to create the consolidated metallic parts. Due to the recent rapid development of metal MEX, it is important to review current research work on this topic to further understand the critical process parameters and the related physical and mechanical properties of metal MEX parts relevant to further studies and real applications. In this review, the available literature is systematically summarised and concluded in terms of feedstock, printing, debinding and sintering. The processing-related physical and mechanical properties, i.e., solid loading vs. dimensional shrinkage maps, sintering temperature vs. relative sintered density maps, stress vs. elongation maps for the three main alloys (316L stainless steel, 17-4PH stainless steel and Ti-6Al-4V), are also discussed and compared with well-established MIM properties and MIM international standards to assess the current stage of metal MEX development.

Fused filament fabrication (FFF) combined with debinding and sintering could be an economical process for three-dimensional (3D) printing of metal parts. In this paper, compounding, filament making, and FFF processing of feedstock material with 55% vol. of 17-4PH stainless steel powder in a multicomponent binder system are presented. The experimental part of the paper encompasses central composite design for optimization of the most significant 3D printing parameters (extrusion temperature, flow rate multiplier, and layer thickness) to obtain maximum tensile strength of the 3D-printed specimens. Here, only green specimens were examined in order to be able to determine the optimal parameters for 3D printing. The results show that the factor with the biggest influence on the tensile properties was flow rate multiplier, followed by the layer thickness and finally the extrusion temperature. Maximizing all three parameters led to the highest tensile properties of the green parts.

This paper proposed a method for preparing subtle and complex lattice structure Al2O3 ceramic via digital light processing (DLP) 3D printing technology. The solid-phase mass fraction of Al2O3 ceramic slurry and the porosity of the green body reached 52% and 83%, respectively. According to the TG-DSC curve and two-way analysis of variance, the optimum technological parameters for debinding and sintering of Al2O3 ceramic green body were determined. The same shrinkage of Al2O3 ceramic prepared by pressureless sintering in all directions was confirmed. The density of sintered lattice structure Al2O3 ceramic was 95%, and the diameter of the lattice structure strut was about 170 μm. XRD and Raman spectrum showed that the crystal phase of the sintered Al2O3 ceramic was α-phase, which has a good crystal quality. SEM results revealed a high density without significant pores and cracks sintered ceramic. The strict complex structure Al2O3 ceramic prepared by DLP technology had a compact microstructure and similar to the mechanical strength of Al2O3 prepared via the conventional shaping method, thereby providing an effective method for fabricating large specific surface area ceramic radiators and fine ceramic components in other fields.

The selective laser melting (SLM) process is of great interest for fabrication of metal parts, and a number of studies have been conducted to provide in-depth understanding of how stainless steel 316L parts can be fabricated using this powder-bed-fusion-based additive manufacturing (AM) process. In comparison with SLM stainless steel 316L, this paper introduces an innovative AM process for making austenitic stainless steel 316L parts using a metal–polymer composite filament (Ultrafuse 316LX). Stainless steel 316L metal specimens were printed using a material extrusion (FDM)-based three-dimensional (3D) printer loaded with Ultrafuse filament, followed by an industry-standard debinding and sintering process. Tests were performed to understand the material properties, such as hardness, tensile strength, and microstructural characteristics. Part shrinkage was also analyzed based on the features of the FDM stainless steel 316L component. A preliminary guideline on how to select among these two alternative AM processes for fabrication of metal parts is discussed.

Stereolithography (SL) is a technique allowing additive manufacturing of complex ceramic parts by selective photopolymerization of a photocurable suspension containing photocurable monomer, photoinitiator, and a ceramic powder. The manufactured three-dimensional object is cleaned and converted into a dense ceramic part by thermal debinding of the polymer network and subsequent sintering. The debinding is the most critical and time-consuming step, and often the source of cracks. In this study, photocurable alumina suspensions have been developed, and the influence of resin composition on defect formation has been investigated. The suspensions were characterized in terms of rheology and curing behaviour, and cross-sections of sintered specimens manufactured by SL were evaluated by SEM. It was found that the addition of a non-reactive component to the photocurable resin reduced polymerization shrinkage and altered the thermal decomposition of the polymer matrix, which led to a reduction in both delamination and intra-laminar cracks. Using a non-reactive component that decomposed rather than evaporated led to less residual porosity.

Recently, various additive manufacturing (AM) methods with a wide range of capabilities have been employed to produce metallic objects. Metals are a popular choice among AM materials due to their superior properties, despite being more challenging to print. Reduced product cost, the possibility for quick production and prototyping, and the capability of a produced component by high accuracy in a broad variety of shapes, geometrical complexity, size, and material are all advantages of metal AM technology. Metal fused deposition modeling (metal FDM) is a relatively new technique based on the widely used FDM process. It is a relatively low-cost competitor to other metal AM techniques such as selective laser melting (SLM). This review paper has explored the most recently issued publications in this extrusion-based metal additive manufacturing (EAM) technique. The main parameters in feedstock preparation, deposition and 3D printing, debinding, and sintering phases of the metal FDM process will be discussed and their influence on the mechanical and microstructural characteristics of the 3D-printed parts. Furthermore, the application of finite element modeling for metal FDM process analysis is explored. Finally, the challenges and gaps in the manufacturing of components and obtaining desired characteristics have been presented.

In the present study, an additive manufacturing process of copper using extrusion 3D printing, solvent and thermal debinding, and sintering was explored. Extrusion 3D printing of metal injection moulding (MIM) feedstock was used to fabricate green body samples. The printing process was performed with optimized parameters to achieve high green density and low surface roughness. To remove water-soluble polymer, the green body was immersed in water for solvent debinding. The interconnected voids formed during solvent debinding were favorable for removing the backbone polymer from the brown body during thermal debinding. Thermal debinding was performed up to 500 °C, and ~ 6.5% total weight loss of the green sample was estimated. Finally, sintering of the thermally debinded samples was performed at 950, 1000, 1030, and 1050° C . The highest sintering temperature provided the highest relative density (94.5%) and isotropic shrinkage. Micro-computed tomography (μCT) examination was performed on green samples and sintered samples, and qualitative and quantitative analysis of the porosity confirmed the benefits of optimized printing conditions for the final microstructure. This work opens up the opportunity for 3D printing and sintering to produce pure copper components with complicated shapes and high density, utilizing raw MIM feedstock as the starting material.