Progress in Additive Manufacturing

Krishna, R. S.; Rehman, Asif Ur; Mishra, Jyotirmoy; Saha, Suman; Korniejenko, Kinga; Rehman, Rashid Ur; Salamci, Metin Uymaz; Sglavo, Vincenzo M.; Shaikh, Faiz Uddin Ahmed; Qureshi, Tanvir S.

doi: 10.1007/s40964-024-00703-zpmid: N/A

Increasing pollution poses enormous pressure on the global ecosystem, with a need to limit the carbon emissions from the construction materials industry. Mitigation of this carbon is possible by converting industrial wastes into alternative cement and optimisation in the building process. Taking this into account, advancement is taking place in sustainable geopolymer composites-based additive manufacturing (AM) technology. Typical precursors for geopolymer binder are industrial waste by-products (such as slag, fly ash, and metakaolin). In another aspect, AM entails several benefits such as easy fabrication, freedom of design, the ability to generate sophisticated structural elements and reduce: expenses, time, waste generation, and labor demands. This review journal paper on geopolymer AM presents a bibliometric study followed by an overview of AM methods and influencing parameters, techniques in geopolymer AM (such as extrusion and powder bed), materials, improvements in AM process, and fresh-state and hardened-state properties. Recent developments in AM processes within the geopolymer are critically discussed while investigating the properties and applications of the same. The discussion includes an analysis pinpointing research gaps essential in developing geopolymer AM.Graphical abstract[graphic not available: see fulltext]

Gahletia, Sumit; Garg, Ramesh Kumar

doi: 10.1007/s40964-024-00706-wpmid: N/A

This study aims to identify and address the critical barriers that occurred during the fabrication of orthodontic retainers and plays a significant role in connecting patient care with evidence-based dentistry as engineers, dentists and researchers all learn to create, program and mash materials and products. Articles addressing the problems faced during the fabrication of orthodontic retainers using 3D Scanning and rapid prototyping methods were compiled and analysed. The study found that orthodontic retainers with more clinically acceptable deviations can be achieved by dismantling the critical barriers encountered during manufacturing. Overcoming the critical manufacturing barriers can revolutionize orthodontic retainers but raises concerns about exacerbating disparities as access to innovative digital manufacturing may not be equitable, deepening the divide in preventive dentistry. This research contributes to the field of orthodontics by providing valuable insights and recommendations for integrating patient-centred care with digital manufacturing to enhance preventative oral healthcare.

Wakjira, Yosef; Cioni, Arturo; Lemu, Hirpa G.

doi: 10.1007/s40964-024-00714-wpmid: N/A

Bone tissue engineering provided the innovative solution to regenerate bone tissue using scaffolds (porous) structures. This research investigates optimization, additive manufacturing methods and the application areas of triply periodic minimal surface-based (TPMS) porous structures in the broad field of tissue engineering through literature review. The properties of TPMS structures are compared with more classical strut-based structures. Also, information on how TPMS can be formulated and how they can be designed to obtain desired properties are presented. Attention is dedicated to the topological optimization process and how it can be applied to scaffolds to further increase their biomechanical properties and improve their design through density, heterogenization, and unit cell size grading. Common numerical algorithms as well as the difference between gradient-based and non-gradient-based algorithms are proposed. Efforts also include the description of the main additive manufacturing technologies that can be utilized to manufacture either stochastic or periodic scaffolds. The information present in this work should be able to introduce the reader to the use of TPMS structures in tissue engineering.

Mahajan, Amit; Devgan, Sandeep

doi: 10.1007/s40964-024-00722-wpmid: N/A

Additive manufacturing processes have gained popularity for their ability to create complex geometries, but they often introduce unique challenges in terms of material properties and surface quality. The corrosion performance of additive manufactured (AM) materials is a complex topic influenced by multiple factors. Corrosion resistance is a significant parameter for industries like aerospace, automotive, and biomedical, where the reliability and durability of components are critical. Surface engineering poses several challenges for enhancing the corrosion resistance of AM materials such as microstructural heterogeneity, material selection, post-processing effects, localized corrosion susceptibility etc. The aim of this paper is to examine the corrosion behavior of the additive manufactured metals, alloys, polymers, and composites. Further, recent research on the surface engineering on these materials to enhance the corrosion resistance are also reviewed. According to the reported studies, surface alteration of AM metals and alloys by ultrasonic acid etching, plasma, thermal, and laser treatment showed excellent corrosion resistance. Different coatings such as copper, and nickel on AM polymers provided superior corrosion protection. Moreover, modification of the AM composite surface by sol–gel process or thermal treatment improved the corrosion resistance. However, future innovations offer promising avenues for improvement in corrosion resistance of AM materials. Modifying materials specifically for AM processes, employing advanced coating technologies, and integrating in situ monitoring during manufacturing are possibilities for corrosion resistance enhancement. The development of corrosion-resistant nanomaterials, novel surface modification techniques, and the integration of computational modeling into the design process hold potential for overcoming the challenges and propelling the field toward enhanced corrosion-resistant additive manufactured materials.

Berghaus, Michael; Florian, Steffen; Solanki, Keyur; Zinn, Carolin; Wang, Hongcai; Butz, Benjamin; Apmann, Hilmar; von Hehl, Axel

doi: 10.1007/s40964-024-00693-ypmid: N/A

Due to its ease of processing, the stainless steel 316L is a widely used material for the laser powder bed fusion (PBF-LB/M) process. Compared to other additive manufacturing technologies PBF-LB/M has a lot of advantages such as design freedom and high resolution of details. However, PBF-LB/M also has some disadvantages, such as a reduced build-up rate. In general, 316L provides a wide range of parameter settings used for PBF-LB/M. In this study, the manufacturing limits were approached allowing a maximum build-up rate along with a high relative density > 99% without compromising the required mechanical properties. Microstructure analyses as well as tensile tests were performed to validate this approach. This article also provides insights on defects and relative density for scanning speed above 3000 mm/s. Furthermore, it was shown that the scanning speed has a major influence on the grain size and on the texture of the specimens. For the first time, the relative density, microstructure and mechanical properties of additively manufactured 316L were determined in relation to each other for high scanning speed. A set of parameters has been found that works best with a laser power of 285 W and a scanning speed of 1250 mm/s which results in a specimen relative density of 99.2%, a yield strength of 425 MPa, a tensile strength of 586 MPa and a build-up rate of 4.64 mm3/s. The findings can be further used to enhance the mechanical properties of PBF-LB/M 316L in terms of high build-up rates.

Quarto, Mariangela; Cappellini, Cristian; Giardini, Claudio; D’Urso, Gianluca

doi: 10.1007/s40964-024-00694-xpmid: N/A

One of the main issues of Material Extrusion (MEX) production is represented by the porosity of the printed structures. This is strictly related to the deposition strategy which affects the dimensions and the continuity of the porous pattern in the inner part of the components. Having control of the porous patterns allows not only to obtain parts with fewer imperfections but also to improve the mechanical characteristics of the components. In this article, a new deposition strategy is presented which, instead of depositing equal layers, alternates deposition by distinguishing between even and odd positions of the filaments in the layer. Considering the section of the components, the new strategy can reduce the porosity by disrupting its pattern. This results in obtaining a greater number of porosities characterized by a smaller extent, and in a disintegration of the porous pattern, revealing numerous closed porosities. In general, the developed strategy allows the increment of the apparent density.

Thirugnanasambandam, Arunkumar; Dutta, Hrishikesh; Gnanasagaran, Constance L.; Kechagias, John D.

doi: 10.1007/s40964-024-00695-wpmid: N/A

This work presents the fabrication of a multi-polymer component (MPC) using polylactic acid (PLA) and polyethylene terephthalate glycol (PETG) through an additive manufacturing process. PETG was blended with PLA in weight percentages of 6%, 12%, and 18% using a twin-screw extruder to make pellets. The mixed pellets were extruded into 1.75 mm filaments for 3D printing MPCs. The MPC samples were 3D-printed using a PRATHAM 3.0 3D printer. The characteristic behavior of the MPC was compared to its base materials in terms of tensile strength, compressive strength, flexural strength, elongation-at-break, glass transition temperature, and water uptake percentage. The results revealed a marginal reduction in tensile strength with the addition of PETG to PLA. However, a noticeable enhancement (33.05%) in the elongation-at-break was achieved for the MPC containing 18 wt.% PETG compared to neat PLA. The glass transition temperature of the MPC with 18 wt.% PETG was in the range of 63–65 °C in contrast to that of neat PLA (55–58 °C), depicting an improvement of ~ 12.07%. The morphology of the fracture surface of the MPC was studied using a high-resolution scanning electron microscope (HRSEM). The results revealed ductile failure of MPC, confirming a slight brittle-to-ductile transition of the neat PLA. The outcome of this study establishes that MPC using blended filaments of multi-polymer can be successfully fabricated, achieving better ductility and thermal transition behavior than its base materials.

Curmi, Albert; Rochman, Arif; Gatt, Alfred

doi: 10.1007/s40964-024-00696-9pmid: N/A

This study determined the requisite process parameters for good-quality screw extrusion additive manufacturing (AM) of thermoplastic polyolefin (TPO) using fused granulate fabrication (FGF). TPO is a non-hygroscopic, cheaper, and less dense alternative to the well-established thermoplastic polyurethane (TPU). TPO was found to extrude correctly at 170 °C, on a glass build plate at 80 °C with Magigoo PP adhesive. A water uptake test on TPO reported a mass gain plateau of 0.25%, which is significantly lower than that of TPU, which suggests that TPO may not require drying before 3D printing. Tensile testing on FGF TPO specimens achieved similar stress at yield as well as stress and strain at break as indicated by the data sheet for the XY and YZ orientations. The Z direction is significantly weaker than the X and Y orientations, reaching only 30% of the stress at break. TPO achieved the best average stress at yield of 6.36 MPa using the 0.4 mm nozzle with XY printing orientation and stress and strain at break of 13.8 MPa and 1300% at YZ orientation and 1 mm nozzle. The setup achieved relatively high-quality prints of complex geometries, including the popular torture-test Benchy and a child-sized orthotic insole.

Ozerskoi, N. E.; Razumov, N. G.; Silin, A. O.; Zotov, O. G.; Borisov, E. V.; Popovich, A. A.

doi: 10.1007/s40964-024-00697-8pmid: N/A

Additive manufacturing is the manufacture of products with a shape close to a given shape, in which any part with a complex geometry is made by layer-by-layer melting of powder material using the energy of a laser or electron beam. CoCrFeNiMnWx high-entropy alloys are a promising material as a raw material used in additive manufacturing. In this work, three different compositions of CoCrFeNiMnWx (x = 0, 0.125, 0.25) high-entropy alloys powder were obtained by mechanical alloying and plasma spheroidization processes. Compact samples were fabricated by L-PBF method. Tests of mechanical characteristics in the temperature ranged from − 196 to 600 °C showed practical invariability of fracture energy both at cryogenic and high temperatures. When W was added to the alloy in the amount of 0.125 and 0.25 formula units, the tensile strength increased on average by 9 and 19%, and the yield strength by 10 and 18%, respectively. When tested at liquid nitrogen temperature, it is found that the yield and strength limits increase by 30–35% while maintaining ductility.

Santos, S.; Matos, C.; Duarte, I.; Olhero, S. M.; Miranda, G.

doi: 10.1007/s40964-024-00698-7pmid: N/A

Triply Periodic Minimal Surface (TPMS)-based aluminium–alumina Interpenetrating Phase Composites (IPCs) manufactured through the combination of Additive Manufacturing (AM) and investment casting are explored in this study. Multiple alumina TPMS structures (Gyroid, Diamond, and Primitive) with different geometries and volume fractions were designed and fabricated using Digital Light Processing (DLP) AM technology. Afterwards, these ceramic structures were filled with an aluminium alloy via investment casting, uncovering an aluminium–alumina IPCs. A global characterization was performed, including ceramics shrinkage and mass loss; specimens’ morphology; chemical and crystalline characterization; density analysis and mechanical testing. Overall, DLP technology was found effective for producing these highly complex ceramic structures, with high surface quality. The sintered alumina structures presented a relative density of ca. 76.3% and a pseudo-ductile layer-by-layer failure behaviour, with Diamond-based TPMS exhibiting the highest compressive strength. Regarding the IPCs, the addition of aluminium significantly changed the compressive behaviour of the samples, presenting an energy absorption behaviour. The integration of the alumina phase into the aluminium alloy led to an improvement on the compressive offset stress of approximately 6% when compared to the aluminium alloy used. Diamond and Gyroid IPCs demonstrated similar mechanical behaviour and the highest mechanical performance.Graphical Abstract[graphic not available: see fulltext]