Additive manufacturing of polymers and composites for sustainable engineering applications

Two types of additive manufacturing (AM) techniques, fused filament fabrication (FFF) and selective laser sintering (SLS), were employed to fabricate specimens from three widely used AM polymers: polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), and polyamide (PA): the first two using FFF and PA using SLS. The single‐edge notch bending (SENB) test was employed to measure the mode‐I fracture toughnesses of bulk and AM specimens in three directions relative to the printing direction. Unlike their bulk counterparts, AM polymers exhibited anisotropic fracture toughness. The degree of anisotropy in FFF‐PLA was much larger than FFF‐ABS and SLS‐PA. The smallest fracture toughness value for each AM polymer was achieved along the transverse printing direction. Different AM techniques affect fracture toughness differently. For instance, FFF is shown to increase PLA's plastic deformation, while SLS reduces PA's ductility. The decrease in fracture toughness is consistently observed when transitioning from bulk polymers to AM ones, reaching as much as 75%. This study provides insights into the fracture toughness of AM parts made via popular plastics, which are crucial for designing structural parts using FFF and SLS processes.

Additive manufacturing (AM), commonly known as 3D printing, is an emerging technology with immense potential across various industries, particularly in the automotive sector. It involves the layer-by-layer fabrication of parts by gradually depositing material, distinguishing itself from traditional manufacturing through various ways, including design flexibility, reduced material wastage, shorter lead time, and the absence of tooling requirements. It is still in its nascent phase, and several drawbacks, such as a lack of mechanical strength, limited material availability, and poor surface finish, still hinder its integration into the mainstream production workflow. As a result, further exploration is required to harness its potential along with traditional methods. The automotive sector is long known for its adoption of cutting-edge technologies. Due to the vast potential of AM, the automotive industry is actively trying to incorporate additive manufacturing into mainstream production processes. Consequently, the automotive industry continuously explores ways to enhance this process for seamless integration into product development. However, research elucidating different additive manufacturing processes used within the automotive industry, such as stereolithography (SLA), fused deposition modeling (FDM), and selective laser sintering (SLS), is limited. This paper aims to illuminate various additive manufacturing processes used by automotive companies worldwide. In addition to exploring different processes, the study delves into the advantages and limitations of additive manufacturing, contributing to a comprehensive understanding of its application in the automotive manufacturing landscape. JEL Classification Codes: Y90.

3D printing, also known as additive manufacturing (AM), represents a rapidly evolving technological field capable of creating distinctive products with nearly any irregular shape, often unattainable using traditional techniques. Currently, the focus in 3D printing extends beyond polymer and metal structural materials, garnering increased attention towards functional materials. This review conducts an analysis of published data concerning the 3D printing of magnetic materials. The paper provides a concise overview of key AM technologies, encompassing vat photopolymerization, selective laser sintering, binder jetting, fused deposition modeling, direct ink writing, electron beam melting, directed energy deposition and laser powder bed fusion. Additionally, it covers magnetic materials currently utilized in AM, including hard magnetic Nd–Fe–B and Sm–Co alloys, hard and soft magnetic ferrites, and soft magnetic alloys such as permalloys and elect­rical steels. Presently, materials produced through 3D printing exhibit properties that often fall short compared to their counterparts fabricated using conventional methods. However, the distinct advantages of 3D printing, such as the fabrication of intricately shaped individual parts and reduced material wastage, are noteworthy. Efforts are underway to enhance the material properties. In specific instances, such as the application of metal-polymer composites, the magnetic properties of 3D-printed products generally align with those of traditional analogs. The review further delves into the primary fields where 3D printing of magnetic products finds application. Notably, it highlights promising areas, including the production of responsive soft robots with increased freedom of movement and magnets featu­ring optimized topology for generating highly homogeneous magnetic fields. Furthermore, the paper addresses the key challenges associated with 3D printing of magnetic products, offering potential approaches to mitigate them.

Due to geometrical degrees of freedom, low cost, and ease of realizing complex structures, polymer additive manufacturing (AM) has emerged exceptionally well. Even with rapid evolutionary growth, AM lacks sound quality mainly including inherent porosity and surface roughness compared to their counterparts (conventional manufacturing processes) due to the involvement of several printing parameters in AM processes. This quality‐based comparative assessment presents the influence of build/layer height on the porosity (using micro‐X‐ray computed tomography) and surface roughness (in build direction) of additively manufactured thermoplastic polyurethane (due to its versatile properties in applications like wearable electronics and biomedical) using three different polymer AM processes namely selective laser sintering, fused deposition modeling, and stereolithography. Along with porosity, an in‐depth pore characterization is also performed to understand the geometrical feature and severity of pores present in each sample of the AM process. Results are compared finally to make concluding remarks.

3D Printing and Industrial Ecology

Nowadays, additive manufacturing (AM) represents a pillar of Industry 4.0 that specifically addresses deep smart technology automation. In this context, the skills of additive manufacturing can be successfully exploited for efficient information technology integration and for increasing industrial economic competitiveness. The significant progress achieved in the last 10 years was obtained also because of the possibility of designing new materials systems specifically devoted to each AM process; in particular, a significant contribution has come from the new polymer-based systems, implemented for such specific additive manufacturing technologies as fused deposition modeling, selective laser sintering, stereolithography, and 3D inkjet printing processes. This chapter aims to provide the reader with an overall view of the main recent outcomes concerning the use of polymer-based materials for AM technologies, discussing the current limitations, and highlighting some perspectives for the near future.

Purpose – The purpose of this study is to compare the environmental impacts of two additive manufacturing machines to a traditional computer numerical control (CNC) milling machine to determine which method is the most sustainable. Design/methodology/approach – A life-cycle assessment (LCA) was performed, comparing a Haas VF0 CNC mill to two methods of additive manufacturing: a Dimension 1200BST FDM and an Objet Connex 350 “inkjet”/“polyjet”. The LCA’s functional unit was the manufacturing of two specific parts in acrylonitrile butadiene styrene (ABS) plastic or similar polymer, as required by the machines. The scope was cradle to grave, including embodied impacts, transportation, energy used during manufacturing, energy used while idling and in standby, material used in final parts, waste material generated, cutting fluid for CNC, and disposal. Several scenarios were considered, all scored using the ReCiPe Endpoint H and IMPACT 2002+ methodologies. Findings – Results showed that the sustainability of additive manufacturing vs CNC machining depends primarily on the per cent utilization of each machine. Higher utilization both reduces idling energy use and amortizes the embodied impacts of each machine. For both three-dimensional (3D) printers, electricity use is always the dominant impact, but for CNC at maximum utilization, material waste became dominant, and cutting fluid was roughly on par with electricity use. At both high and low utilization, the fused deposition modeling (FDM) machine had the lowest ecological impacts per part. The inkjet machine sometimes performed better and sometimes worse than CNC, depending on idle time/energy and on process parameters. Research limitations/implications – The study only compared additive manufacturing in plastic, and did not include other additive manufacturing technologies, such as selective laser sintering or stereolithography. It also does not include post-processing that might bring the surface finish of FDM parts up to the quality of inkjet or CNC parts. Practical implications – Designers and engineers seeking to minimize the environmental impacts of their prototypes should share high-utilization machines, and are advised to use FDM machines over CNC mills or polyjet machines if they provide sufficient quality of surface finish. Originality/value – This is the first paper quantitatively comparing the environmental impacts of additive manufacturing with traditional machining. It also provides a more comprehensive measurement of environmental impacts than most studies of either milling or additive manufacturing alone – it includes not merely CO2 emissions or waste but also acidification, eutrophication, human toxicity, ecotoxicity and other impact categories. Designers, engineers and job shop managers may use the results to guide sourcing or purchasing decisions related to rapid prototyping.

Impact behavior and fractography of additively manufactured polymers: Laser sintering, multijet fusion, and hot lithography

Dimensional accuracy of additively manufactured structures for modular coil windings of stellarators

Additive Manufacturing (AM) is a well-known technology, first patented in 1984 by the French scientist Alain Le Mehaute [...]

Institutional support can play an important role in supplementing private investment in innovative activities, especially in latecomer countries. This prospect can be particularly challenging in nations not leading the technological frontier, which suffer from higher resource scarcity than technology leaders. We study the case of the adoption of polymer (PAM) and metal (MAM) additive manufacturing technologies in the Portuguese molds industry, both of which offer important benefits for competitiveness. Leveraging archival data (about the history of Portugal and the technologies); insights from 45 interviews across academia, industry, and government; and 75 hours of participant observations, we develop insights about why institutional instability in Portugal affected the adoption of Polymer Additive Manufacturing (PAM) and Metal Additive Manufacturing (MAM) differently. In both cases, Portugal invested in the technology relatively early. While PAM has been widely adopted, including increasingly in high-tech applications, MAM adoption has been modest despite MAM’s potential to greatly improve the performance and competitiveness of metal molds. From the comparison between PAM and MAM, we generate theory about technological and contextual factors that affect ‘technological forgiveness’, defined as the resilience of a new technology’s adoption to institutional instability. We conclude by proposing a generalizable framework for ‘forgiveness’ in different industrial contexts.

The use of computer-aided design/computer-aided manufacturing (CAD/CAM) and additive manufacturing in maxillofacial prosthetics has been widely acknowledged. Rapid prototyping can be considered for manufacturing of auricular prostheses. Therefore, so-called prostheses replicas can be fabricated by digital means. The objective of this study was to identify a superior additive manufacturing method to fabricate auricular prosthesis replicas (APRs) within a digital workflow. Auricles of 23 healthy subjects (mean age of 37.8 years) were measured in vivo with respect to an anthropometrical protocol. Landmarks were volumized with fiducial balls for 3D scanning using a handheld structured light scanner. The 3D CAD dataset was postprocessed, and the same anthropometrical measurements were made in the CAD software with the digital lineal. Each CAD dataset was materialized using fused deposition modeling (FDM), selective laser sintering (SLS), and stereolithography (SL), constituting 53 APR samples. All distances between the landmarks were measured on the APRs. After the determination of the measurement error within the five data groups (in vivo, CAD, FDM, SLS, and SL), the mean values were compared using matched pairs method. To this, the in vivo and CAD dataset were set as references. Finally, the surface structure of the APRs was qualitatively evaluated with stereomicroscopy and profilometry to ascertain the level of skin detail reproduction. The anthropometrical approach showed drawbacks in measuring the protrusion of the ear's helix. The measurement error within all groups of measurements was calculated between 0.20 and 0.28 mm, implying a high reproducibility. The lowest mean differences of 53 produced APRs were found in FDM (0.43%) followed by SLS (0.54%) and SL (0.59%)--compared to in vivo, and again in FDM (0.20%) followed by SL (0.36%) and SLS (0.39%)--compared to CAD. None of these values exceed the threshold of clinical relevance (1.5%); however, the qualitative evaluation revealed slight shortcomings in skin reproduction for all methods: reproduction of skin details exceeding 0.192 mm in depth was feasible. FDM showed the superior dimensional accuracy and best skin surface reproduction. Moreover, digital acquisition and CAD postprocessing seem to play a more important role in the outcome than the additive manufacturing method used.

Roadmap to sustainable plastic additive manufacturing

Purpose – The purpose of this paper is to compare four different additive manufacturing (AM) processes to assess their suitability in the context of upper extremity splinting. Design/methodology/approach – This paper describes the design characteristics and subsequent fabrication of six different wrist splints using four different AM processes: laser sintering (LS), fused deposition modelling (FDM), stereolithography (SLA) and polyjet material jetting via Objet Connex. The suitability of each process was then compared against competing designs and processes from traditional splinting. The splints were created using a digital design workflow that combined recognised clinical best practice with design for AM principles. Findings – Research concluded that, based on currently available technology, FDM was considered the least suitable AM process for upper extremity splinting. LS, SLA and material jetting show promise for future applications, but further research and development into AM processes, materials and splint design optimisation is required if the full potential is to be realised. Originality/value – Unlike previous work that has applied AM processes to replicate traditional splint designs, the splints described are based on a digital design for AM workflow, incorporating novel features and physical properties not previously possible in clinical splinting. The benefits of AM for customised splint fabrication have been summarised. A range of AM processes have also been evaluated for splinting, exposing the limitations of existing technology, demonstrating novel and advantageous design features and opportunities for future research.

Additive manufacturing technology is the process in which material is manufactured using different additive processes. There are many additive processes such as Stereo lithography (SLA), Selective laser sintering (SLS), Fused deposition modeling (FDM), etc. FDM is most popular additive manufacturing process in which parts are manufactured in layers. Among all additive manufacturing technology, FDM process is the most versatile additive manufacturing process due to low cost, flexibility, broad range in material, low time consumption and accessibility. FDM process is the most economical process compare to other additive manufacturing processes. A study of wettability is basically depending on the process parameter such as layer thickness, build orientation, print speed and post processing method. In this research work, wettability of 3D printed PLA parts have been investigated at different raster angles.Additive manufacturing technology is the process in which material is manufactured using different additive processes. There are many additive processes such as Stereo lithography (SLA), Selective laser sintering (SLS), Fused deposition modeling (FDM), etc. FDM is most popular additive manufacturing process in which parts are manufactured in layers. Among all additive manufacturing technology, FDM process is the most versatile additive manufacturing process due to low cost, flexibility, broad range in material, low time consumption and accessibility. FDM process is the most economical process compare to other additive manufacturing processes. A study of wettability is basically depending on the process parameter such as layer thickness, build orientation, print speed and post processing method. In this research work, wettability of 3D printed PLA parts have been investigated at different raster angles.