Additive Manufacturing (AM) or 3D printing is a manufacturing technique where successive layers of material are layered to produce parts. The design freedom afforded by AM is ideal for the space industry, where part production is low volume and highly customized. The objective of this paper is to review research in the area of Additive Manufacturing For Space (AMFS) in all areas, from propulsion to electronics to printing of habitats, and to identify the gaps and directions in the research. In this paper we investigate the AMFS research by splitting it into two domains: space and ground-based. Space-based AMFS has been performed on the International Space Station using polymers and we also discuss the future of in-space AM, a subject closely related to more general in-space manufacturing. The ground-based research is split into three categories based on the printing material: metal, polymer, and other. The last category includes regolith, cement, and ceramic. This paper explores AMFS by bringing together as much research information as possible using a combination of papers, presentations, and news articles. We expect that the paper will allow the reader to gain an understanding of the current status of AMFS research and will contribute to the field as a reference and research guidelines.

Purpose Springs are an integral part of mechanisms and can benefit from additive manufacturing’s (AM) increased design freedom. Given the limited literature on the subject, the purpose of this paper is to develop guidelines for fabricating helical springs using three-dimensional (3D) printing. Design/methodology/approach Polylactic acid (PLA) is the main material investigated, with ULTEM™ 9085 used as a comparison. The experimental procedure is to vary the spring parameters, print the springs and test them in tension or compression using constant velocity. Plots of the force and displacement are used to measure the linear and post-deformation spring constants. Loading of the springs is done both to breakage and cyclically. Cyclic loading is also used to observe the plastic behaviour of the springs. Parameters that are varied include wire and coil diameters, pitch, wire cross-section, in-fill and layer height. Findings A square wire cross-section is used, instead of a circle because it produces more consistent coils. In-fills make no significant difference in the elastic stiffness of the springs but the mono in-fill breaks at a greater extension, so it is recommended. Tension and compression springs are confirmed to behave the same when in the elastic regime. ULTEM™ 9085 produces consistently weaker springs compared to PLA. Variation of layer height shows that thinner layers increase the stiffness of the springs. Originality/value This study investigates the behaviour of 3D printed helical springs in tension and compression. Three guidelines are created: square wire cross-section, mono-directional in-fill and thin layers are recommended.

The helical spring is one of the most used components in mechanisms but there is little research on the application of 3D printing, also called Additive Manufacturing, to springs. Therefore, the objective of this paper is to derive a model for the stiffness of 3D printed springs. The equation assumes that springs are made of orthotropic material and with a rectangular wire cross-section, that is, die springs. A second version of the equation has also been postulated that accounts for the misalignment of the deposited tracks with respect to the direction of the coils due to the coil pitch. The two models are compared to various springs printed with PLA and ULTEM 9085 and are found to accurately predict the stiffness of real, 3D printed springs. These equations allow the design and manufacturing of helical die springs for applications with few load cycles and that require chemical and radiation resistance, such as in space. The equations are also the first step in the development of models for new kinds of springs, such as linear conical springs or hollow wire die springs.