Large scale additive manufacturing of foamed structures using thermally expandable microspheres

Abstract This paper presents investigations into the additive manufacturing of foamed plastics. This includes granule-based material extrusion (MEX) of thermoplastic elastomers (TPE) with thermally expandable microspheres (TEM). The process used can be classified as large-scale additive manufacturing (LSAM). Investigations are carried out on the influence of the parameters extruder rotational speed n and feed rate $$\:\overrightarrow{{v}_{F}}$$ on the formation of the strand geometry for different TEM contents. Process windows for specific strand geometries are then derived from the results and test specimens are produced. These test specimens are used to examine properties such as Shore hardness, density and mechanical strength as a function of TEM content. During the investigations, the highest density reduction of over 50% was achieved with a TEM content of 3 wt%. This article presents a scientific examination of the large-scale additive manufacturing of foamed structures from TPE. The process windows determined form the basis for further investigations into the transfer of the process to real applications, for example in the packaging industry.