Additive Manufacturing of Soft and Composite Parts from Thermoplastic Elastomers

Thermoplastic elastomers (TPEs) are low-durometer materials that can support large strains without breaking, making them attractive materials for producing 3-D printed soft components. However, prefabricated TPE filament, especially those with low hardness, cannot be used in typical filament feed extrusion mechanisms that are popular in material extrusion-based 3-D printers today. Therefore, we have developed a mini-screw extruder, small enough to be incorporated on a typical 3-D printer system, and capable of extruding various TPE formulations directly from commercially available pellets. This paper presents the design and thermal analysis of the mini-extruder, experimental testing of the 3-D printing process for TPEs with nominal hardness in the range of 5 – 52 Shore A, and compression and tension tests of the properties of printed parts. By combining 3-D printing of soft TPEs with rigid thermoplastics, the new system also opens up new possibilities in additive manufacturing of soft and hard composite parts.