Development of an innovative micro extrusion head based on screw for experimental additive manufacturing machines

The purpose of this work is to present the design planning and development of a screw extrusion head with variable section screw. The conceptual validation was performed in a portable open-source additive manufacturing machine (Fab@CTI machine). It was made a pre-calculation of the main components of the head, which were: screw, barrel and transmission system. The materials considered for the theoretical calculations were Nylon® 12 and the biopolymer ε-PCL (ε-policaprolactone) in powder form. The screw extrusion head was manufactured and assembled demonstrating the functionality to carry the powder material through the sections of the screw extrusion and generated Nylon® 12 filaments with diameter of approximately 0.7 mm using a tip of diameter 0.4 mm. The morphological characteristics of the filaments were observed in Scanning Electron Microscopy (SEM) confirming the mixing of the powder, generating a continuous filament. SEM tests were made with ε-PCL using material generated from the feed zone and the compression zone of the screw extrusion head allowing the visualization of the adhesion of the grains in feed section and the complete mixing in the compression zone for the ε-PCL