Miniaturized fused granulate fabrication of polyether ether ketone (PEEK)

Abstract

This study demonstrates that a 4.25:1 length to diameter ratio (L:D) granulate screw extruder can be used for the fused granulate fabrication (FGF) of polyether ether ketone (PEEK) objects. PEEK is a biocompatible, high-performance thermoplastic with good mechanical, thermal and electrical properties. This study focused on fused granulate fabrication (FGF) which employs granulates rather than filament as the raw material, which enables great freedom in material selection at a much lower cost. The short L:D ratio screw developed and used allows for a smaller extruder than the ones found in literature. The extruder was calibrated for additive manufacturing at different speeds using a 1 mm nozzle. The results demonstrate that there is a non-linear relationship between screw speed and extrusion rate, therefore, to use fused filament fabrication systems (FFF) slicing software for FGF, the 3D printing speed for the whole printing cycle has to be kept constant. This study was conducted in an open chamber which resulted in an ultimate tensile/yield strength of 49 MPa which is around 48% of injection moulded PEEK as stated in the material datasheet. The quality of the prints was evaluated using optical profilometry which reported a surface roughness for top and side faces of 9.8 and 31 μm Ra, respectively. These results are similar to ones found in literature which used a 0.8 mm nozzle. This showed that FGF systems can be miniaturised even for additive manufacturing of high-temperature, high-viscous, high-performance polymers, such as PEEK.