Fused granulate fabrication of injection molding inserts from high-performance ULTEM 9085™ thermoplastic for cosmetic packaging industry

Abstract

RTIM refers to the integration of rapid tooling (RT) using additive manufacturing (AM) with injection molding (IM). Due to the use of raw material (pellet), screw extrusion, fused granulate fabrication (FGF) allows for a cost-effective and versatile production of RTIM inserts especially compared to other material extrusion (MEX) AM processes, such as fused filament fabrication (FFF). This study 3D printed RTIM inserts out of high-performance thermoplastic polyetherimide (PEI) (ULTEM 9085) in granular form, using an in-house developed FGF system. A cosmetic compact was used as a case study part with a simplified design. A dynamic mechanical analysis (DMA) conducted on FGF ULTEM 9085 demonstrated that the strength of the inserts is sustained up to 140 °C, which suits injection molding using polypropylene (PP). Optical profilometry of the FGF 3D printed RTIM inserts demonstrated that when using a 0.4 mm nozzle, the flat surfaces produced had microscopic gaps larger than 10–1 mm. These gaps are sufficiently large so that melt of low viscosity polymer is able to flow through, which leads to undesired part flash. The IM experiments confirmed that the inserts were capable of producing PP parts but with the predicted flash. Simulated part deflection differed both on geometry and magnitude from the actual deflection measured by optical profilometry. A total of 36 prototype parts were produced before the inserts failed due to poor inter-layer bond strength. FGF RTIM using ULTEM 9085 is deemed suitable for prototype part production. Improving the inter-layer bond strength and decreasing part complexity could increase the number of parts produced.