Powder bed fusion for electromechanical plastic components in high voltage electric vehicle applications.

Abstract

Over the years, Injection Molding has been the ruling process to manufacture polymeric components for the automotive industry. By this process, excellent properties and fully dense parts can be achieved. Injection Molding can be pricey if a production batch size is not big enough to justify the high costs of the molds. With the increasing demand for Electric Vehicles, the need for plastic parts with a combination of good mechanical and dielectric properties could grow significantly. When low production volumes are required, Additive Manufacturing of polymeric components can be considered as an alternative to Injection Molding. For this to happen, the behavior of parts produced by Additive Manufacturing need to be tested in order to demonstrate their mechanical capabilities and as electrical insulators within a high voltage level, at which components and devices utilized in Electric Vehicle applications are tested.

In this work, tensile and electrical insulation specimens manufactured from polyamide (PA12) by Selective Laser Sintering (SLS) and HP- Multi Jet Fusion (MJF) in three build orientations were tested and compared to equivalent specimens produced by Injection Molding. For analyzing their mechanical properties, tensile tests were carried out according to the ISO-527 standard. To evaluate their efficiency as electrical insulators, voltage withstand (HIPOT) tests were performed to the specimens at a voltage level of 4kV AC and within a temperature range between 20 and 100°C.

The test results obtained by the tensile experiments denoted that the parts produced by Powder Bed Fusion for these experiments presented brittle behavior at fracture, with a maximum elongation at break between 10-26%. The maximum achieved tensile strength values represented almost 74% of the ones obtained by the injection molded equivalent specimens. As electrical insulators, the HIPOT test results showed that SLS specimens with a thickness of 2mm withstood a 4kV AC voltage load comparably as the injection molded parts. The Radiation- Absorbing Material present in the HP-MJF fusing agent could be a contributor for dielectric breakdown on the tested specimens. Therefore, the applicability of the HP-MJF process is questionable for high voltage environments and within the test conditions employed.