Wear-effects Induced by Powder Injection Molding of Zirconia Feedstocks

Powder injection molding (PIM) is a process for producing ceramic or metal parts, with complex geometries and in large scale production. The durability and quality of the mold is important because minor faults in shape and surface of the cavity can already lead to scrap production. The wear caused in PIM is significantly higher than the wear caused by plastic injection molding even though there are only a few specific papers dealing with this topic. The reason for this is often attributed to wear effects, caused by the ceramic or metal powder in the feedstock. As the higher wear in PIM shortens the tool life the understanding of the wear is of prime importance. Especially regarding to the commercial use a reduction of the wear effects during PIM is essential. In the following paper a method for recording data and characterizing the wear phenomena in the PIM process is developed. Mold inserts with exchangeable metal test structures for an existing mold have been designed and constructed for a systematic recording of the wear caused by PIM. The measurements have been performed for different numbers of injection cycles (0/500/1000/1400). The results show a significant reduction of the surface roughness on the examined surfaces of the brass test structures after 1400 injection cycles. A relation between shear rate and reduction of the surface roughness of the brass test structures could be found.