Powder Injection Moulding - An Alternative Processing Method for Automotive Items

Abstract

Powder injection moulding (PIM) technology represents a challenging production method for automotive items, alternative to machining and investment casting. The European automotive industry utilizes PIM applications over 50% of the time (Kearns, 2009). In Germany the first Schunk penetrations into the automotive industry were lock caps and lock shafts, followed by cable seals used to fix the cable to car sunroofs, soft magnetic sensor housing parts, cams for electrical adjustment mechanism of car seats, bonnet lock fixing bearings, or rocker arms for VVT engines used by BMW, produced now at an annual rate of 4.5 million pieces. Nowadays, even more stringent parts such as turbocharger vanes, rollers and adjustment rings are produced there (Schlieper, 2007). Concerning ceramics, good application examples are the 8-inch-diameter turbine wheels produced by General Motors for a turbine engine and large static components for automotive gas turbine programs (Moritz & Lenk, 2009). Recently, a HYDRO-PIM project in Austria was aimed at developing potential applications for PIM stainless steel for use in extreme low temperatures for BMW Hydrogen 7 (anonym, 2007). Another European project, CarCIM, was initiated in 2006 to develop ceramic components for automotive and railway applications – glow plug, gear wheel, a valve set and braking pads using two-component PIM (Moritz, 2008). Fraunhofer IFAM has coordinated a European project dealing with new material laws for PIM feedstocks called MATLAW to improve feedstock’s characteristics and mould filling simulation approaches (Williams, 2009). Although PIM technology was first commercialized in North America, nowadays Asia is the largest market. The automotive sector remains the largest (19.9 %) user of PIM parts in Japan (anonym, 2010). The earliest application of PIM in China was an alumina spark plug body for automobile engines in the 1960s (Li, 2007). During the PIM process, a powder must be at first compounded with a suitable polymer binder to obtain a highly (typically around 60 vol. %) concentrated compound, which is then processed in injection moulding machines utilized in the plastics industry. In the next step, a binder is chemically or thermally withdrawn from the moulded (green) part, and the remaining purely metal or ceramic (brown) part is sintered to its final dimensions and density. PIM is clearly an interdisciplinary technique combining metallurgy with the processing of plastics. Therefore, products made with PIM technology take advantage of the material