Applications for MIM II: The Automotive Industry
The automotive industry: A major consumer of MIM parts
The automotive sector has become a major consumer of MIM, and parts of high complexity are used in engines, gearboxes, turbochargers, locking mechanisms, steering systems and electronic systems, to name just a few.
Rocker Arms for BMW engines
An example is the roller following type rocker arm shown in Fig. 20. This rocker arm for engines with a variable valve stroke is made from low alloy steel. It features a hollow configuration, saving weight, which is difficult to achieve by other processes.
The variable valve lift enhances the engine performance and reduces fuel consumption. Around 4.5 millions parts are produced annually using a hardenable 50NiCrMo2.2 steel powder alloy.
This extremely high volume MIM component is part of a passenger car's manual transmission.
The component is shown in the various manufacturing stages: moulded, sintered, hardened, and assembled with a shaft.
The material is Fe-2% Ni. The part is case hardened after sintering.
This MIM variable nozzle vane is produced in very high volumes for automotive diesel turbochargers. The part meets strict dimensional tolerance requirements, as close as ±0.015mm on the wing profile, which was achieved with machining.
It is produced using a special tool that has a unique sliding function when opening, reducing deformation during ejection. MIM production offered a 20% cost saving.
The production of MIM superalloy components is now far advanced, with an ever increasing market share. Materials such as Inconel 713 are readily available as MIM feedstocks.
MIM processing, thanks to the finely dispersed powders used, delivers parts with a very homogeneous microstructure, which improves significantly on the microstructure of an investment cast product.