Tough act

German researchers have modified conventional injection moulding techniques to produce small precision metal components — an impossible feat with traditional plastic injection moulding.

Injection moulding intricate parts in a number of plastic materials is a well-known and inexpensive form of production. However, for some engineering applications, thermo-plastic materials have inadequate mechanical properties. By incorporating a high-volume fraction of metal powder into a mix it is possible to create a plastic-bonded metal with highly desirable properties. 

Now researchers at the Fraunhofer Institute for Manufacturing and Advanced Materials (IFAM) in Bremen, have modified this variation to produce micromechanical components. The process works by mixing the metal powder with a binding agent; the paste-like mass is then injection moulded. In the second stage the component is gradually heated in an inert gas atmosphere, where the binding agent decomposes and escapes.

Then, at temperatures well below boiling point, the powder particles of metal sinter together and the component becomes compact, attaining up to 99 per cent of its maximum density. This makes the mechanical properties generally superior to those of traditional processes.