Metal Injection Moulding - Case Study, A Stainless Steel Gas Connector Flange

Background

Metal injection moulding (MIM) is an advanced manufacturing process for the net shape forming of small, complex, high-precision and high performance metal parts. It is a development of the traditional powder metallurgy (PM) process and has several key advantages.

Advantages of Metal Injection Moulding Over Traditional Powder Metallurgy

In the PM process, parts with undercuts or projections at right angles to the pressing direction cannot normally be directly made. The MIM process substantially removes this limitation. Full density components can also be realised with MIM.

An Overview of the Metal Injection Moulding Process

Injection moulding is well established for producing quite intricate parts in plastic. Adapting this process for metals involves mixing a very high volume of metal powder with organic binders to produce a feedstock with toothpaste-like consistency. A bonded metal ‘green’ part is then moulded. Careful removal of the binders leaves a skeleton of metal which is then subjected to high temperature sintering. After sintering, full density can be realised and for that reason the mechanical properties of MIM components are generally superior to those of traditional PM parts. MIM components have properties similar to wrought materials and dimensional tolerances superior to investment casting.

Materials Suitability for Metal Injection Moulding

Almost any metal that can be produced in a suitable powder form can be processed by MIM. The list of metals useable in MIM includes many common, and several less common metals and their alloys - plain and low alloy steels, high-speed steels, stainless steels, superalloys, intermetallics, magnetic alloys, controlled expansion alloys and hard metals (cemented carbides). Clearly, where the net shape forming capability of MIM is combined with the application of expensive materials then the advantages of MIM multiply. This is because, unlike alternative processes that involve machining, metal yield in MIM is very high and there is practically no wastage.

Case Study – Stainless Steel Gas Connector Flange

A good example of MIM’s advantages is illustrated by a manufacturer who had a fabrication problem. He had a sub-assembly that was comprised of three separate parts. Previously these were machined separately from wrought stainless steel and vacuum brazed together - the problem was high cost and poor quality. Using MIM, the part was re-engineered into one moulding and in doing so realised significant cost savings as well as improvements in quality.

Primary author: David Power

Source: Abstracted from Materials World Vol. 10. no. 7, pg. 23 July 2002.

For more information on this source please visit The Institute of Materials, Minerals and Mining.