Low Pressure Powder Injection Moulding of Metals, Ceramics and Metal Matrix Composites

Background

Powder injection moulding (PIM) uses sinterable powders to manufacture very intricate components. Unlike traditional press-and-sinter powder metallurgy processes, PIM could potentially allow the economic mass production of dense, net-shaped metal, ceramic and cermet components. These ran be geometrically intricate and be produced to close dimensional tolerance.

Low Pressure Powder Injection Moulding

Low pressure injection moulding is a variation on PIM, and vairies in that materials can be injected into the mould at low pressures. Low viscosity compositions can be made from wax-based binders, and these can be easily processed at low injection pressures.

Advantages of Low Pressure Powder Injection Moulding

Low pressure moulding offers significant processing advantages compared to high pressure PIM technology based on thermoplastic resins. Considerable cost savings can be made in component production as the machine and the moulds are lighter and less costly. This makes manufacturing small numbers of particular components economical, because the machine and mould costs are less significant than with high pressure technology. Moulds for low pressure processing are generally made from aluminium. RheoTech has also used filled epoxy moulds as well as moulds produced by stereolithography for prototyping. Other benefits of low pressure processing are:

•         Reduced anisotropy in moulded components

•         Lower energy requirements

•         Reduced machine and mould wear

•         Lower mould costs

•         Reduced processing equipment costs

•         Increased flow path

•         More complex geometries – thinner wall sections

•         Larger components

•         Wider component design capability

The most significant advantage of low pressure processing is the ability to make large mouldings. Low viscosity compositions do not need such a robust mould as high pressure/high viscosity PIM systems. As a result, a wide range of product sizes is possible using low pressure injection moulding. Component size and mass range from 100μm to lm in length and from 0.1g to 50kg, with a tolerance of better than +/-0.15% in a given dimension.

Primary author: Dr. Michael Martin

Source: Materials World Vol. 7 no. 2, pp. 71-75 February 1999.

For more information on this source please visit The Institute of Materials.