Injection Moulding Asia

PIM technology sees its worth in India

This article by Christian Kniezanrek, Senior Sales Manager (China, Japan, Taiwan and South Korea) of Wittmann Battenfeld outlines the metal injection moulding technology that is used by Indian processor Indo-US MIM.

Powder injection moulding (PIM) is a process to produce injection moulded parts from metallic or ceramic compounds. It is used to produce complex geometries with high dimensional accuracy in large quantities and at low cost. With its special advantages of high precision and repeatability, this process is optimally suited for cost-efficient mass production.
           
Description of the process
Metal injection moulding (MIM) is one of two powder injection moulding (PIM) applications. The other is ceramic injection moulding (CIM). With the benefits of injection moulding, the use of PIM over mechanical forming processes lies in the fact that additional complexity of the manufactured parts does not cause any additional costs. It allows the implementation of an efficient manufacturing process with excellent tolerances for large quantities and/or technically advanced, complex parts (including micro parts).

Although the shrinkage in PIM is about 15-20% (depending on the binder content and the grit size distribution of the powder), it is still possible to produce high-precision filigree parts thanks to the high repeatability of this process. Moulds for the production of PIM parts must be manufactured according to special design guidelines and from wear-resistant tooling steel.

This allows the production of highly integrated components, which contributes to minimising the overall costs. This process even has an edge over precision casting, especially complex parts produced in large quantities and to high quality standards.

How the process works
The entire process consists of four steps. The first step is blending the powder with a binder to obtain the feedstock. The powder content is normally the maximum possible or close to the maximum, that is about 60 % of the total volume. Some parameters such as shrinkage can be influenced by varying the powder and the binder. Ready-mixed feedstocks are commercially available.

The second step is the production of moulded parts on an injection molding machine, a process similar to injection moulding of thermoplastic materials. The resulting parts are known as green parts.

The third step is the removal of the binder - normally by a thermal or chemo catalytic process - to obtain the brown parts. In the final step, these brown parts are sintered to produce the finished components.

Indo-US MIM
Wittmann Battenfeld has been one of the pioneers in developing this technology and has cooperated with market leader Indo-US MIM, based in Bangalore, India. Following its establishment in 2001, this processor soon developed into one of the most renowned metal injection moulders worldwide.

Indo-US MIM specialises in the production of highly complex precision parts and its main customer base is in the automotive, aviation, telecommunication and medical technology industries. With sales and service subsidiaries in Europe, America and Asia, Indo-US MIM offers worldwide customer support, from product design and construction to comprehensive after-sales service.

With more than 25,000 sq m of production floor, Indo-US MIM has the largest and most modern metal injection moulding facility worldwide. Its R&D department develops about 200 injection moulded parts every year.

It also has more than 40 injection moulding machines from Wittmann Battenfeld’s hydraulic HM series, with clamping forces ranging from 80 to 100 tonnes. Due to the company’s rapid growth, about 10 new machines are added each year.

Wittmann Battenfeld supplies customised plasticising systems and screws for PIM. Due to the special attributes of the feedstock used, the machines are fitted with the following special equipment:

• Barrels and screws made of highly wear-resistant materials. The material specification depends on the type of powder to be processed. A set of barrel and screw made of hard metal is necessary for processing hard metal powders
• Optimised screw geometry for processing metallic and ceramic compounds
• High injection speed for extra dimensional accuracy in forming the part geometry
• Temperature-controlled feed zone
• Special hopper
• Special ejector function with open safety gate
• SPC quality monitoring
• Customised automation as required