Feature article: PIM International, Vol.4 No.1 March 2010, pages 21-27, 3465 words

Author: Dr. - Ing. Frank Petzoldt, Fraunhofer IFAM, Germany

Powder Technology Department, Fraunhofer IFAM, Wiener Straße 12, 28359 Bremen, Germany

The ability to manufacture components in one step using two different materials is opening up a world of opportunities for the powder injection moulding industry. The possibilities range from combining metals with different properties through to metal/ceramic and ceramic/ceramic components. Dr. Frank Petzoldt looks at the development of this technology to-date and outlines the challenges that need to considered when planning a two-component PIM part

Plastic components with a multi-material design are widely used in our daily lives and two-component plastic injection moulding technology is a well known and economical series production process. In the plastics industry, it enables the use of the same material in different colours in a product, or two different materials in the same or in different colours within one product. Examples of common multi-part / multi-colour products for everyday use or technical applications include:

• tooth brushes
• toys
• food packaging
• electrical equipment
• engineering components

With two-component injection moulding, moulded components composed of several parts or colours are produced on a single machine. It is, therefore, an economical production process avoiding further handling and assembly. Two-component injection moulding is the process of feeding two different melts, one after the other, into the same mould. The melts should make contact with each other but should not flow into each other.

Usually, a pre-moulded part is produced from the first material in an initial process step, which is then combined with the other material. As interest in ceramic and metal multi-functional components has grown, so new economic manufacturing processes have needed to be developed.

Once powder injection moulding was established as a mature technology the natural next step was to look for further opportunities to broaden the scope of the technology. Two major trends emerged: miniaturisation and multi-functionality........

Further sections of this article include:

The advantage of powder injection moulding
Two-component injection moulding
The 2C-PIM process
Prediction of feasible material combinations
Simulation
Advancing the process
Case Studies
- Magnetic/Non-Magnetic
- Ceramic/Ceramic
- Metal / Ceramic
Conclusion
Acknowledgements
Literature

Figures and Tables:

Fig. 1 An ALLROUNDER 370 S 700-70 2 colour injection moulding machine from Arburg

Fig. 2 Apparent Co-Sintering Index (ACSI) for five different magnetic/non-magnetic material combinations. Combinations 3, 4 and 5 with an ACSI of <15 would be feasible

Fig. 3 SIGMASOFT simulation of simultaneously injected magnetic/non-magnetic materials into a 2C-MIM tensile bar

Fig. 4 Comparison of SIGMASOFT simulation and microscopic analysis of the contact zone (sliced view)

Fig. 5 Magnetic micro positioning encoder

Fig. 6 Magnetic micro tachometer made of 316L and 17-4 PH stainless steels

Fig. 7 Heater plug green parts and testing of the sintered parts (inset) (Courtesy Fraunhofer IKTS)

Fig. 8 An example of a two-component CIM component. This CIM gear wheel combines alumina and zirconia toughened alumina (Courtesy Fraunhofer IKTS, designed by Robert Bosch GmbH)

Fig. 9 CAD drawing of the bipolar surgical grasper, stainless steel (blue) and ceramic protective coating (grey) (© Olympus, Winter & Ibe)