Process analysis of foam injection moulding with physical blowing agents

Walter Michaeli, Axel Cramer

Institute of Plastics Processing at RWTH Aachen University

Pontstraße 49, 52062 Aachen, Germany

1 Abstract

Through the application of structural foam injection moulding it is possible to reduce cycle time and thereby to attain economic benefits compared with conventional injection moulding. The highest savings potential is offered by the cooling phase. To determine possible savings, the surface temperature distribution of the parts produced was measured by infrared thermography after identical cooling times of compact and foamed parts. The cooling time was then shortened at selected test points to the minimum necessary for stable demoulding. A direct comparison between compact and foamed parts shows that, for a filled polypropylene, a cooling time reduction of up to 25 % is possible with a wall thickness of 4 mm. An influence of the process parameters and geometric boundary conditions was also established. The causes of these phenomena are analysed and discussed in detail.