Overmoulding of Plane Structural Foamed Parts with a Second Thermoplastic Component

Abstract

Over the last few years some highly-efficient manufacturing processes in the field of foam injection moulding occurred based on new developments in the machine, the mould and the material technology. The manufacturing of car interior parts with a soft touch surface for example became possible in a one-step injection moulding process, in which an injection moulded carrier made of a fibre reinforced thermoplastics is overmoulded with a foamed thermoplastic elastomer (TPE). The TPEcomponent with compact skin layers and a foamed core generates a soft touch effect, reduces the part weight and observes the quality standards of the automobile manufacturers. Furthermore this technique offers a much higher economic efficiency compared to conventional manufacturing processes. To lower the part weight even further it is aspired to produce the thermoplastic carrier in a physical or chemical foam injection moulding process. With special mould technologies and the right process management it is already possible to foam light plane parts with a high specific flexural stiffness. As the main function of the carrier is the stiffening of the part an interesting aspect is to combine a stiff foamed carrier with a soft TPE-component by an overmoulding injection moulding process. This paper is going to show the possibility to overmould a plane foam injection moulded part with a second thermoplastic component, e.g. a TPE. The aim is to reach ideal dimensional stability and mechanical properties by the right adjustment of the manufacturing process.