doi: 10.3850/978-981-11-0749-8_691
Effect of Residual Stress on the Distortion of Microembossed Metal Inserts for Assembly Injection Moulding
Philipp Frey, Christoph Höhler and Marion Merklein
Institute of Manufacturing Technology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) Egerlandstrasse 13, 91058 Erlangen, Germany
Abstract
The rising demand of electronic systems with functional density for industrial and automotive applications causes an increased need of media tight components, which are capable to withstand rough operating conditions. Those systems are typically manufactured by overmoulding blanked metal inserts within an assembly injection moulding process. In order to overcome the difficulties, caused by the incompatibility of polymer and metal, the application of grooved structure to metal insert by means of embossing is a favourable approach. However, the blanking and forming operations induce residual stresses into the workpiece. In the subsequent overmoulding step those metal inserts are exposed to elevated temperature which induces additional stresses on the one hand and can cause relaxation on the other hand. As a result, distortion of the inserts can occur which in turn affects the assembly injection moulding process and thus the properties of the final part in an undesirable way. Therefore, this study investigates the effect of blanking operations as well as the influence of different microembossed geometries on distortion of metal inserts in context of heat treatment for AlMg3 and CuSn6. Based on the results, no distinct effect of temperature gradient on the initial stress state of the unprocessed insert was observed. However, embossing of structures was discovered to change this effect and supports a distinct reaction to the temperature gradient.
Keywords: Residual stress, Microforming, Assembly injection moulding.
