A sectioning method for constructing the mid-surface of thin-walled die-cast and injection moulded parts

Rapport, 2006

This report presents a method for constructing the mid-surface of CAD-models of parts requiring tooling for their manufacture. The mid-surface is constructed by sectioning the CAD-model in a sufficient number of places along the draft direction. In each section the mid-segments of the sectioned material is constructed. The complete mid-surface is obtained by connecting the individual mid-segments with the closest located mid-segment in the adjacent sections. The intended use of the method is computer implementation to automatically derive the mid-surface from CAD-models to be used as target geometry for FEA shell element meshing. The feasibility of the method is demonstrated by applying it to a CAD-model. In this example a target surface is constructed using both the conventional and the sectioning method. The target surfaces are used to create shell element FEA models. When solved, the natural frequencies of the two models are almost the same. This shows that the sectioning method is an alternative way of creating the target geometry. The intention is to use the method to create an automatic tool for mid-surface extraction with better performance than today’s commercially available tools.