Influence of the Cutting Edge Geometry on the Tool Stress Distribution in Monocrystalline Silicon Punches for Microblanking of Thin Metal Foils

摘要

The continuous demand for metallic micro parts in high quality results in the need of appropriate manufacturing methods. Profiting from the economic advantages and high workpiece quality of mechanical manufacturing methods like forming and blanking, the downsizing of tools is one major challenge in the application of these techniques. This study presents the use of monocrystalline silicon as tool material for blanking. The main reason for the application of this material is the possibility for the miniaturisation of silicon structures by etching down to 100 um and below, which is well-established in the microsystems technology. But to benefit from this knowledge the tool design has to be adapted due to the brittle material properties of silicon. In experimental blanking tests on copper foils with a thickness of 20 um tool wear in form of outbreaks occurs at the cutting edge. The analysis of this blanking process with a wear-modified cutting edge by finite element method shows a shift of critical tensile stresses in the punch in a direction opposite to the wear-free cutting edge. This is in accordance to the experimental results, as in this area new outbreaks begin. These results are transferred to a defined cutting edge modification for a material-adapted tool design. A chamfer and a radius at the cutting edge result in significantly lower tensile stresses in the silicon punch.