Modular tool concept and process design for micro impact extrusion

Micro impact extrusion is an appropriate mass production technology for micro structuring of sheet metal. The technology was applied to form sample geometries consisting of ten precision cavities which are intended to be collets for the form- and force-locked integration of piezo rods for later usage of the sheets as “smart sheet metal”. For reasons of flexibility, a modular tool concept was studied and applied. It allows a flexible arrangement of geometry elements but introduces new aspects which need to be considered. This study investigated the influences of tribological- and process parameters onto the microforming process. Therefore forming experiments were performed with different die coatings (titanium nitride, titanium carbon nitride, amorphous carbon), different lubricants (common oil, forming lubricant and without lubrication), as well as two die materials. In contrast to forming processes with established monolithic die configurations, phenomena like tilted structures and the appearance of unwanted burr were investigated. For creating structures with minimal tolerances, these effects need to be considered. The investigation of the influence of process parameters showed, that the lowest surface roughness was achieved without lubrication. Furthermore low-friction coatings and harder die materials improved the forming results.