Fabrication and Investigation of a Micro-Progressive Die Set for Microforming of Sheet Metals

Progressive microforming is an attractive option for manufacturing high aspect-ratio micro-parts out of sheet metal. It is a highly economical alternative to both MEMS processing and micro-machining due to the ability to produce near-net shape parts through parallel forming processes. Current limitations in the field include precise alignment of microforming tools and an understanding of forces encountered when scaling down traditional forming processes. A five stage micro-progressive aluminum die set consisting of four shearing stages and one bending stage was fabricated by micro-machining. The die set was designed to produce right angle micro-brackets from 25 um thick annealed copper foil, with a measured average grain size of 47 um. Die clearances were set at 3 um along shearing edges and 38 um along the bending edge, corresponding to 12% and 152% material thickness, respectively. The produced micro-brackets are intended to be used as electrical connectors and consist of a nominally 280 um by 260 um tab extending vertically from a 780 um by 260 um base. In order to implement and investigate the progressive microforming process, a novel micro-press system was constructed which allows for precision alignment of the die set and workpiece. Using a prepared workpiece, forces at the first stage of the die set were measured and compared to analytical predictions based on models from the literature.