Investigation on Coining of Micro-Features Using Pure Copper

Recently, applied research activities on the miniaturization of conventional forming processes have received attention in search for mass production methods for micro-scale metallic parts. This study investigated the coining of micro-features by numerical analyses and experiments. Prior to conducting the experiments, finite element simulation was used to understand the effects of channel aspect ratio, workpiece thickness, channel number, channel geometry, and friction on the coining process. Experiments using pure copper specimens were performed to confirm the findings from the simulation and to study the effects of preform shape and grain size. It was found that the channel depth, workpiece thickness, and channel geometry had a significant effect on the final load, while the channel number did not influence the final load. It was also concluded that certain preform shapes induce favorable flow of the material and result in enhanced formation of the micro-protrusions. For the conditions used in the experiments, however, effects from the grain size were not observed.