Forming of micro gears by compressing a pure copper sheet through its thickness

Abstract

Currently, micro gears are mostly fabricated by LIGA technology and micromachining. These processes have some limitations. Forming processes not only satisfy mass production and appropriate productivity rate but also present superior mechanical properties. A major problem preventing the bulk micro metal forming is the preparation of micro billets and their precise transfer between the forming stages. The purpose of this study is developing a method to form a micro gear without the need to a separate micro billet preparation. In this paper, pure copper sheets were compressed into the predetermined micro gear profiles though their thicknesses, so that there is no need for preparation of micro billets and also its troublesome transforming. The tests were performed at room temperature, in two cases of single extrusion process and extrusion-forging process. Micro gears with 6 teeth and 250μm in module were formed completely with good repeatability in both the cases. A major advantage of the proposed study compared with the blanking process is that, in blanking, the process is merely cutting the edges, while here the material fills the die by deformation. Thus, better mechanical properties will be achieved. Measuring the micro-hardness of the formed parts in comparison with raw material, verified this point. In general, the micro-hardnesses of combined extrusion-forging parts were higher than those of single extrusion ones in the same positions on the micro gears surface.