Micro-scaled progressive forming of bulk micropart via directly using sheet metals

Abstract

In our prior study, a progressive forming system to fabricate meso-scaled bulk cylindrical and flanged parts by using sheet metals has been developed. In this forming system, the cylindrical part is formed via blanking, while the flanged part is formed via the progressive punching, extrusion and blanking. In forming of the flanged part, the preform is attached to the metal strip and positioned based on the geometry of preform. The formed part is finally trimmed out by shearing in the last operation. In such a way, the transporting, positioning and ejecting of preform/part are facilitated. In this paper, the research is aimed at further studying the feasibility of forming microscaled parts by using the previously developed forming system and examining its characteristics based on the material flow behavior, microstructure evolution, the quality and property of the final formed parts. It is revealed that the length of blanked cylinder decreases with the increase of grain size. When the grain size is large compared to the workpiece thickness, an inclined fracture surface is formed on the blanked cylinder and the rollover surface on the flanged part becomes rough. A rough fracture surface with microvoids is formed after shearing operation. The number of microvoids on the fracture surface decreases with the increase of grain size. The developed process is proved to be promising and efficient for mass production of bulk microparts directly using sheet metal.