Fabrication of Miniature Shell Structures of Stainless Steel Foil and Their Forming Limit in Single Point Incremental Microforming

Abstract

Single Point Incremental Microforming (SPIMF) using neither dies nor a backing plate is applied to the fabrication of miniature shell structures of stainless steel foil in meso-scale. A piece of 8 µm-thick blank, which is held in a blank holder on a desktop forming machine, is incrementally formed with a thin, round-tip tool. Three kinds of polygonal pyramids are formed, and their forming limits are compared to those when 12 µm-thick aluminum foil is used. It is found that the forming limit of stainless steel foil in forming pyramids depends only on the tensile strain of a triangular lateral face, whereas that of aluminum foil depends on the sum of two principal tensile strains on the surface of a rounded lateral edge. It is also found that the forming limit of stainless steel foil can be drastically increased by SPIMF.