Punch design for floating based micro-tube hydroforming die assembly

Conventional punches used in tube hydroforming (THF) are hollow to facilitate supply of pressurized fluid to the die cavity. The fabrication of hollow micro-punches for micro-THF which can sustain punch loads presents a challenge. This study proposes different types of micro punch designs that can be used in conjunction with floating based micro-tube hydroforming (THF) die set-up. Finite element analysis was carried out to determine the feasibility of the proposed punch design variants followed by Micro-THF experiments. The experiments were carried out to hydroform Y, T, and bulge shaped parts from SS 304 1 mm and 2 mm tubular blanks. The study has demonstrated that notched punches can effectively be used in micro-THF. The major benefit of using notched punches is that, longer micro-punches with the desired strength can be fabricated with ease using electrical discharge machining (EDM).