Development of a combined bulging-piercing technique to reduce forming load for a long semihollow stepped part

This paper aims to develop a new forming technique manufacture long semihollow stepped part. Traditionally, hot backward extrusion is used, but this not suitable because it requires very high load act on the die and punch, especially at contact between punch workpiece. As result, service life of low. Therefore, overcome problem needed. A combined bulging–piercing was proposed developed in research. The main concept bulge part by upsetting workpiece counterpunch generate frictional pressure, which will help restrain material from sliding down into cavity during piercing step. In other words, utilizes force die–workpiece interface reduce punch. Finite element modeling employed investigate determine level bulging can without generating any significantly counterpunch. Only experiments with minimum were selected implemented validate conditions risk damaging machine press product line. results show that almost 40% also control good concentricity wall thickness variation.