Studies on Draw and Thin Redraw Forming : 2nd Report, Effects of Forming Temperature and Speed on Stretch Draw Forming of a Laminated Sheet

Abstract

The stretch draw method is applied to reduce the side wall thickness of a cup by a very sharp die radius under high backward tension. The temperature of stretch draw forming under dry conditions is high, compared with conventional redrawing. The purpose of this study is to clarify the friction characteristics of the laminated sheet, and the effects of tool temperature and punch speed on stretch draw forming. The results indicated that the kinetic friction coefficients (μ_k) on the laminated sheet change with glass transition temperature (T_g) having polyethylene terephthalate/ isophthalate copolymer (PET/I) film. In the case of higher tool temperatures, the thickness reduction rate is not affected by blank holding force (BHF) in the case of backward tension and punch speed is unrelated to thickness reduction. The surface temperature on the cup wall after the stretch draw forming is increased by approximately 1.5 times that of conventional redrawing.