Studies on Draw and Thin Redraw Forming : Investigation of Composite Working Conditions for Stretch Draw Ironing Combination Forming using a Laminated Sheet

One of the forming methods to reduce weight and save material in laminated products is stretch draw ironing combination forming. This combination dry forming process is carried out without using a coolant/lubricant because of the good sliding property of the polyester film. The main purpose of the stretch draw ironing method is to reduce the cup wall thickness by more than 30% without damaging the laminated film. From the experimental results, the decrease of the forming load related to wall breakdown can to obtained by setting the initial draw ratio to be larger and the 1st redraw ratio to be smaller. Higher side wall reduction and thickness can be obtained by setting the redraw die radius (Rd/to) or clearance of punch and ironing portion smaller. In particular, the influence of the ironing clearance (Cl) is marked. The ironing reduction and punch temperature are affected by the stripping-out load in removing the cup from the punch. Further reduction becomes possible by the combining the stretch draw process, which produces less damage, and the ironing, which gives greater stability.