Deep Drawability of Polymer and Composite Sheets using a Flexible Punches with Hydraulic Counter Pressure

采用柔性凸模研究了液压对聚丙烯（PP）和玻璃纤维增强聚丙烯（GFPP）片材圆筒形件拉伸性能的影响。实验测得的冲压力，侧壁的厚度和高度在拉深帽，并与传统的使用刚性冲头拉深进行了比较。使用柔性冲头，发现拉制杯所需的力低于使用刚性冲头拉制时所需的力。虽然这被认为是有利的，但在这种具有用于聚合物和复合片材的模具和冲头的常规拉伸工艺中，发生了杯壁变薄的扩大。这种壁变薄的现象导致液体从凸缘流出，导致反压泄漏。因此，使用模环和聚氨酯垫自由成形聚合物片材，并使用薄聚氨酯环和金属冲头用Maslennikov技术对聚丙烯片材进行深杯拉伸。该技术的拉伸方法对聚合物的拉深加工起到了减少杯壁减薄的良好作用。与使用传统工具进行聚合物成型相比，使用柔性工具可以获得几个优点。

Influence of hydrauric pressure on the cylindrical cup drawability of polypropylene (PP) and glass fiber reinforced polypropylene (GFPP) sheets is investigated using a flexible punch. Experimentally measured punch forces, the thickness of side wall and the height in the drawn caps are presented and compared with conventional drawing using a stiff punch. Using a flexible punch, the force needed to drawn a cup found to be lower than that needed when drawing with the stiff punch. Though it was seen to advantage, in this conventional drawing process with a die and a punch for the polymer and the composite sheets, an enlargement in thinning of the cup wall occurred. This phenomenon in thinning of the wall produces an outflow of liquid from the flange which causes the counter pressure to leak.Consequently free forming of a sheet polymer using a die ring and a urethane pad, and drawing deep cups with Maslennikov's technique using a thin urethane ring and a metal punch were carried out for polypropylene sheet. Drawing method of this technique can perfom the good function of the reduction in thinning of the cup wall for the deep drawing processing of polymers. There are several advantages to be gained with the use of flexible tools over the use of conventional tools for polymer forming.