装载机轮缘(图1)是一个热成型件,原加工工艺过程是将钢板卷成圆筒,焊牢接头,加热后在两套成型模上分两次成型。第一次是在图2a所示的模具上完成预成型。使用该模具在凸模下压回程时,由于工件内表面紧贴着凸模较凉的表面,冷却较快而急剧收缩,工件紧箍着凸模很难取下。若事先将凸模预热到一定温 Loader rim (Figure 1) is a thermoformed parts, the original processing process is to roll into a cylinder steel, welded joints, heated in two forming molds on two molding. The first time the preforming is done on the mold shown in Figure 2a. When using the mold to press back the punch under the punch, the inner surface of the workpiece is close to the cooler surface of the punch, so the rapid cooling and rapid shrinkage make it difficult for the workpiece to be clamped with the punch. If the punch preheated to a certain temperature in advance