模具专业英语 作者 王浩钢 14456第13章.pptVIP

Lesson 13  Stamping and Punching DiesCompound Die Design 　　A compound die performs only cutting operations (usually blanking and piercing) which are completed during a single press stroke. 　　A characteristic of compound dies is the inverted position of the blanking die and blanking punch which also functions as the piercing die. 　　As shown in Figure 13-1, the die is fastened to the upper shoe and the blanking punch having a tapered hole in it and in the lower shoe for slug disposal is mounted on the lower shoe. 　　The guide pins, or posts, are mounted in the lower shoe. The upper shoe contains bushing which slide on the guide pins. 　　The assembly of the lower and upper shoes with guide pins and bushing is a die set. Die sets in many sizes and designs are commercially available. 　　On the upstroke of the press slide, the knock out rod of the press strikes the ejector plate, forcing the ejector tie rod and shedder downward, thus pushing the finished work piece out of the blanking die①. 　　Four special shoulder screws (stripper bolts), commercially available, guide the stripper in its travel and retain it against the preload of its springs. 　　The blanking die as well as the punch pad is screwed and doweled to the upper shoe. Bending dies 　　Bending is the uniform straining of material, usually flat sheet or strip metal, around a straight axis which lies in the neutral plane and normal to the lengthwise direction of the sheet or strip. 　　Metal flow takes place within the plastic range of the metal, so that the bend retains a permanent set after removal of the applied stress②. 　　The inner surface of a bend is in compression; the outer surface is in tension. A pure bending action does not reproduce the exact shape of the punch and die in the metal; such a reproduction is one of forming. 　　The neutral axis is the plane area in bend metal where all strain is zero. Bending methods 　　Metal sheet or strip, supported by a V block, is forced by a wedge-sha