机电专业英语 教学课件 作者 杨寿智 刘水平 机电专业英语.Lesson 10.pptVIP

Lesson 10 Die Components Text The components generally incorporated in a blanking or piecing die are shown in Fig.10.1 a .The cutting tool assembly is shown in the conventional closed position. The die set is made up of the punch holder, which fastens directly to the ram of the punch press, and a die shoe, which fastens to the bolster plate of the punch press. Guideposts may be used to better align the punch holder with the die shoe. The die set may be purchased with two guide posts located at the rear of the die set（called back posts）,diagonally, one in the rear and one in the front of the die set, or with four posts, one in each corner. In the conventional position the punch holder is press fitted with bushings. The guide posts and the bushings have a slip fit so that the guide posts may move freely in the bushings. The opposite ends of the guide posts are press fitted into the die shoe. The punch is fastened to the punch holder and aligned with the opening in the die block which is fastened to the die shoe. Since the punch and die block are the cutting tools, they are both hardened. Once the cutting action has taken place, the punch starts to retract. Because of the nature of the material the hole in the scrap strip contracts and the strip clings to the punch, whereas the blank workpiece expands and clings to the die opening. A stripping action is needed to free the scrap strip from the punch. The stripper shown in Fig. 10.1 a is the simplest of such. Its purpose is to align the blank and strip the scrap off the punch on the upstroke. Other types of strippers used are spring pads or plates; some are hydraulically operated. Besides the clinging of the scrap to the punch and the clinging of the blank to the die opening, a third set of forces is operating. The blank also adheres to the face of the punch. If the forces holding the blank to the face of the punch are greater than the forces holding the blank in the die opening, push-off pins are necessary to help t