钣金件冲模设计---外文翻译.docVIP

Sheet Metal Die Design A brief introduction on the sheet metal blanking and piercing dies is presented in Chapter 21. In practice component is produced essentially by combinations of blanking, piercing, bending or drawing operations in a certain order. The dies discussed previously are involved in carrying out only a single operation. But the most practice dies have to do more than one operation for making a finished component. In this chapter, the details of the design of such dies are discussed. 22.1 TYPE OF DIES The sheet metal dies can be broadly categorized into three types: progressive dies, compound dies, and combination dies. Progressive dies The progressive dies perform two or more operations simultaneously in a single stroke of a punch press. so that a complete component is obtained for each stroke. The place where each of the operations are carried out are called stations. The stock strip moves from station to station undergoing the particular operation. When the strip finally leaves the last station, a finished component is ready. An example is presented in Fig.22.1. At the start of the operation, the sheet is fed into the first station. After undergoing the operations at this station the ram of the press moves to the top and the stock is advanced from the first station to the second station, while a fresh portion of the stock comes under the first station. The distance moved by the strip from station one two so that it is properly registered under the stations is called advance distance. This advance distance should be the same between any two stations in sequence. Another variable called the feed distance is the amount of stock fed under the punch when ram comes for the next stroke. The feed distance may or may not be the same as the advance distance. The reason for the variance between the feed distance and advance distance, that is sometimes observed is because, often the sheet is overfed against a stop. The strip is, therefore positioned correctly