Study on the forming parameters of the metal bellows

The manufacturing process of the metal bellows consists of the four main forming processes: deep drawing, ironing, tube-bulging and folding. The tube-bulging and folding processes are critically important because the quality of the metal bellows is greatly influenced by the forming conditions of these processes. Also, the final convolution shape of the bellows is determined just after the springback stage. There are many forming factors pertinent to the overall process of the metal bellows. The representatives are the wall thickness of the pre-form tube, the pressure applied during the tube-bulging and the die stroke for the folding stage. In this paper, a finite element analysis technique is applied to the tube-bulging and folding processes as well as the springback stage. The explicit time integration method is used for analyzing the tube-bulging and folding processes. Meanwhile, the implicit time integration method is used for the springback stage. Combination of these two different time integration methods is widely accepted for simulating the forming and springback stages consecutively. In addition to the FE simulation, effects of the representative forming factors mentioned above are examined by using the Taguchi method. From the factor study, the most important factor influencing the final shape of convolution of the metal bellows is found out. The results of the present study could be used as a basis of designing a new type of the metal bellows.