| Summary: | 碩士 === 國立高雄應用科技大學 === 模具工程系 === 97 === In this study, the multi-step cold forging processes were used to form the particular shape of flat head tetragon neck bolt. The standard classification of the bolt is M12×1.25×37.5 which used in chassis of car, and SCM435 was used as the material. The diameter of the wire rod is 11.65mm, and its hardness is between 85 to 88 in HRB. The original forming process of the factory is easy to the material fill under in four corners of the neck and the using life of the die is not good. This study used PRO-E and DEFORM-3D (FEM package) to design a better forming process than the original forming process and to analyze the characteristics of the metal forming. Firstly, draw every possible forming processes. Next, use PRO-E to get the files of the punch and die for each step, and then transform the above-mentioned files into STL to be used in DEFORM-3D as geometries and to define the conditions of simulation in the pre-process of DEFORM. Since the product is symmetrical, therefore the billet will be divided into 1/8. It not only decrease the analyzing time but also increases the precision of the simulation. In order to increase using life of the die and raise quality of the product, we find three forming processes. From the three forming processes, we combine them and design an optimal forming multi-step approach. By the results of the analysis, the total forging load and maximum effective stress of the die for optimal forming process is about33.25 ton and 970 MPa lower than the original forming process. It reduced about 16.2% and 17.73% than the original forming process. The optimal forming process could diminish the forming load, die stress and raise the life of die.
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