Analysis and optimisation of a cold forging die

摘要

Most manufactured products consist of a number of parts that must be fastened together to allow for ease of assembly and disassembly, and frequently threaded fasteners are used for this purpose. The most difficult part of the production of a mechanical fastener, for example, a countersunk head cap screw, used extensively in aerospace, automotive and biomedical applications, is the design of the tooling used to form the fastener. Unfortunately, because of the severity of the cold forming processes used, and the complexity of the material flow during the forming process, tool design is difficult and, as a result, premature tool failure or excessive wear are frequent occurrences. This paper presents the results of an elastoplastic finite element analysis (FEA) using the finite element (FE) package DEFORM to analyse an existing tool design for the formation of an M6 countersunk headed high strength fastener. The FE analysis clearly identified the regions of the tooling susceptible to failure and, on the basis of the FE results, changes were made to geometrical features of the tool design and the interference between the carbide and stress ring so as to reduce the likelihood of premature tool failure. A more comprehensive coverage of this topic can be found in the MSc thesis Advanced Techniques for Forging Sequence Design, University of Dublin, 2004.