A novel design to minimize errors due to trimming in sheet metal forming software

Abstract

The forming operations start with forming of metal and then trimming the unnecessary part and finally spring back calculations. After completing forming operation, by means of a curve defining trimming boundaries, unnecessary parts are trimmed, similar to the real operations. However in numerical environment after trimming new mesh generation around the trimming boundary is unavoidable. The strains calculated for forming operation are mapped on to the new mesh generated after trimming. The new nodes created can not find any corresponding strains. Although the number of new node, are not too much with respect to the total number of nodes on a sheet formed, they are the main causes of errors in spring back operations. In this study to overcome this problem a new approach is recommended. In this approach., before trimming operation, the strains found on the sheet after forming are used to find SR (surface-regression) for the studied sheet. Since SR can define the strains for any x, y and z coordinate, the nodes after trimming operations can find approximated strain values. This method was applied on real parts and it was found that the errors are almost disappeared.