| The die design and manufacturing is a bottleneck of large automobile body panel which restricts the development of our country’s automobile self-owned brand. In traditional die design, not taking into account of the unequal clearance between die and punch, the contacting ratio should be higher theoretically. However, when the die is on the lower limit, the gap between die and punch is inconsistent with the thickness distribution of the stamped part, which leads to low contacting ratio, especially the “hollow” phenomenon frequnetly observed in the middle of large automobile body panel. The gap is small at the margin, so only this part of die contact well. The closer to the center, the bigger the gap is. It ’s mainly caused by the elastic deformation of stamping die structure and press. In order to eliminate this influence and improve contacting ratio, we need physical die try-out to enhance stamping part quality which leads to long cycle of die structure design and large labor cost.With regard to the problem mentione d above, this article makes a in-depth research. A new methodology for die structure and compensation on the die surfaces is presented considering three key influencing factors, the elastic deformation of die, the blank thinning and the deformation of press. What’s more, the grid mapping algorithm based on binary search is developed to realize the accurate mapping between different meshes for the methodFirst of all, this paper summarizes the current situation and development trend of grid mapping algorithm. A new grid mapping algorithm is developed based on binary search, which builds the force transfer between stamping parts and die surface. The algorithm mainly includes two advantages. On the one hand, it improves the search speed. The algorithm converts 3d into one-dimensional and is conbined with binary search which greatly improves the search efficiency. On the other hand, it improves mapping accuracy. In order to avoid the influence of the search radius, it takes a different search direction which use stamping grid node to search the die grid node, avoiding the possibility of giving the stamping nodal force to different die grid node.Secondly, the grid mapping algorithm this paper presented is applied to the car front door outer panel die structure analysis. Then the compensation amount caused by the die elastic deformation is calculated, which is used to guide the modification of the die surface. The grid mapping algorithm map the contact forces obtained from stamping simulation to the die structure analysis model as force boundary conditions. This method is called the die structure coupling analysis method, which is compared with Ls-dyna die structure analysis.Finally, in view of the low contacting ratio and poor appearance quality, a new methodology for compensation on the die surfaces is presented. This compensation method not only take into account of the impact of the elastic deformation of tooling and press, but also consider the impact of the blank thinning and other factors. The die face will be modified based on the amount to compensate this deformation and meets the design requirements in early design stage. A case study is conducted which adopts this compensation method in the die surface design of a car front door outer panel. It shows that the methodology can obviously improve the contacting ratio at the first time, and it discusses the percentage of the three key influencing factors that lead to low contacting ratio.The research results indicate that this d ie surface compensation method can compensate the die and press deformation in the design phase. Application example shows that the new mapping algorithm not only improve the accuracy but also improve the search speed. The methodology can largely solve the problem of low contacting ratio, which is of great value to guide the accurate design of automotive body panel stamping. |
