Method of surface defects control by tool surface compensation for exterior auto-panels

Surface defects are small concave imperfections that can develop during forming on exterior auto-panel like doors. They occur during springback steps, and the depths are usually from dozens of micron to hundreds of micron. Surface defects can alter significantly the final quality of the automobile and it is very important to predict and control them as early as possible in the design of the forming tools. In order to prove the accuracy of the simulation, a sample panel with a door handle feature is stamped and measured in experiment to be compared with the FEM result. A method of surface defects control by tool surface is advanced. The sample panel with a door handle feature and the sample panel of cylindrical shallow shell are simulated. The quantitative evaluation result of the sample panels' surfaces decrease above 90% after tool surface compensation. And the validity of the method is approved. Tool surface compensation is a method to control the surface defect by changing the elements nodes of tools. This method bases on numerical simulation. After compensating for several times, the reasonable tool surface mesh is gained. It can control the surface defect result in the bending moment by controlling the stress through thickness direction. It provides the solution to control the surface defects in the design of the forming tools. © 2013 Journal of Mechanical Engineering.