Simulation of Warm Forming Assisted Hemming to Study the Effect of Process Parameters on Product Quality

Current trends in the auto industry requiring tighter dimensional specifications combined with the use of lightweight materials, such as aluminum, are a challenge for the traditional manufacturing processes. The hemming process, a sheet metal bending operation used in the manufacturing of car doors and hoods, poses problems meeting tighter dimensional tolerances. Hemming is the final operation that is used to fasten the outer panel with the inner panel by folding the outer panel over the inner panel. Roll in/out is one of the main quality concerns with hemming, and keeping it under tolerance is a high priority issue for the auto manufacturers. Current hemming process technology, given the mechanical properties of current materials, has reached its saturation limit to deliver consistent dimensional quality to satisfy customers and at the same time meet government standards. Combining warm forming techniques with the traditional hemming process represents a new approach with the potential to overcome the current hemming limitation and to provide a satisfactory solution to all the requirements. The main objective of this research is to understand the effect of localized heating on the final quality in the hemming process by quantifying the influence of key geometrical and process parameters. To achieve this goal, a hemming finite element model, taking into consideration the mechanical properties as function of temperature is developed, and statistical methods to quantify the effect of key variables are employed. As an outcome to this study, the effectiveness of using warm forming techniques to improve hemming quality is assessed for A5182O aluminum, one of the most common used materials for this application.