Abstract
Dimensional precision control in auto body assembly process is most important to assure the perfect fitting of outer panel with closures, and to decrease the wind noise and vibrations of the car during driving. Because of the deformation of sheet metal on fixture, dimensional variation analysis is difficult because the traditional dimension analysis methods for rigid parts were not suitable. Based on the widely used N-2-1 locating mode, this paper proposed a variation sensitivity model by combining the Finite Element Method and variation sensitivity analysis. Two sets: (1) fixture features sets, and (2) key dimension sets of parts or subassemblies are defined and included in the model as input and output. Measuring noise of measurement system is also considered. Potential value of this model is to optimize the locating and clamping mode of welding fixture in order to acquire the minimum dimensional variation. Based on this model, a Statistical Simulation Analysis method was provided to analysis the influence of each fixture elements' variation on the measured variation of key dimension points.