Computer aided tolerancing (CAT) in the automobile industry is implemented by CAD tools. These tools analyze the manufacturability of complex assemblies with rigid single parts in an early stage to reduce the product development time and the cost for hardware prototypes. This paper proposes an approach to implement tolerance simulation for a compliant assembly, which includes manufacturing processes such as clinching, bolting and hemming by applying tolerance simulation tool. The fender- BIW system is simulated as a compliant–rigid system and the simulation model is applied to two production scenarios. The simulation results are compared with real measurement data, which demonstrates the efficacy of using simulation in early production as opposed to prototyping or other methods of design by showing the strong correlation between simulation results and as-built products.

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Tolerance simulation has already been applied throughout the product realization loop in automotive industry to improve the product quality while reducing the product cost. However, the capability of tolerance simulation is limited by the prediction accuracy. Although tolerance simulation methods for non-rigid part are available which involve the elastic deformation during the manufacturing process, there are still difficulties while addressing large deformations and the Body In White (BIW) joining processes, which have non-linear effects. Thus, the Finite Element Method (FEM) based joining simulation raises its importance as it simulates the physical properties of parts in system and helps to digitize the manufacturing process. A proper combination of the manufacturing process simulation with the tolerance analysis contributes to the product and process optimization. In this paper, the current statistical tolerance simulation method is improved by integrating manufacturing joining simulations. The application of the joining-simulation based tolerance analysis is illustrated with an example of a sheet metal assembly in different product development phases. As a result, The critical tolerances are identified in the digital concept phase. The initial specified part tolerances are optimized regarding the assembly deviation requirements on the product characteristics and a given scrap rate. It contributes to reduce the production cost in the prototype phase, where the stamping machines are designed. Besides, the influence of tolerance change on the assembly dimensional quality in the late production phase is evaluated.