A New Monte Carlo Simulation Method for Tolerance Analysis of Kinematically Constrained Assemblies

A generalized Monte Carlo simulation method is presented for tolerance analysis of mechanical assemblies with small kinematic adjustments. This is a new tool for assembly tolerance analysis based on vector-loop-based assembly models with kinematic assembly constraints. Methods have been developed for simulating both closed loop and open loop assembly constraints as well as over-determined assembly systems. Both dimensional and geometric feature variations of the components may be included in the assembly simulation. Compared to the traditional Monte Carlo simulation of mechanical assemblies, the new method does not require explicit functions to describe the assembly parameters. Explicite functions are often quite difficult or impossible for designers to obtain for 2-D and 3-D assemblies. An iterative nonlinear solution is required for each simulated assembly to assure that closed loop assembly constraints are satisfied. A general four parameter statistical distribution is fit to the resulting assembly data for estimating percent rejects.