Tolerance allocation using Monte Carlo simulation

Tolerance allocation is an important issue in product manufacturing, ensuring on the one hand the interchangeability of parts in an assembly and on the other hand, it has a major impact on the costs of manufacturing products and quality. This paper aim is to assign in a 2D dimensional chain with, dimensional and geometric tolerances, dimensional and angular (geometrical tolerances) values to dimensions in a variation interval in order to obtain a design required variation in dimension and angle for the closing element of that chain, using the Monte Carlo (MC) simulation. MC simulation randomly assigns values of the dimensions of the dimensional chain (DC) - for their module and angle - to their tolerance field, and then calculates the range for module and angle (R) caused at closing dimension in a sufficiently large number of cases. The ratio of the desired tolerance (Tdo) to the dimension chain closing element and the range (R) resulting from the simulation, respectively Tdo/R are calculated and compared with a value that must be greater or at least equal to an imposed value of an index dependent of the Cp - capability desired at the closing dimension. At the desired value that meets design requirements, the tolerance allocation process is completed.