To analytically estimate the 3D position deviation of a holes pattern due to fixturing

This work considers how deviation on fixturing elements propagate on location tolerance of a holes' pattern. The 3-2- 1 locating principle has been adopted. The position of each locator is represented by a Gaussian probability density function and, consequently, the probability the holes pattern falls inside the location tolerance, centred around each hole nominal position, is estimated as the product of the probabilities due to each hole. The optimal positioning of the locators is designed by minimising the deviation in holes pattern positioning during drilling due to locators inaccuracy. 3D parts have been considered as application examples.