Conceptional setup design oriented locating error analysis for workpiece-fixture system

Inaccuracies of machining fixture's location cause a deviation of workpiece from its nominal geometry position. To achieve an acceptable machining part, this deviation must be controlled within the allowed limits specified by corresponding geometric tolerances. In this paper the relationship between the locating inaccuracies and the machining errors is studied. By geometry analysis, a mathematical model to predict the deviation of workpiece at a feature resulted by a set of known location deviation of locators is formulated. Further, optimum method is employed to achieve allowed locator error bounds according to that the required workpiece geometry tolerance at a feature is not violated. A simplified method is put forward to facilitate the solution of the optimum process. The method can be used to verify the fixture design and error analysis for multiple stations machining process. Finally, a case study has been used to support and validate the proposed model.