Error Analysis in Multistage Machining Process Using Kinematic Analysis of Workpiece Fixturing

摘要

Fixtures are used to locate and hold workpieces with locators and clamps. As well as having a locating function, fixtures must also ensure that the dimensional quality of the manufactured workpiece can be achieved. Inaccuracies in fixture's location scheme result in a deviation of the workpiece from its nominal specified geometry. A "multistage" machining process refers to a part that is machined through different setups. At multistage machining, the errors of pervious stages are transferred to next stages. In this paper, an analytic model is developed to integrate the errors in each stage and accumulated error of pervious stages. This model has great potential to be applied toward fault diagnosis and process design evaluation for the multistage process. A mathematical model is developed by the kinematic analysis of the fixture using Jacobian matrix and homogeneous transformation matrix (HTM). The effectiveness of the resultant deviation model is verified by example.