Research on Mechanism Model of Fixture Location Errors Analysis

A new methodology using mechanism to model fixture location error (FLE) is proposed. Typically, there are four elements related to accumulation and propagation of FLE in workpiece-fixture system (WFS), which are machining feature, process datum, location datum and locators, and the relative position variations among them correspond to various FLEs. In this research, the four elements are treated as link mechanism components, the concatenation between location datum and locators is represented by contact pair, which is transformed to kinematic pair in equivalent mechanism, and geometry & dimension tolerances are simulated by link mechanisms. The rules mapping from FLE elements to their equivalent mechanisms are established, and by which the WFS is transformed into an equivalent mechanism model system. The method is studied that the process parameters of WFS are calculated by the structure parameters and kinematic parameters of equivalent mechanism. Thus, the solution of location error can be realized by means of the position analysis methods of mechanism.