Error model of a precision two-dimensional fixture

Abstract

This study established an error model based on the normal vector of the machining surface to optimize the structure design of a special fixture for the ultra-precision process of single-crystal germanium two-dimensional drum. Aiming to analyze and reduce the angle error of the drum machining surface, the model includes 10 error items affecting the fixture’s accuracy, such as bearing error and encoder error. It can analyze the repeated positioning error of the fixture and intuitively predict the angle error of the machining surface of the drum. According to existing fixture error data, we used the Monte Carlo method to predict the fixture’s repeated positioning error and related angle errors. We conducted the verification by measuring the repeated positioning accuracy of the fixture and the angle error of the drum processing surfaces, which have machining on the fixture. The results show that the difference between the actual measurement results and the predicted results is 32″. The predicted angle error of the drum processing surfaces is consistent with the actual measurement. According to the sensitivity analysis of each error factor and error component, the error factors influence the fixture error and the angle error of the drum processing surfaces. Finally, we put forward the optimal design scheme of the fixture.