Abstract: In order to improve the machine accuracy, a synthesis modelling method of geometric and thermal error is presented. Machine error distribution law is obtained through the analysis of machine error data at varying temperatures. Based on the different characteristics of geometric error and thermal error, error separation is carried out. Synthesis mathematical model for geometric and thermal error is proposed by using polynomial fitting and linear fitting. Online real-time error compensation is implemented by applying the computer numerical control(CNC) external machine coordinate system shift function and a novel developed synthesis error real-time compensation system. This error compensation method concerns the geometric error and its variations at different temperatures, thus a comprehensive analysis is made on the error and its regularity in the overall temperature rise to the heat steady-state. The inspection certificates that the maximum positioning error in normal temperature is reduced from 44.1 μm to 3.6 μm by applying the error compensation method and real-time compensation system, which is compensated 91.8% compared with no compensation. After the temperature rise, the maximum positioning error in normal temperature is reduced from 26.0 μm to 5.1 μm, which is compensated 80.4% compared with no compensation. The machine accuracy is effectively improved.

Key words: Geometric error, Real-time error compensation, Synthesis error compensation system, Thermal error