Geometric and thermal error compensation for CNC milling machines based on Newton interpolation method

Abstract

The fast and accurate modeling for machine errors is an important step for the implementation of error compensation. In this article, a new approach for real-time compensation of geometric and thermal errors is presented, including an accurate error model and a real-time error compensation system. An experiment is carried out on a three-axis milling center to obtain machine positioning errors under different temperatures. A serial of error data collected under normal temperature is regarded as the basic error and modeled with the machine position coordinates based on Newton interpolation method which is also used for modeling the other error curves under different working temperatures in order to get their coefficients of fitting formulas. According to the relationship among these formulas, all the coefficients and the corresponding temperature variations are modeled using the Newton interpolation method again. The final compensation model can be obtained by substituting the coefficients of basic error formula. In addition, an external real-time error compensation system is developed based on the function of external machine zero point shift in Fanuc CNC systems. Experimental results show that the proposed geometric and thermal error compensation system can be utilized as an effective manner to improve the accuracy of CNC milling machines.