Time-Varying Error Prediction and Compensation for Movement Axis of CNC Machine Tool Based on Digital Twin

Currently, it is a challenging issue to predict the thermal-induced time-varying error for the movement axis of the computer numerical control (CNC) machine tool. Subsequently, it is a challenge to predict the machining accuracy for a certain workpiece when the machine tool and numerical control program are determined. In order to resolve this shortcoming, the time-varying error prediction and compensation for the movement axis of the CNC machine tool was studied in this article, and the advantage of digital twin in predicting the changing trend for the physical entity was applied. The framework of time-varying error prediction and compensation for the CNC machine tool's movement axis was proposed based on the digital twin concept, which includes the physical entity layer, data transmission layer, function execution layer, and application service layer. The digital twin of the movement axis, containing a time-varying error model based on heat transfer theory and visual model, was created and packaged as a ready-to-use software for predicting and compensating time-varying error. The prediction experiment of the hole-pitch time-varying error for a workpiece was carried out. It was found that the difference between prediction error and actual error is only -0.2-2.6 mu m. The fluctuation range of hole-pitch error is reduced by 69.19% with the time-varying error compensation in real-time. The experimental results show that the method of time-varying error prediction and compensation based on a digital twin is an effective and feasible scheme.