A real-time thermal inaccuracy compensation method on a machining centre

The errors which affect the processing precision of a machining tool are due to the built in volumetric errors in the machine structure, and also the thermal displacement of the machine tool during cutting. In this paper, a new technique is developed to compensate for these errors in machine tools. The work demonstrates that the thermal effect is quite different in air-cutting conditions and real-cutting conditions. An IC type thermometer is designed to detect the temperature variation at specific components of the machine tool. These thermal displacements are measured on-line with a touch trigger probe. A mathematical model is then built, based on the sensed temperature variation and the thermal displacements by multivariable regression analysis. Finally, these errors are reduced on the machine by sending a feedback signal to the CNC controller to improve the processing precision of the machine tool. In this research, the errors are successfully reduced to within 4 µm for general cutting.