Analysis and modeling of the thermal errors of carriage system of a precision machine tool driven by linear motor

The drive system with linear motor of precision machine tools can generate a lot of heat and part of it is conducted to machine tools structures. Therefore, it can lead to the thermal deformation of the structures and hence seriously influences the processing accuracy. In this paper, the finite element model (FEM) considering convection of the planes, the pipelines of the cooler system and thermal resistance is adopted to investigate the thermal distribution and thermal deformation of the carriage system of precision machine tools driven by linear motor. In addition, position-independent thermal errors models of the carriage system are proposed for the main heat source, the primary part of the linear motor, of the carriage system travels with the worktable; the feature genetic algorithm is used to procure the thermal key points of the carriage due to the great number of candidate points. At last, the experiment is conducted on the Y-axis carriage system of precision three-axis machine tool, which demonstrates the two geometric errors δx and εz caused by the thermal deformation are significantly tiny. The mathematical models of three thermal errors are obtained through the temperatures of the key thermal points because the interferometer cannot measure the roll error εy. Also, the comparison between the measurements and the thermal errors models indicates that the position-independent thermal models are capable of satisfactorily predicting the magnitude of the other three geometric errors of the carriage system caused by the thermal deformation and also being used in further study of compensation system.