Abstract: According to ISO and ASME standard, a thermal errors testing system for planer type numerical control (NC) machine tool is built up. The distribution of spindle box thermal field and its influence on spindle thermal errors are analyzed through constant and vary rotation speed testing. A thermal error elements model is built, and the influence of main spindle thermal errors on machining accuracy is analyzed. It is found that there is flat corresponding relation between spindle thermal errors and temperature, and the influence of spindle thermal expansion in axial direction is far greater than deformation in radial direction. But compare to spindle deformation, the variation of temperature take on the characteristics of thermal delay and thermal inertia. The maximum influence on radial errors of spindle is thermal drift error in the same radial direction and thermal tilt in its vertical radial direction. And the maximum influence on axial errors of spindle is thermal drift error in the axial direction and thermal tilt in the moving direction of worktable. According to the characteristics of thermal errors and its distribution tendency, three types of measures are proposed to reduce thermal errors, including structure optimization, thermal balancing and errors compensation modeling. Their advantages are analyzed.

Key words: Errors compensation modeling, Spindle thermal errors, Thermal balancing, Thermal field