Simple and Effective Method to Compensate Thermal Deformation of a Machine Tool by Deriving its Approximate Equation (Application under the Continuous Operating Condition)

This study presents a simple method to compensate the thermal deformation by measuring temperatures at only a few points of a CNC lathe. We have confirmed the thermal deformation of the main spindle of the lathe strongly depends on changes of temperatures at the headstock and ambient. Therefore, the present study measures the thermal deformation with respect to the temperature changes of these points and considers these relations. From the results, the approximate equation of the thermal deformation dependents on the temperature of the headstock is derived as a function of the temperatures of a few points and the rotational speed of the main spindle. Furthermore, the approximate equation of the thermal deformation of the ball screw is likewise derived as a function of the ball nut and ambient temperatures. By using the estimation value of the thermal deformation obtained from both approximation equations, the work error is compensated. The present study demonstrates the cutting processing in view of the estimated values of the thermal deformation obtained from the derived equations and confirm the work error will be remarkably reduced.