Estimation of Thermal Deformation of Machine Tool by Utilizing Available Information in CNC Unit

Abstract

A new method is proposed in the present research to estimate thermal deformation of machine tools. The present method utilizes available information in CNC units instead of external sensors such as thermocouples and strain gages. An estimation model utilizing transfer functions and a method to identify them are developed, and it is applied to estimation of the thermal deformation of a machining center caused by rotation of its main spindle and feed motion of the tables. The transfer function matrix between the thermal displacements and the heat generating factors, i. e. rotational speed, primary motor current and secondary motor current, is identified by the impulse response method. The thermal displacements are estimated by employing the identified transfer function matrix while the main spindle and the feed tables are driven at various speeds. It is confirmed by the experiment that the estimated displacements agree roughly with the measured ones.