A study of thermal deformation in the carriage of a permanent magnet direct drive linear motor stage

Carriage deformation due to temperature gradients within the materials of the carriage affects the accuracy of precision machines. This is largely due to the indeterminist temperature distribution in the carriage's material caused by the non-linearity of heat transfer. The joule heat from the motor coil forms the main heat source. When coupled with the heat loss through convection and radiation, the temperature variation in the motor's carriage also increases. In this study, the Finite Element Analysis was used together with a set of boundary conditions, which was obtained empirically, to analyze the distortion of the motor's carriage. The simulated results were compared with those obtained through experiments. The study shows that it is important to know, rather than to assume, the thermal boundary conditions of the motor's carriage of a precision machine in order to accurately estimate the thermal deformation of the carriage in precision machining.

► Deformation occurs in carriages which are mounted with linear motor.
► The convective coefficient, which is assumed to be 10 W mm−2, is shown to be invalid.
► The perfect contact conductance is shown to be invalid too.
► To have an accurate thermal model, boundary conditions have to be realistic.
► Boundary conditions are the heat source, convective and conductance values.