Effects of cooling systems on the thermal behaviour of machine tools and thermal error models

Abstract

Achieving a high workpiece accuracy is a long-term goal of machine tool (MT) designers. There are many causes of workpiece inaccuracy, with thermal errors being the most dominant. Redesign of MT structure, heat flux control, prediction of MT thermal behaviour or software compensation provide solutions in the thermal issue of MTs. Since the reconstruction is usable in MT prototype stage mostly and accuracy of predictive models depends on precise boundary condition determination and huge computing time, a software compensation (using approximation models) along with adaptive heat flux control are promising widely employed strategies to reduce thermal errors of MTs already used in production lines. A modelling approach using transfer functions (TF) has the potential to deal with the issue. It is a dynamic method with a physical basis and its modelling and calculation speed are suitable for real-time applications. This research summarises the scientific investigation into the modelling and control of machine tool thermal behaviour. First, TF models used in adaptive cooling development are presented. Afterwards, sensitivity of MT software compensation model to changes in main heat source and untested inputs is discussed.