Portability of the thermo-mechanical compensation model of the milling center

Abstract

Thermo-mechanical errors of machine tools (MT) are important element in inaccuracies of machined workpieces. In the past few decades, thermal errors have been successfully reduced by techniques of software compensation. For example, the multiple linear regression analysis, the finite element method, the neural network or the transfer function (TF) are used. Approximation model based on dynamic method of TF is used for compensation thermal errors in this publication. The approach respects basic mechanisms of heat transfer in the MT structures. Every single piece of produced MT is original due to manufacturing inaccuracies of MT compo-nents, assembly process (different preloads in bolts, deviation in the assembly and seating of components, etc.) or working environ-ment of the MT (e.g. air-conditioned or common factory hall, etc.). Usually, MT producers offer the same type of the MT equipped with different components (e.g. spindle units) which leads to further differences in thermo-mechanical behaviour. The aim of the article is to define conditions and examine issues of transfer of existing thermal error compensation model between several machines of the same product line; taking into account manufacturing and assembly inaccuracies and changes in working environment. Selected machines were tested during non-stationary activity of the main heat sources: different spindle units and two linear axis movements.