Modelling thermomechanical behaviour of multi-axis machine tools

A new measurement technique is proposed for the assessment of thermally induced errors of machine tools. The basic idea is to measure changes of length by a telescopic double ball bar (TDBB) at multiple locations in the machine's workspace while the machine tool is thermally excited with various duty cycles. In addition to the measurement method, a thermal machine error model is proposed for software error compensation purposes to enhance the machine's positioning accuracy significantly. This model describes the relative positioning error of the tool with respect to the workpiece table as a function of axis position and temperature. Numerous validation measurements reveal that about 60\% of the thermally induced errors can be described by the thermal machine error model propose