Comparison of updating strategies to improve finite element models of multi-axis machine tools

In this paper, two alternative strategies to update finite element models of multi-axis machine tools are analyzed. The aim is to obtain improved numerical models that simulate adequately the dynamic behavior of the machine tool over a wide range of operating conditions. First, one- and multiple-configuration strategies are defined according to the number of spatial configurations of the selected machine tool. Then, using experimental modal data and iterative updating techniques, both strategies are tested on a three-axis machining center. Results show that, whatever the strategy selected, relative differences between numerical and experimental natural frequencies are decreased considerably after model updating. Nevertheless, one-configuration strategy provides much better results in the configuration selected as reference than in the other, while multiple-configuration strategy leads to attractive results for any spatial configuration. Thus, machine tool designers have at their disposal two possible strategies, so that depending on the characteristics of the machine tool and machining processes, may choose the most convenient. In addition, it is shown that multiple-configuration strategy enables to generate efficient finite element models for multi-axis machine tools using experimental data from a few specifically selected spatial configurations. As a result, the improved models will facilitate to establish reliable valuations about the necessity of performing design modifications, and will be the basis to accurately obtain the stability ranges of the machine and consequently diminish chatter vibrations.