Comparison of the dynamic response of two columns of milling machines made of standard carpentry and metal foam sandwiches

In this paper, a comparison between two different machine tool columns is presented. The two columns are realized with a different technology: classic metalworking versus metal foam sandwiches. The aim of the experimental tests is the evaluation of their different mechanical performances and characteristics, with a particular focus on the dynamic response and on the convenience to consider system damping as a key parameter. This kind of comparison is generally believed as difficult, because the foam-filled structures usually show not-linear behavior, which makes not applicable the usual experimental modal procedures. The comparison is carried out in terms of both modal analysis and wide frequency range excitation, as described in the paper. A new method is introduced by the authors to deem which technology is the more suitable, based on overall dynamic response in a wide range of frequency, rather than on modal damping.