Dynamic characterization of milling plant columns

Building structures the most rigid as possible is a common practice in order to guarantee extremely precise tool spindle positioning. However, very rigid structures are usually very lightly damped and this could lead to some dynamic problems in case of resonance conditions. In the case of milling machines, due to the variety of milling programs and of cutting tool types, the machine tool is often forced by broad frequency spectrum excitation, quite impossible to be predicted at a design stage. Thus a near-resonance working condition could easily appear. In recent years, to increase damping whilst maintaining very rigid structures, metal foam sandwiches have been used. However, it is quite rare to find comprehensive experimental studies demonstrating the effectiveness of this solution on a complete structure, such as a column of a milling machine. In this paper, two columns of a milling machine built using different technologies, i.e. classic metalworking and metal foam sandwiches, are compared. On this purpose experimental modal analysis was applied.