Preliminary tests have been executed to investigate the structural damping: an electro-dynamic shaker applied a sinusoidal force at the work piece point in the X direction. The excitation frequency was swept from 10 Hz to 270 Hz in 30s, while the amplitude went from 100N (the shaker maximum value) to 50N, depending on the structure compliance. It has been noticed that the linear optical encoder, placed aside the linear guide ways, wasn’t able to detect any motion exceeding its resolution of 0.1 Pm: the available force level and excitation frequencies weren’t able to provoke sliding.