SIMULATION OF THE DYNAMICAL BEHAVIOUR OF AN AUTOMATIC BAR FEEDER UNDER VARIABLE OPERATING CONDITIONS

摘要

The dynamical model of an automatic bar feeder, consisting of four different substructures, was developed and numerically implemented to obtain the natural frequencies and mode shapes of the system under variable operating conditions. This machine is commonly used to feed automatic lathes whenever high production rates are required. Since variable section and length, strongly misaligned rotating bars are commonly used, severe vibrations may occur at some operating conditions, so that the lathe cutting process may be strongly affected by them. Previous knowledge of the whole machine dynamical behaviour under variable operating conditions is thus required, to basically help the user to set a correct cutting process plan. To obtain the dynamical modal model of the system, i.e. eigenfrequencies and eigenshapes, a parametric, finite element model of the rotating bar was achieved, and elastically coupled with other substructures, namely the frame, the bed and the bearings. The modal model of these structures was obtained by experimental, polyreference modal analysis. Details of the substructuring technique, as well as of the numerical and experimental approaches adopted, are reported in the paper.