VIBRATORY ACTIVITY INVESTIGATION OF GRINDING MACHINE ELECTRIC SPINDLES

The purpose of this work is to support dynamic properties of spindle units in grinding machines. For this there are problems under solution for the definition of the origin of the constituents in the spindle unit vibratory activity by means of the linear increase of electric spindle rotation frequency, obtaining and analyzing a vibratory acceleration signal for the possibility to determine a preload. The vibratory acceleration signal was investigated through a spectrum analysis method. A scientific novelty of investigation consists in the substantiation of possibility to determine a preload by means of the spectrum analysis of a vibration acceleration signal at the linear increase of spindle rotation frequency that is at starting. It gives, in its turn, a possibility for the automated estimate of the spindle unit state before cutting beginning. In the experimental way there are obtained temporal realizations of the vibratory acceleration signal at different efforts of the preload. A high-speed grinding motor-spindle is as a basic element of the bench, which was investigated through the methods of testing diagnostics in the operation. In the bench design there were made some alterations. The bench was supplemented with the systems essential to support motor-spindle full operation, in particular: with systems of lubrication, cooling and drive control. There was revealed a large number of harmonics multiple to 50 Hz, which tells of the connection with the frequency of power supply circuit. Their coincidence with the own frequencies of the spindle unit results in the considerable increase of their amplitudes. To increase dynamic quality one should avoid the cases of the coincidence of switching frequencies and circuit harmonics with own frequencies of the electric spindle. It is also necessary to bring a form of power voltage to a pure harmonic oscillation to decrease the impact of a drive electromagnetic field upon dynamic characteristics of the spindle unit.