Modeling and characterization of an electromagnetic system for the estimation of Frequency Response Function of spindle

International audienceAn electromagnetic system developped to measure the quasi-static and dynamic behavior of the machining spindles at different spindle speed is presented in this paper. This system consists in four Pulse Width Modulated amplifiers and four electromagnets to produce magnetic forces of ±190N for the static mode and ±80N for the dynamic mode at up to 5kHz. In order to measure the Frequency Response Function of the spindle at the tool tip, the precise prediction of the applied load is required. A dynamic force model is proposed in order to obtain the load from the measured current in the amplifiers. The model depends on the exciting frequency and on the magnetic characteristics of the system. The predicted force at high speed is validated with a specific experiment and the perfomance limits of the experimental device are investigated. The Frequency Response Functions obtained with the electromagnetic system are compared to a classical tap test measurement at 0 rpm

Experimental Investigation of the Dynamic Behavior of High Speed Machining Spindles with an Electromagnetic Excitation Device

International audienceFrequency Response Function measurements are carried out on two different industrial HSM Spindles rotating up to 24000rpm and powered from 40 to 70kW. An electromagnetic excitation device capable of applying a dynamic force to ±80N at 5kHz is used to perform the experiment. Measurements are made on four points by two displacement sensors and two accelerometers. A specific signal processing method that uses the cepstrum of the signal is applied to remove harmonics of the rotation in the signal. Variations of the dynamic behavior of the spindles with speed are observed and analyzed