VIBRATION SIGNAL MEASUREMENT - AN ALTERNATIVE FOR DESCRIBING MECHANICAL GRINDING PROCESS

Grinding of minerals by mechanical means emits a strong noise signal, which varies with the changes of the operating state. With the goal of applying the phenomenon as a monitoring techniques in grinding, the v ibration signal from a laboratory scale batchwise ball mill was measur ed and processed under different grinding conditions. To build up a '' stereo picture'' of the milling state, the source vibration was picked up by means of an accelerometer (mechanical) and a microphone (acoust ic pressure). The time-domain vibration signals picked up from grindin g were transformed into frequency-domain spectra. The spectrum was div ided into three sub-frequency bands consisting of one or more signific ant peaks. The power spectra were illustrated and compared by 3-D illu stration. Larger differences between dry and wet grinding were found f or an acoustic signal than for the mechanical vibration signal. It was found that the first two principal components' accounted for 98% of t he total variations of the mechanical vibration signals. The relations between the principal components and the parameters of measurement se tup were established by multiple regression.