BASIC RESEARCH ON LAPPING PROCESS WITH INTRODUCING A METHOD OF ACOUSTIC AND BIVRATION MONITORING

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In this research, we proposed and established the monitoring technique of lapping process by detecting the power level of small acoustic and vibration signals, clarifying why the vibration frequency is generated, and specifying the frequency for monitoring.1. A conical horn type and a cylindrical type jig as lapping weights were designed to detect low level and high frequency oscillating signal precisely. The former was designed mainly to amplify the vibration and the latter was to avoid the resonance. An acceleration pick-up or a piezoelectric sensor was mounted on the top of work to detect the signal up to the frequency of 100 kHz.2. When a model lap with a work was vibrated vertically without rotating, the characteristics of oscillation of the jig was that of typical second order system with the natural frequency of 1.5 -2 kHz. We measured the diameter distribution of abrasive grains and estimated the number of grains that might be concerned with the contact. Based on the Hertz's theorem, the elastic deformations of the contact portion were regarded as springs and the formulation of the natural frequency was obtained. In the case that the lap was rotating slowly, the situation seemed wholly changed and the frequency of the work vibration spread to 0.5 - 4 kHz , because the condition of contact was varied every moment.3. The frequency distributions of generated oscillation under various process conditions shows that the peak frequency that connects to the state of processing exists within the range from 0.5 kHz to 2 kHz and the peak value in dB has a linear relation to the surface roughness of the work.