A Malfunction Monitoring Technique in Drilling Operations
An on-line technique is proposed to monitor the drilling faults. The spindle motor current is found to vary with the drilling load, and it is used as the basis for the development of the monitoring technique. The current measured by a current transformer is preprocessed by a full wave rectifier and a 20 HZ bandwidth low pass Butterworth filter. Based on the common trend depicted in the resulting signal two borderlines defining the abnormal operating conditions are generated. Both of the malfunctions occur progressively and instantaneously in drilling operation can be detected. A promising result of more than 80% success rate is obtained by the combined application of these two monitoring lines in actual tests.
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