Heyns S., Sambayi P.

Various researchers have investigated the use of torque measurements to assess drill condition on drilling machines. Although it has been established that such measurements could in principle be used, torque measurement has however not yet found its way into industry as a standard drill condition monitoring method, and drill bits are still often replaced non-optimally. Some of the reasons for this relate to factors such as the inconvenience of using telemetry for drill based strain sensors on production machines and poor signal-to-noise ratios. In this work we compare the use of strain gauged based torque measurements via telemetry to the use of the instantaneous angular speed (IAS) of the spindle for drill condition monitoring. The IAS was in this case measured using a digital encoder that gave 1024 pulses per revolution. It was shown this approach could generate diagnostic information similar to the torque measurements, without the complication of telemetry. In addition it was also shown that simplifying the angular speed measurement to a single pulse per revolution, still lead to useful diagnostic information, and holds promise for diagnostic systems that would be practical to implement.