Monitoring of Abrasive Waterjet Cutting and Drilling

In order to find a suitable way of on-line monitoring of the drilling and cutting process, the cutting head vibrations during drilling through various metal materials were measured with piezo-electric accelerometers attached around the cutting head. Three different types of experimental designs were carried on: drilling of different metals with the same thickness, operation with different abrasive mass flow rates without any workpiece and drilling of the same material with different types of abrasives. The most promising was the finding that inner dimension of the focusing tube is the most affecting parameter for cutting head vibrations. Continuous measurement of cutting head vibrations may therefore serve as an indicator of worn focusing tube. From the point of view of the on-line monitoring of drilling or cutting efficiency the sensors attached on the cutting head did not bring substantial benefit. No direct connection between dominant frequencies in vibration spectra and machined material was proved. The RMS of the vibration signal grows with the increasing mass flow rate and changes with different types of abrasives, but no significant direct relationship between abrasive characteristics and measured signal was discovered. Therefore, accelerometer placement on the workpiece appears to be much more promising from the point of view of drilling on-line monitoring.