Monitoring drilling wear state using vibration based diagnosis

Determining when the tool shall be replaced is critical in automated drilling processes. Monitoring drilling wear state helps to take the decision. This could prevent tool breakage and significantly reduce machine downtime. Currently, the tool is replaced after a predetermined number of machined workpieces. This method is not satisfactory due to a wide spread for tool life. Drill wear is a progressive process. It takes place at the contact tool-workpiece with elevated temperatures at the interface. It is a stochastic process for many reasons: bluntness of the chisel edge, a dead centre, a great difference in cutting speed between the centre and the periphery. A wearing diagnosis method in drilling has been developed in the frame of the ESPRIT project 2349 "Fault tolerance in the control and management of production systems." This method is based on vibration measurement during the cutting operation and a pattern recognition technique for classification.<>