Evaluating tool wear by measuring the real-time contact resistance

A method is proposed to diagnose wear and to determine the replacement schedule for a working end-mill cutter. Changes in the contact area between a working end-mill cutter and the workpiece during a milling process lead to a real-time variation in the contact resistance. Measuring the real-time contact resistance using a micro-ohm meter and a GPIB (general-purpose interface bus) interface control card allows the wear in a working end-mill cutter to be determined. Real-time contact resistance values for a working end-mill cutter are measured and recorded every second. The experimental results demonstrate that when the milling cutter operates continuously for about 20,000 s, the contact resistance decreases to about 25% of the original value for the brand new state. This method can be used for the future design of milling machines. If the value of the contact resistance for a working end-mill of the same type approaches this value, the cutter should be replaced in order to maintain efficient machining.