Comparing orthogonal force and unidirectional strain component processing for tool condition monitoring

Signal processing using orthogonal cutting force components for tool condition monitoring has established itself in literature. In the application of single axis strain sen­ sors however a linear combination of cutting force compo­ nents has to be processed in order to monitor tool wear. This situation may arise when a single axis piezoelectric actuator is simultaneously used as an actuator and a sensor, e.g. its vibration control feedback signal exploited for monitoring purposes. The current paper therefore compares processing of a linear combination of cutting force components to the reference case of processing orthogonal components. Recon­ struction of the dynamic force acting at the tool tip from signals obtained during measurements using a strain gauge instrumented tool holder in a turning process is described. An application of this dynamic force signal was simulated on a lter­model of that tool holder that would carry a self­sensing actuator. For comparison of the orthogonal and unidirectional force component tool wear monitoring strategies the same time­delay neural network structure has been applied. Wear­ sensitive features are determined by wavelet packet analysis to provide information for tool wear estimation. The proba­ bility of a difference less than5percentagepoints between the ankwear estimation errors of abovementioned twoprocess­ ing strategies is at least 95 %. This suggests the viability of simultaneous monitoring and control by using a self­sensing