Study and modeling of cutting phenomena influence on the vibration drilling performance
In the world of machining, due to new environmental constraints, the use of cooling is less and less recommended. For drilling operations, several techniques avoiding or limiting coolant have appeared during the last few years. Vibratory drilling is a new process which generates low frequency self vibrations in order to get a discontinuous cutting. Thus the low uncut chip thickness allows its natural evacuation. Vibrations are generated by a self vibratory drilling head which can be used on every kind of machine tool. This PhD work aims at modelling the cutting phenomenon in vibratory drilling. For each tool/material pair, it is possible to identify the cutting coefficients of the models thanks to an experimental strategy. The resulting models had then been introduced in a numerical simulator. This allows a virtual study of the dynamical behaviour of the drilling head with a fairly accuracy. Several experimental rounds of test show that the drill geometry, the cutting conditions and the drilling head parameters have a strong effect on the vibration's area. All the experiments have been done on an industrial application of crankshaft drilling. The optimization of this new process proved that long dry vibratory drilling is effective at an industrial scale. The drilling's quality is similar to the one of traditional drilling. The productivity is increased by five compared to the one of gun-drilling.