Mechanistic model for drills with double point-angle edges

This article introduces a mechanistic model for predicting thrust force and torque during the drilling process of aluminium alloy Al 7075-T6. The drill used is specially designed to machine aluminium alloys used in aerospace applications; it is a tool with double-point angle edges, specially designed to avoid part distortion at the drill entrance into material. The mechanistic model requires obtaining specific cutting coefficients; those coefficients are adjusted following two methods. On the one hand, they are adjusted with regard to the geometrical parameter Z coordinate of the discretized points of the drill main edge. On the other, they are adjusted with regard to cutting speed and inclination angle, which vary along the main edge. The specific coefficients are obtained from a series of experimental tests in which the mechanistic model is applied in a reverse way.The model is validated in a wide range of cutting conditions, both within and outside the range of cutting conditions used, to obtain the coefficients. Results show close correlation between the models and the experimental data in the first case (less than 15% errors) and error between 20 and 35% in the second case.

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