Modeling of non-linear cutting forces for dry orbital drilling process based on undeformed chip geometry

Abstract

The application of dedicated cutting tools with complex geometric structures in the orbital drilling process has promoted the rapid development of this new technology within the aircraft industry. Based on the orbital drilling kinematics, the complex machining path generated by the tool, combined with the large number of non-uniform and irregular chips formed under the varying cutting conditions, makes it a challenge to model the cutting force for the orbital drilling operation. This paper proposes the steady machining stage in orbital drilling as a representation of the whole machining process. During the chip formation period at this stage, the undeformed chip geometries produced by each tooth are analyzed and described. The undeformed chip thickness and the width of cut are then calculated. Based on these instantaneous chip geometries, a non-linear cutting force model for the orbital drilling process can then be developed. This experimental study on the orbital drilling process is conducted using a TC4 alloy, with the aim of calibrating the special cutting force coefficients using the average cutting force method, and further validating the cutting force model. The results show that this model can be used to predict the cutting force generated in the half rotational period in the steady cutting stage of the orbital drilling process. Furthermore, it can be used to guide the optimization of machining parameters and the structural design of the dedicated cutting tool by analyzing the relationship between the predicted cutting forces and the feed rate, with the aim of improving the final quality of the borehole.