Low-frequency modulation-assisted drilling using linear drives

Abstract

A new machine tool based on linear drive technology has been developed for low-frequency modulation-assisted drilling. The linear drive utilizes a novel design for generating continuous drill feed motion with a superimposed low-frequency modulation of up to 400 Hz without the use of secondary actuators. The frequency characteristics of the drive are such that a wide variety of drilling conditions can be systematically explored. Results pertaining to torque, thrust and controlled chip breakage when drilling ductile aluminium alloys are presented to demonstrate the attractive features of modulation-assisted drilling using linear drives. It has been shown that the application of a superimposed modulation of the appropriate frequency and amplitude produces consistent chip breakage, thereby facilitating the drilling process. Furthermore, under these conditions, the mean torque and mean thrust are decreased in comparison with conventional drilling. The frequency and amplitude conditions for which such beneficial effects are observed can be predicted using a simple model for chip formation and forces in modulation-assisted drilling.