A study of the influence of superimposed low-frequency modulation on the drilling process

A preliminary investigation of the effects of low-frequency modulation of the force in drilling has been completed. Important changes occur in the drilling of aluminum with the imposition of modulation at frequencies below 200 Hz. The effects depend on the amplitude of the modulation and the relationship of the frequency of modulation f(p) to the frequency of rotation of the drill f(d). When f(p)/f(d) is an even integer, the modulation introduces no significant effects in the force, torque, or chip morphology. When f(p)/f(d), is an odd integer, the average drilling force decreases, and a large dynamic component of force and torque is seen with a frequency dependence f(p). For peak-to-peak amplitudes of vibration that are greater than one-half of the drill feed/rev, the chips are broken. A simple explanation of these effects is provided. (C) 1998 Elsevier Science Inc.