A passive adaptor to enhance chatter stability for end mills

Abstract

A design procedure is suggested in this paper to enhance the chatter stability of an end mill cutter. Tool chatter is a well recognized self-excited vibration problem where the excitation force is the cutting force required to machine a workpiece. The cutting force magnitude is proportional to the thickness of the chip removed from the workpiece. The thickness of the chip, on the other hand, is affected by two distinct sets of events, namely, the instantaneous oscillations of the tip of the cutter and the undulations left on the surface from the earlier passes of the cutter. Hence, the excitation force, which is the cause of the oscillations, feeds on the oscillations. In this investigation, an end mill is simplified to be a beam cantilevered from a relatively rigid spindle. A local structural modification technique of the authors is then applied to this beam to suppress its proneness to excessive resonance vibrations. An add-on passive adaptor is developed for this purpose. Numerical simulations with random tip excitation and experimental verification with a scaled model are discussed. Suggested designs promise to enhance the chatter stability of a cantilevered cutter. Cutting tests are being planned for the next stage of work.