Control of self-excited vibrations in face milling with two-rim mill

Abstract

The paper provides an overview of self-excited vibration damping methods for face milling. The main source to maintain and develop self-excited vibrations is the mechanism of their regeneration. To suppress it, two methods are currently actively used: tools with variable tooth pitch and cutting speed modulation. A combination of these methods was used to develop a vibration-resistant face mill with two-rims provided with alternating teeth and connected with adjustable stiffness by spring. The spring also allows a variable pitch of adjacent teeth to be adjusted. During cutter operation, the elastic connection of the rims creates difference in the cutting speed of adjacent teeth, which suppresses regeneration of self-excited vibrations and decreases their amplitude. The self-excited vibration damping efficiency of the proposed mill was determined by comparing its operation with that of a conventional mill in the same conditions of roughing a steel workpiece. The dynamics of the milling machine technological system during operation of both tools was studied using a simulation method. It was found that the conventional mill cannot be used under cutting conditions accepted in the study because of increased vibrations of the technological system elements. On the contrary, a two-rim mill provides almost quiescent processing conditions at appropriate values of the elastic connection stiffness of rims and their relative angular displacement. The settings of the two-rim mill were determined with respect to a moving rim and a spindle with another rim as a dual-mass system with two degrees of freedom.