Research On Chatter Stability Of Oblique Turning Processing System

Lathe machining is a very common machining method in mechanical processing. In turning operation, the phenomenon of affecting the productivity and efficiency seriously in machining is unstable cutting, which we usually called chatter. Chatter is a strong relative viberation occuring between tool and workpiece in cutting process, it belongs to self-excited viberation.The occurrence of chatter can reduce the life of cutter, size accuracy and surface quality of workpiece. Chatter happen or not depending on cutting parameter be selected in the steady limits. However, chatter often occurs because the geometry sizes of cutting tool and workpiece are changing. Chatter is a vibration with small amplitude and high frequency, in order to avoid occurrence of this kind of vibration, we must choose reasonable cutting parameters during the machining process, so we bring in "stability lobe diagrams" to avoid this occuring of chatter; it’s important and significant for improving the performance of machine tool.This paper is dedicated to build a new chatter model to predict the maximum limit of stability in cutting process. Most previous chatter models are established on orthogonal turning and only one direction is considered; besides, the vibration equation is too simple to predict in the actual cutting conditions.First of all, this paper introduces the geometric relationships of oblique turning and discusses the mechanics theory of3D oblique cutting in the actual cutting processing, and gives cutting force coefficient predicting formula of oblique cutting in the three directions.Then, according to the relations of cutting force on three directions, chatter system is expressed into vibration equation on two degrees of freedom. Next, we get modal parameters of tool system through hammering test. Plus considering of dynamic coupling between two degrees of freedom vibration system, we change the vibration of Y direction into Z direction by their geometric relations to establish chatter model and utilize the analytical method to calculate stability lobe diagram in frequency domain.Finally, We adopt numerical simulation to the model, test chatter theory combining with chatter test, identify the best spindle speed and the accordant best cutting depth under particular cutting conditions.