Prediction Of Machining Chatter Based On FEM Simulation Of Chip Formation Under Dynamic Conditions

Machining chatter is an inherently important phenomenon that is affected by many parameters such as cutting conditions, tool, treatment, tool wear etc. Models for chatter prediction often ignore nonlinearities or introduce them through simple models for friction and geometry, especially the effect of chip-tool interaction on the occurrence of chatter is not investigated thoroughly. This paper presents a method for prediction of chatter vibration and for investigation of the effects of various conditions on the onset of chatter. In the theoretical simulation using nonlinear finite element analysis software Ansys/LS-DYNA to investigate the inter-relationship between the chatter vibration and the chip formation, mesh adaptation technique is used to move the tool inside the workpiece to form the chip in a variety of depths, researches on the effects of tool geometry e.g., nose radius and rake angle and clearance angle and friction conditions at the tool/workpiece interface have been carried out. Furthermore, based on Matlab/simulink, the stability diagram in terms of the radial depth of cut limit and spindle speed is figured. Time domain simulation is used to check out signals produced by cut force and structure vibrations, and to determine whether the occurrence of chatter.In order to obtain the Frequency Response Functions (FRF) of the cutter and work piece, a modal test setup, and to measure the chatter frequency a data acquisition and analysis system is used of CNC lathe. Stability lobe map obtained from simulations is compared with experimental data attained through orthogonal cutting tests. Reasonable agreement observed between the two sets of results demonstrates the effectiveness of the simulation approach. The results laid a foundation for the machine tool chatter suppression.