Experimental Estimation Of Process Damping During Cutting Based On Active Excitaion Modal Analysis

The chatter which occurs during cutting process has a direct impact on the machining quality of workpiece, production efficiency and life of machine tool. Therefore it is necessary to analysis and predict the chatter during cutting process. The machining stability is not only related to the structural damping of machine tool and the process damping generated during cutting process. The process damping have significant effects on the machining stability when the cutting speed is low. Therefore the accurately identification of the process damping has important significance for analyzing and predicting of the machining stability. In this paper, an experimental approach was presented to identify the process damping based on Active Excitation Modal Analysis.Firstly, the causes of the process damping was analyzed and cutting dynamics model which includes a process damping coefficient was established in this paper. Due to the regenerative effect which leads to the inaccurate identification of process damping, interrupted cutting was used to eliminate the influence of the regenerative effect and the validity of the proposed approach was verified theoretically.Random interrupted cutting based on Active Excitation Modal Analysis was presented, the random pulse cutting force was generated to excite the structure of machine tool by cutting through the specially designed workpiece, and the dynamic parameters was identified by the response signal. By comparing the experimental results of random interrupted cutting and normal cutting with impact test, it proved that the random interrupted cutting method could eliminate the influence of regenerative effect.According to the characteristics of turning, a random multi-tooth cylindrical workpiece was designed to meet the requirements of Active Excitation Modal Analysis. The structure damping and total damping of machine tool machining system was obtained by impact test and random interrupted cutting test, and the process damping of the system was identified under different cutting speed.The influence of process damping on the cutting stability was researched by comparing the predictions of cutting stability which consider the process damping with the results of traditional cutting dynamics model, and the prediction results are verified by chatter experiments finally.