| Relative vibration between the tool and work pieces during metal cutting is distinguished as chatter which not only influences the processing quality but also reduces working life of the machine. Therefore, vibration in the course of working is a hotspot in manufacturing and a lot of research has been done by domestic and foreign scholars. Along with the maturation of numerical control technology, machine intelligence increases gradually with numerical systems that can deal with some overload or elevated temperature problems individually. However, few of the systems can handle the problem of vibration. Based on theoretical analysis of the previous studies, this thesis is to set up a machine chatter control system on the basis of milling stable region obtained through simulation of the VMC850E machining center in Shenyang Machine Tool Works. The main work in each chapter is as follow:1) This thesis summarizes researches about chatter theory and chatter suppression at home and abroad. It introduces and analysis structure of VMC850E machine. According of these, the writer determines how to do this research.2) This thesis establishes end-milling model according to Regenerative Chatter Theory; then through simplification of static cutting force and dynamic cutting force, it obtained a2-DOF motion equation with delayed entries. Meanwhile, the writer uses the experimental modal analysis to get modal parameters and resonance region.3) The mathematical model of end-milling serves as basis of the SIMULINK simulation model. On basis of response in the simulation model, this thesis provides the method of ensuring stability threshold. Besides, it is simulated controlling spindle speed to suppress chatter.4) This chapter establishes acquisition module for collecting signal of speed and vibration. Its hardware platform is based on suitable hardware, and software platform based on VB. This system can realize the function of observing vibration signals online and analyzing signals offline. 5) This thesis establishes a speed control module which is based on VMC850E’s electrical structure. In order to control spindle speed, it is necessary to change the ladder diagram and to edit a control program based on VB.6) The main work in this chapter is as follow:collecting vibration signals, reviving cutting force coefficient, improving simulation model, making a search of influence that operating conditions are working on thresholds.At last, there is a test on system for the time to judge chatter and the effect of suppressing chatter. After this test, it is confirming that the judging time is0.816and the effect is remarkable. |
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