Study On The Mechanism Of Chatter In CNC Heavy Cutting

The dynamic and static performance of CNCHT (Computer Numerical ControlHeavy Cut Machine Tool) is one of the most important factors that affect themachining efficiency. Improving the cutting performance and machining efficiency ofCNCHT has been pursued by human beings for a long time. This paper analyses the characteristic and its stability factors of common heavycut process at first, it also points out the defect of traditional chatter model andestablishes a new model which has no steady error, the new model is more suitable foranalyzing CNC heavy cut. Later, the limit cutting width that affects the stability ofCNCHT is resolved by many methods such as algebra criterion, computer simulation . Correcting the loops of CNCHT 's servo system has an effect on the dynamic andstatic performance of machine tool. Based on the introduction of engineeringcorrection, this paper emphasizes the research on current loop control which is basedon the state feedback and resonance of CNCHT, it also provides a new method forengineering correction. Simulation and experiment show: (i) The current loop basedon state feedback can improve the system's tracing performance and robustness. (ii)The resonance frequency of CNCHT is not only decided by natural frequency ofmechanism but also decided by natural frequency of speed loop. Selecting reasonableparameters of servo system and mechanism can enlarge bandwidth and avoidresonance in machine tool. Since dynamic cutting process of CNCHT is a mechatronical control system, asit has some uniform chatter rules of common heavy cut, it also differs with commonheavy cut. The paper establishes and analyzes the mathematics model of dynamic cutprocess in CNCHT, simulation shows that the factors which affect the stability ofCNCHT not only include vibration mass, overlapping coefficient, cut stiffness ofcommon heavy cut, but also include the parameters of servo system. As to adapt the time-varying, big disturbance, nonlinear in CNC heavy cut, thepaper introduces fuzzy control P adjuster in position loop at last. Simulation showsthat servo system based on fuzzy control has better dynamic characteristic androbustness, it can also enlarge the limit cutting width and improve the ability ofdisturbance suppression.