Study On Rotating Precision Degradation Mechanism Of Precision Spindle System

The precision spindle system is the core component of CNC machines and the deterioration degree of spindle system performance will directly affect the quality of work pieces. The rotating precision changes of spindle system are affected by bearing wear, fever, vibration, noise and other factors in the CNC machine operation process. Study of the spindle system rotating precision degradation mechanism can get a general law that during the service period, the machines’ performance gradually deteriorates, and ultimately it can’t complete required functions. Researches on rotating precision degradation mechanism are carried out based on high speed motorized spindle and CNC machine spindle system.Determine the degradation characteristics. The factors which affect the rotating precision of the spindle system are analyzed, and the average radial error of spindle system and axis orbit are selected as the indicators to measure the deterioration of the precision of spindle system. The average radial error represents the average radial amplitude. The axis orbit, as the output of the whole spindle system, is the fusion of wear, thermal deformation, vibration and noise of the spindle system, which can fully reflect the performance of the spindle system.Analyze the bearing degradation mechanism from statics, dynamics and thermal aspects. Bearing is the key part of the spindle system and bearing degradation situation decides the state of the spindle system. In the part of statics analysis, the formulas of curvature, curvature difference, stress and strain are deduced. From the analysis of stress, strain and subsurface stress, the inner rollaway of bearing suffers the maximum stress and deformation. In the part of dynamics aspects, centrifugal force and gyro torque are studied. When the bearing size is confirmed, the centrifugal force and gyro torque can be dramatically reduced by using the ball made of low density ceramic material, so as to reduce the friction heat and put off deterioration. In the thermal analysis part, when the bearing maximum static load and maximum rated load, the bearing inner ring heats most, ball second, outer ring least.Using manifold learning algorithm to extract the weak features of the axis orbit of the spindle system, the identification model of the spindle system degradation state is established. The high dimensional feature space is set up by the feature of the space of the axis orbit, and the low dimensional manifold of the axis trajectory is extracted from the manifold learning algorithm. Through the rotor test, simulating the degradation process of the spindle system from normal state to unbalance state and the structure of the low dimensional manifold with different degradation states of the spindle system is established. Manifold learning algorithm of LTSA algorithm and Laplacian algorithm can effectively distinguish orbit low dimensional manifold features of normal, unbalanced, touch the friction state of spindle system, and identify and classify different states of deterioration.The rotating accuracy deterioration of the spindle system is studied, and the rotating accuracy deterioration model of the spindle system is established. Based on CJK1630 numerical control machine tool, the spindle loading device is designed and manufactured. Build the thermal deformation test bench and dynamic error test rig of the spindle system. Real time on-line measurement of thermal distortion and average radial error of the spindle system are realized. The thermal deformation tests of the spindle system, the average radial error with time, the temperature degradation test, the no-load, the load average radial error along with the speed of the test are carried out. Through the average radial error fitting with the model, the linear law of rotating accuracy degradation of the spindle system is determined.