Researches On Dynamics Optimization Of High Precise Cylindrical Grinding System

Vibration is an unfavorable dynamic phenomenon encountered in grinding operation. It influences the quality parameters of work pieces surface spoiling its dimension precision and surface roughness, resulting in surface waviness. As the cooperation with XX CNC Co.Ltd. in the "Research on dynamics optimization of MGB1412×250 high precision cylindrical grinding machine ", the grinding vibration suppressing especially chatter suppressing is analyzed. Structure dynamic analysis and stability predication is necessarily used to restrain vibration especially chatter and improve precision of grinding work pieces. Therefore, a new conception of stability optimization based on stable grinding of high production efficiency and precision is used in the whole life cycle of the design, manufacture, inspection, machining operation and maintenance.Sub-structure dynamic method is used to analyze grinding wheel- principal axis system, lathe hedd, tail stock, grinding wheel stock, saddle, workbench and lathe bed etc. The simplicity of analyzing its dynamic characteristics and the precision of numerical value calculation is guaranteed by dividing complicated grinding machine into pieces. The boundary conditions are determined by dynamic experiments, based on frequency-response function, the equivalent dynamic parameters of stiffness and damping are recognized which are compared and modified by the boundary conditions obtained in dynamic experiments. The numerical value calculation results used by sub-structure dynamic methods and boundary conditions recognition technique agree well with modal experiential results which lay the foundation of structure dynamic optimization.Stability investigation is based on displacement feedback regenerative chatter principle. Considering work piece regenerative chatter and grinding wheel regenerative chatter, the plunging grinding closed loop system dynamic model is set up. The traverse grinding dynamic model is also set up with the simplified of plunging grinding to the sum of plunging grinding. Using frequency-response function which is expressed by grinding parameters and structure parameters, the characteristic equations are calculated. The predicting method of stability criterion with respect to the rate of chatter waviness increase is proposed. In this way, the influence of grinding parameters to grinding stability is portrayed.Experiments of modal analysis are designed and carried out to investigate and validate the dynamics model, stability theory. With the modal, racing and grinding experiments, the nature frequencies calculated by numerical value calculation of the whole grinding machine and its sub-structures is validated. The matching of grinding parameters designed in racing and grinding experiments are used to validate stability theory. Experiments are also used to diagnose the experimental grinding machine, the faults leading to surface waviness as well as vibration eliminate methods are pointed out.Dynamic optimization technique in cylindrical grinding is based on structure dynamics, stability analysis and dynamic experiments with technique of structure dynamic modification and grinding parameter modification. As an example, dynamic optimization technique is used for MGB1412×250 high precision cylindrical grinding machine to improve its dynamic characteristics.