Research On Mechanics Properties And Control Strategies Of Closed Hydrostatic Guide-way Of CNC Gear Hobbing Machine

With advantages of high precision and stiffness，lower wear as well as long servicelife， the hydrostatic guide-way is widely applied in the field of CNCmachine．Hydrostatic guide-way，of which mechanical properties can directly affect thereliability of running，lifetime，and economic indicators of the whole machine，is oneof the important components of the rotary table of CNC gear hobbing machine．With thedevelopment of modern industry，the hydrostatic guide-way technology is significant tosupply the much higher requirement of high-precision， high-speed of CNCmachine．The closed hydrostatic guide-way has been widely used in rotary table ofCNC machine because of its strong unbalance load capacity and adaptability.Hydrostatic guide-way，of which bearing capacity and stiffness as well as operatingperformance are mainly depended on its oil film thickness．However，during theworking process of closed hydrostatic guide-way of constant flow，the oil film thicknessis unstable withstand the external loads，which affect the carrying capacity and filmstiffness of hydrostatic guide-way．In the constant flow supply system，the mechanicalproperties of the hydrostatic guide-way is related to the structure of the oil chamber andoil flow without considering the influence of the oil temperature on viscosity．Firstly，based on the lubrication theory and the principle of the hydrostatic bearing and fluidmechanics，a series of mechanical properties equations of closed hydrostatic guide-wayof constant flow are established，including flow equation，pressure equation，carryingcapacity equation，stiffness equation when it suffers from heavy loads and torquerespectively．Based on the above equation，deeply theoretical study are conducted inthis paper from the two aspects of the structure of the oil chamber and the oil flow．In terms of the structure of the oil chamber，the influences on the oil filmthickness，carrying capacity and the oil film stiffness by the effective bearing area of oilchamber and the effective bearing area ratio of the opposite guide-way and the mainguide-way are analyzed withstand the loads or torque．The optimal range of theseparameters is pointed out，which provides valuable reference for designer．As the oil flow is constant，hydrostatic oil cavity pressure and oil film thicknesschanges as the external applied load changes．Therefore，to ensure that the oil filmthickness remains design thickness and the film stiffness tends to infinity，a controlscheme is proposed．In order to control oil film thickness by changing the oil flow under different load，this control system consists of controller，actuating motor，hydraulicpump and closed hydrostatic guide-way，of which the control principle is verified bytheoretical calculations．To further analyze this control system，a simulation model and a PID control areestablished Moreover， the simulation has been done in Matlab/Simulinkenvironment．Comparing the simulation results with experimental test results withoutcontrol system，it is shown that the film thickness remains almost as the design filmthickness by control system and film stability is greatly improved．Based on the research finding of this paper，the problem that the oil film thicknesschanges unstably as load changes is solved effectively，which improves the bearingcapacity and rigidity of the closed hydrostatic guide-way of constant flow and indicatesthe significance of this study．...