Study On Friction Characteristics Of Sliding Joint Surface Of High Precision NC Feed System

High precision machine tool feed system is prone to vibration along the feed direction when starting,which seriously restricts the machine tool movement accuracy and reduces the machining quality of parts,and the existence of nonlinear friction between contact surface is the main cause of vibration.In order to reduce the frictional vibration phenomenon and improve the stability of sliding joint surface.Based on static and dynamic friction models,this paper explores the causes of frictional vibration of moving joints,and investigates the influence of the change of contact conditions on the friction characteristics of the interface.Based on the simulation and experiment of textured surface,a method to reduce the friction vibration of sliding joint surface of high precision NC feed system is proposed.A simplified single-degree-of-freedom system model is established for NC feed system,and the static and dynamic friction models are introduced respectively for numerical simulation.The dynamic response of the feed direction of the system is analyzed by using the phase diagram and the time-domain diagram.System stability analysis based on Routh-hurwitz criterion.It is found that the increase of damping and stiffness in the feed system weakens the frictional vibration to some extent,but the frictional vibration between the sliding joint is mainly due to the negative gradient effect of friction force.The friction characteristics of the sliding joint surface with material,relative sliding velocity and acceleration were studied by pin-disk experiment.At the same time,it is found that small surface roughness can reduce the steady friction coefficient and expand the fluid lubrication zone.But the oil storage area can promote hydrodynamic lubrication to some extent.In order to amplify the advantages of surface groove area,improve interface lubrication,and then reduce negative gradient effect,the contact surface is textured.Based on the fluent simulation results,experimental specimens containing cylindrical surface texture were designed and manufactured.The experimental results show that the difference between the friction coefficient in the boundary lubrication region and the steady friction coefficient decreases obviously and the negative gradient friction effect is weakened when the texture parameters are R=0.025,S=0.15 and S=0.1.Finally,the experimental results are imported into ADAMS software for joint simulation.The simulation results show that the addition of the surface structure can effectively reduce the vibration amplitude and the vibration range in feed direction.It is verified that the texture surface has a weakening effect on the frictional vibration.The research methods and conclusions in this paper have certain reference value for improving the motion stability of the sliding joint surface of NC feed system and reducing the nonlinear friction vibration phenomenon.