Analysis Of Friction And Wear Characteristics Of Slider Raceway Surface And Research On Grinding Process Optimization Technology

Rollers are used as rolling elements to form line contact with raceways in roller-type linear guide pairs.It has the characteristics of simple structure,low dynamic and static friction coefficient,high positioning accuracy,and good accuracy retention.It is widely used in machining centers,CNC machine tools,EDM cutting machine and a variety of heavy-duty modular machine tools.During the operation of the guide rail pair,wear is caused by the friction between the rolling elements and the raceway,and the guide rail pair accuracy will be lost due to the long-term wear.Consequently,the overall performance of the machine tool is deteriorated.The slider is one of the indispensable parts of the guide rail pair and the surface quality and friction and wear characteristics of its raceway inevitably affect the running accuracy and service life of the guide rail pair.Besides,the wear of the slider raceway is more frequently as the cyclic frequency of the contact between the slider raceway and the roller is much greater than that of the guide rail raceway.Therefore,the grinding process of the slider raceway surface is taken as the main research object in this article.From the perspective of the microscopic topography of the raceway surface,the quality evaluation,influencing factors research,friction and wear characteristics analysis and process optimization of the slider raceway surface are conducted to improvement of the surface quality and anti-friction and wear characteristics of the slider raceway.It is also of great significance to the maintenance of the running accuracy and the extension of the service life of the guide rail pair.First,a three-dimensional surface topography model of the grinding wheel used to grind the surface of the slider raceway is established.The dressing experiment of the grinding wheel and the experiment of grinding the workpiece by the grinding wheel are carried out.The confocal threedimensional profiler is used to measure the surface topography of the grinding wheel.Through the analysis and comparison of the probability distribution of the height of the abrasive particles on the surface of the grinding wheel before and after grinding,the critical protrusion height to judge whether particles actually participate in in the material removal process of the slider raceway surface is acquired.Based on this,the area threshold for identifying effective abrasive particles is determined.Image processing technologies such as the recognition,segmentation,marking,deletion of connected areas and the extraction,simplification,and fitting of effective abrasive particles' contours are applied into the scanning electron microscope image of the abrasive particles on the surface of the grinding wheel to extract the shape,size,distribution,and density of effective abrasive particles.And threedimensional morphology models of alumina abrasive grains and single crystal corundum grinding wheels are built.And the effectiveness and accuracy of the modeling method are verified through experiments from the perspectives of the distribution,density,size and quantity of abrasive particles.Secondly,the grinding motion trajectory of a single effective abrasive particle is analyzed,and the distribution model of the maximum undeformed chip thickness is used as an intermediate variable to establish a three-dimensional surface topography model of the slider raceway.Probability distribution function and DS evidence theory are used to quantify the wear amount of effective abrasive particles,and the cutting trajectory of effective abrasive particles is studied by combining with the specific grinding process parameters.The actual interference depth between the slider raceway surface and the single effective abrasive particle is determined based on extracting the protrusion height of the effective abrasive particle.At the same time,the deformation of the grinding wheel-workpiece and abrasive-workpiece contact area is quantified,and the actual contact arc length and effective cutting edge density in the current grinding area are obtained.On this basis,the distribution model of the maximum undeformed chip thickness is established.Because the surface morphology of the slider raceway is the cumulative effect of removing chips through the interaction of a large number of abrasive particles and the raceway surface,the maximum undeformed chip thickness distribution is like the replication of the grooves and protrusions in the raceway surface morphology.Therefore,the roughness profile of the raceway surface is obtained according to the chip distribution model,and a three-dimensional surface topography model of the slider raceway is presented through multiple loop calculations and the difference fitting in the vertical direction of contour.The correctness and rationality of the simulated topography model is verified by comparing it with the experimentally measured topography.Then,the characteristic information such as the height,width,and aspect ratio of the grooves,peaks and peak-valley structures are extracted according to the three-dimensional topography of the slider raceway surface.The friction and wear mechanism of the guide rail pair are analyzed,and the effect of the surface topography on the friction and wear characteristics of the slider raceway is investigated.The friction and wear test of the guide rail pair is carried out on the precision retention test bench of the rolling guide pair,and the influence of the geometric characteristics of the surface microstructure grooves,peaks and peaks and valleys on the dynamic friction factor is quantitatively analyzed,and the dynamic friction factor prediction model is established.At the same time,the contact deformation between the roller and the raceway surface is considered under different loads and the interference depth between the roller and the surface microstructure is calculated.And the true contact area between the roller and the raceway surface is determined,and the wear predictive model of the slider raceway is established by using the Archard wear theory and the model is verified through carrying out experiments.Then,the influence of surface microstructure geometric characteristics and wear conditions such as load,running-in stroke,running-in speed on the amount of wear is analyzed.Finally,the optimal grinding process is obtained by taking the surface grinding quality of the slider raceway and the grinding time in the fine grinding stage as the optimization goals.A threefactor and three-level grinding wheel dressing orthogonal experiment is carried out based on the dressing feed speed,dressing depth and linear speed of the grinding wheel.The range and variance are used to analyze the primary and secondary order and the optimal level of the influence of the dressing process parameters on the raceway's surface roughness to obtain the optimal combination of grinding wheel's dressing process parameters.Compared with the grinding wheel dressing process before optimization,the surface roughness value of the slider raceway ground by the grinding wheel with the optimal process parameters is reduced from 0.257 ?m to 0.199 ?m.The grinding depth,feed rate and grinding wheel's linear speed are used as the main grinding process parameters to carry out the single-factor grinding test of the slider raceway in the fine grinding stage,and the influence of each process parameter on the surface topography parameters and microstructure geometric characteristics of the slider raceway is analyzed.Taking the surface roughness as the dependent variable,the autoregressive moving average model is used to predict the data,and the interaction between the factors is considered to establish a multi-factor nonlinear function model of the surface roughness.Taking the surface grinding quality and the grinding time of the fine grinding stage as the optimization goals,the intelligent algorithm is used to obtain the optimal process parameter combination,and compared with the existing process parameters,the friction and wear characteristics of the optimized slider raceway surface are analyzed.Compared with the grinding process parameters used in the grinding workshop,the raceway surface obtained by the optimal process parameters with the grinding quality as the optimization goal not only reduces the roughness,but also reduces the geometric dimensions of the surface microstructure.And the dynamic friction factor is reduced from0.00604 to 0.00144,which can shorten the running-in time and improve the running-in quality during the wear of the guide pair.On the other hand,the raceway grinding time obtained by the optimal process parameters with the grinding time as the optimization goal is reduced from 12.6 min to 8.0min under the premise of meeting the factory standard(not greater than 0.4 ?m).The grinding efficiency is effectively improved.