Mechanism Of ELID Forming Grinding Bearing Outer Ring Raceway Based On Workpiece-cathode

High-precision bearing plays an important role in aerospace engines,high-precision machine tool,high-speed railway and high-precision apparatuses and instruments.Bearing raceway is working face of bearing.Its shape accuracy and surface quality affect accuracy,vibration and life of bearing.At present,processes of bearing outer ring raceway mainly include forming grinding and lapping.However,there are some problems in forming grinding,such as wheel blocking and dressing hardly.Ultra-precision lapping of bearing raceway is mainly used to remove grinding surface degenerating layer of bearing raceway and improve surface quality,which is not sensitive to shape and position accuracy.Manufacturing of high-precision bearing is restricted.Aiming at processing of high-precision bearing ring with varieties and small quantities,ELID forming grinding bearing outer ring raceway acting as cathode has been put forward.The problems such as easy blocking and hard dressing of grinding wheel are solved.Machining process of bearing ring is reduced.And precision machining of bearing raceway is realized.In this work,bearing outer ring is taken as a research object.Forming and state of oxide layer,effect of the state of oxide layer on surface quality and surface formation mechanism are revealed.Grinding parameters are optimized.Oxide layer has an impartant role in ELID precision grinding.However,it is difficult to measure state of oxide layer(thickness and compactness)in ELID forming grinding bearing outer ring raceway acting as cathode.The state of oxide layer and its influence on surface quality are revealed in ELID forming grinding bearing outer ring raceway acting as cathode by measuring state of oxide layer on surface of wheel sample in ELID forming grinding linear groove acting as cathode.The state of oxide layer was characterized by controlled current.An experimental study on ELID forming grinding bearing outer ring raceway acting as cathode was carried out.Effect of grinding parameters(wheel speed,workpiece speed,radial feed speed)and state of oxide layer on grinding force,surface roughness,waviness in grinding process was investigated.Mechanism of ELID forming grinding bearing outer ring raceway acting as cathode is revealed.There is ont only plastic flow of metal material,but also elastic deformation of oxide layer in ELID forming grinding bearing outer ring raceway.A new model for surface roughness based on plastic flow and elastic deformation of oxide layer was set up in ELID forming grinding bearing outer ring raceway acting as cathode.Moreover,it was verified by experiment.Experimental results show that surface roughness model has higher accuracy and better universality than theoretical model and empirical model.In order to obtain better surface quality,orthogonal test and extreme difference analysis were used to optimize process parameters of ELID grinding bearing outer ring raceway acting as cathode.A set of optimal parameters were obtained.After optimization,surface roughness Ra of bearing outer ring raceway reaches to 0.04?m and its waviness Wa reaches to 0.04?m.The results of this study not only have important scientific value for ELID grinding theory,but also expand processes of bearing outer ring raceway.Surface quality of bearing outer ring raceway is improved.It has an important theoretical significance and practical value for development of high-precision bearing.