Study On Tilted Shafting Bearing Characteristics Of Hydrostatic Turntables For Lapping Machines

Lapping machines are mainly used for precision and ultra precision machining inoptical components, aviation, automobile, die, gems and various hardware industries,in particular, they have an extensive application prospect in optical componentsindustry. Turntables are the core component of lapping machines. Compared withexisting turntables supported with rolling bearings, hydrostatic turntables haveobvious advantages of small friction and wear, high rotation accuracy, high absorbingvibration and damping, and long life. Previous research on hydrostatic turntables islimited to non tilted shafting. However, hydrostatic turntables will more or less tilt inthe actual operation. The bearing capacity is changed by the tilt of hydrostaticturntables and even it leads to scratch of support elements in hydrostatic turntables.Therefore, it is necessary to study tilted shafting bearing characteristics of hydrostaticturntables for lapping machines.Closed type hydrostatic turntables are developed and their invention patents(CN201220388052.7) are applied for. Contrasted to open type hydrostatic turntables,they have advantages of high stiffness and strong resistance to overturning moment.The method of equivalent oil film thickness is proposed. The proposed method isderived from the infinitesimal integral method. Two methods are used to calculatetilted oil film characteristics of thrust and journal bearings in hydrostatic turntables.The mechanical model of closed type hydrostatic turntables in which tiltedcharacteristics of bearings can be reflected is built combined with concrete structure.Comparison between bearing behaviors in close and open type hydrostatic turntablesis carried out. The tilted oil film flow filed of thrust and journal bearings inhydrostatic turntables is also computed by CFD. The effects of structural and workingparameters on flow field characteristics of tilted oil film are studied by CFD. Theproposed method is verified by comparison with the infinitesimal integral method andCFD. The efficiency of the proposed method is significantly improved withoutsacrificing accuracy and it can overcome the deficiency of low efficiency in theinfinitesimal integral method and CFD. The influences of various factors on the tiltedoil film characteristics of thrust and journal bearings in hydrostatic turntables areinvestigated by the proposed method.An experimental platform of closed type hydrostatic turntables is built by Hunan Hicam Spindle Science and Technology Co., Ltd. Oil film thickness, stiffness andflow rate of bearings are measured on the experimental platform. It is shown that theclosed type hydrostatic turntable can run smoothly and has good overall performance.The experimental results are also in good agreement with theoretical ones. Thevalidity of the proposed method is confirmed by simulation and experiment. Theproposed method and related research results have important referenced value for thedesign and the optimization of structure and working parameters of hydrostaticturntables.