Finite Element Coupling Analysis And Experimental Study On The Static Characteristic And Thermal Performance Of The Aerostatic Motorized Spindle

High speed, precision, ultraprecise machining technology is an important trend of advanced manufacturing engineering, and the high speed, high precision motorized spindle is the technical precondition and foundation and the improvement of its speed and rigidity is very hot to research. One of the contactless support units with the air as the lubricating medium, the air bearing, due to its proper homogenization, can enable very gyration precision, moreover, and little friction and abrasion. Furthermore, its speed is very high and long service life can be achieved. However, the loading capacity and rigidity are much lower. The traditional aerostatic bearing motorized spindle is often applied in the occasion where the cutting load is not much large. As to these, it is important to discover the new way to improve the loading capacity and rigidity of the air bearing to extent its field form conventional high speed drilling, grinding to the high speed, high precision milling and turning.In this article, the high speed and high power aerostatic bearing supported spindle has been studied, firstly, the static air bearing is researched, where finite element method is applied and complete parameter three-dimensional entity model is built up, then the pressure distribution of the bearing is analyzed in the cases where its eccentricity is different, and capacity and rigidity of the air bearing is obtained. Based on this, kinetic pressure effect of the static pressure bearing is also analyzed, traditional design analysis which does not consider the kinetic pressure effect. And its design accuracy of the bearing is improved compared with the traditional method. What is more this way can be also utilized in the hydrostatic lubrication.On the base of the finite-element analysis of single aerostatic bearing, air-solid coupling method is developed to static characteristic analysis of full supported motorized spindle, overcoming the disadvantage of the classic method, which firstly get the characteristic coefficient of rigidity, damp ratio and so on, then elastic support equivalent is built up to model the spindle unit, that way, the fluid and structural interaction directly with bearing acting as support can possess higher precision.In addition, as to the heat affection of the heavy duty air static pressure spindle,the fluid and thermal coupling method is taken to analyzes the heat exchanging between the fluid and solid, so the thermal performance of aerostatic bearing motorized spindle is studied, avoiding the middle step of traditional method, that is from convective heat-transfer coefficient acquired by the empirical formula to applying the coefficient into the motorized spindle. It is proved that heat fluid method can achieve higher accuracy.Finally, the experimental set up has been built, and experimental verification of both static rigidity and thermal state character has been carried out. Results of the experiments indicated that both analytical procedure and the result are feasible.