Separated Aerostatic Bearings And Its Mechanism Of Error Averaging

Shaft is the key component of machine tools and rotating measuringinstruments, and it is an important factor of affecting the accuracy of processing andmeasurement. At present the main use of shaft structure is separated, and this existssome shortcomings, such as poor of process and difficult to adjust the gas filmthickness. In accordance with these problems, a kind of separated aerostatic bearingswas designed and research was taken on its error averaging mechanism. Mainresearch contents and solved problems are as follows:Firstly, a cylinder-shaped ends of vertical shaft structure was designed,according to the characteristics of the shaft, parts were designed based on structure,material, size and etc of the shaft’s parts were considered. Carrying capacity and filmthickness of restrictor has an important influence on the shaft performance, theFLUENT software was used to simulate the relationship between them, and find themost appropriate supply pressure and film thickness of shaft, and shaft assemblyprocess was researched based on the previous analysis.Secondly, in the case of the newly designed separated aerostatic bearings, spaceforce system was established. The spindle rotation was decomposed into acontinuous balancing process and three-dimensional model of rotational motionerror was built, research was taken on the rotational error affected by geometryerrors and assembly position errors of the shaft, and so as to achieve the purpose ofanalyzing error averaging mechanism. Assume the parallelism error and verticalityerror of spindle were4120.510rad,the flatness error of restrictors was311.5μm,the position errors generated from assembly was412μm,the remainingerrors were negligible. The result show that the error averaging factor was p0.29under the parallelism error while v0.13under the verticality error, rotational errorwasRe11.86μmwhile the parallelism error and the verticality error both exist, androtational error wasRe22.68μmwhile the above errors exist.Thirdly, reverse method was designed to measure shaft rotational error, the experimental principle was analyzed and hardware of experimental apparatus wereselected and designed. Experiment parameters were changed through changingassembly errors. Under the conditions of the three parameters, the relative errorbetween experimentally measured values and theoretical valuewas13%~14%.Considering the complexity of the study and the idealized model, to some extentrotational error model is credible.An exploratory on the separated shaft structure was taken, and the resultprovide some guidance for the future innovative design of separated shaft, theestablished three-dimensional model of rotational error laid the foundation for erroranalysis.