Research On The Mechanism Model And Structure Processing Of Machine Tool Accuracy

Accuracy-characterization is the important index for performance of machine tool. In the process of design and manufacturing, the research of accuracy is mostly refered to manufacturing and testing. In this research, from the perspective of design, the notion of part, link, pair and whole machine tool error are defined.The accuracy-characterization is enhanced by improving the structure and procecing of machine tool. This work has been deeply researched. And it is supported by the Natural Science Foundation of China under grant NO.51275067, Sic-technical Support Project under grant NO.2011BAF11B03 and the pratical application.First, a geometric accuracy model in theory mechanism is presented. The component and element are simplified to link and kinematic pair. The link error and the kinematic pair error are separated by minimax method from the deviation of linear motion. Then, the closed kinematic chain mechanism error equation is established by elastic motion gemometry, and the accuracy model is deduced by vector method, and a basic evaluation system is esblished for the study of the open kinematic chain mechanism machine tool.Second, an elastic accuracy-characterization mechenism model is set up. The affections of machine tool under assembly factor, elastic factor and thermal factor are analysised. The accuracy-characterization mechenism model in theory mechanism is presented. Under the cold and warm testing, the deformation of machine tool kinematic chain is caculated. The the variationy of accuracy are analysised. The contribution of link error and kinematic pair error are coming into the basic to accuracy improment.Third, the influence of structure to static accuracy-characterization is analyzed. Based on the characteristic of geometric, processing, and constraint load, the cross-section, ribbed slab and ribbed plate of components are analysised. The structure improvement of column, bed and spindle box is accomplished under the map of structure characterization and the accuracy. The accuracy-characterization of improvement kinematic chain is caculated. The variation of accuracy of cold testing and warm testing is constrastive analysised.Fourth, a method called pre-deformation for assembly performance for machine tool is presented.The affection of links process and kinematic paires process is analysed, and the error is compared uner the condition of ideal and realistic following the fixed connection components and elements.This method is technically based on the characteristics and the deformation in multiple conditions.The goals of this method is to improve the static accuracy-characterization, and the the static accuracy-characterization is tested under pre-deformation. The measuring results show that the normal direction straightness of the X axis is 2.4 μm, the Y axis is 2.1 μm. and that of the Z axis is 3.2 μm. This difference is mainly attributed to the installation error. EYZ is 5.2μm, which has been reduced 75.62%. This research proposes a pre-deformation machine center assembly method which has sufficient capacity to improving assembly accuracy of machine centers.