The Modeling And Analysis Of Spindle System Rotating Precision

Spindle system is one of the most important parts in NC machine tools and precision instruments. The rotating precision of spindle system determines the property and the value of the machines. With the development of ultra-precision machining and test-control technology, higher rotating precision of spindle system is desired, modeling and analyzing the rotating precision of spindle system is a key step in the stage of precision design, and it is essential to improve the measurement precision of spindle system.In this paper, taking the structure of spindle system as an object, the modeling method for geometric precision of parts based on vectors was proposed, and geometric error mapping FEA model of static coupling structure and bear ing-spindle system rotating precision model were built. In the end, taking the structure of photoelectric encoder spindle system as an example, vector representation model for rotating precision of spindle system was established and analysis on the model were done.(1) The characteristic vectors in the geometric precision model were defined. Then, the vector formalism and tolerance constraint inequalities of shape, orientation and location tolerance for plane and cylindrical surface were built. In addition, the transformation of coordinates for precision model was introduced and the geometric precision model of shaft and sleeve in the spindle system was built.(2) The static coupling structure of the spindle system was analyzed and the vector equations were built to describe the geometric shape of cylinder surface and ring plane. The FEA model of static coupling structure was established and nodes-migration method was adapted to simulate geometric error of parts’surfaces. Then the geometric error mapping in the fitting coupling structure between shaft and bearing inner ring was studied. The geometric shape of deep groove ball bearing raceway was expressed by the center and curvature radius of the raceway axial cross section profile which was fitted by least-squares method and the evaluation method for the raceway shape error was proposed. The effect of different bearing assembly parameters on bearing raceway mapping error was analyzed.(3) Taking deep groove ball bearing as the object, the factors which would influence bearing rotating precision were analyzed and the geometric relationships for the rotating motion of bearing were introduced. The analysis model of bearing rotating precision was built, which was based on the contact status between rolling balls with interior and exterior ring raceways of deep groove ball bearing, considering the geometric error of bearing parts. The effects of different factors on rotating precision of bearing were also studied and the coordinate transformation which describes the rotating precision of spindle system was built.(4) The photoelectric encoder and its principle were briefly introduced. Rotating precision vector representation model of photoelectric encoder was built, and the spindle system precision was analyzed by Monte-Carlo simulation method while influence coefficient which means the effects of geometric error on spindle system rotating precision was introduced.