Abstract:

A method calculating the geometric rotation accuracy of a precision spindle is proposed. Both the spindle structure and the manufacturing errors of component parts are involved. Firstly, a directed graph of the spindle is built according to the relation among the parts. Error accumulating path and key tolerances are selected based on the graph. Then, key tolerances are modeled with small displacement torsors and the variation propagation within 4 kinds of typical assembly relation between parts is analyzed with the homogeneous coordinate transformation method. Next, key tolerances along the path are linked to complete the geometric rotation error analysis model of the spindle. On this basis, combining with the Monte Carlo method, the vibration ranges of the rotation errors are obtained by statistical analysis and the tolerances are reached. The contribution degree of every tolerance to geometric rotation accuracy is calculated through sensitivity analysis to improve the tolerance allocation. The result shows that this method can predict the geometric rotation accuracy of a high precision spindle and the contribution rate of each tolerance to it effectively.

Key words: accumulating path, geometric rotation accuracy, key tolerance, variation propagation, directed graph