Abstract: The volumetric error coupled by geometric errors of parts is the main reason affecting the machining accuracy. How to determine the influence degree on the processing precision generated by the geometric errors of parts, thus distribute the geometric errors of parts economically and reasonably, is currently a difficult problem of machine tool design. Based on the theory of multi-body system and sensitivity analysis, a new method of identifying the key geometric error sources parameters is proposed. Taking a four-axis precision horizontal machining center as example, the precision model of the machine center is built up with the theory of multi-body system, thus a mathematical model for error sensitivity analysis of four-axis computer numerical control machine tools is established with matrix differential method, finally the key geometric error sources which affect the machining precision are identified after sensitivity coefficient of error are calculated and analyzed. Calculation and example show that geometric error factors of major parts that have relatively significant influence on comprehensive spatial error of the machine tools can be identified effectively, thus important theoretical basis is provided for improving precision of machine tools reasonably and economically.

Key words: Geometric error, Multi-body system theory, Precision design, Precision modeling, Sensitivity analysis