Abstract: Aiming at the problem of low precision and large error of spring forming machine, the geometric error of spring forming machine was defined, identified, measured, modeled and compensated. According to the spring shape characteristics, the multi-body system of spring forming machine was divided. Based on the theory of multibody system and homogeneous coordinate transformation, a complete model containing twenty geometric errors was established. By using Sobol sensitivity analysis method and Monte Carlo sampling method, the key error was identified as the tool positioning error. On this basis, a micrometer with a magnetic gauge base was used to measure the tool positioning error, and the error compensation benchmark was determined. Finally, the tool axis positioning error was compensated by impulse compensation method based on PMAC system. The results shows that there are 20 geometric errors in the forming process of spring forming machine, in which the influence weight of tool positioning error is 55%. Before error compensation, the positioning error of forming machine is a unilateral error, the size is 0.3 mm. After compensation, the tool positioning error is reduced to about 0.16 mm, and the positioning accuracy is improved by 44.6%. The experiment verifies that this method is suitable for the compensation of geometric error of spring forming machine, and fills the gap in the research method for the forming precision of spring forming machine.

Key words:  spring forming machine; geometric error; sensitivity analysis; error compensation