Flexible assembly research for cylindrical interference fit with form error in shaft-hole structures

Abstract

The interference fit has been widely used for torque transmission and assembly stability in the modern machinery industry. The form error of cylindrical feature is propagated during the interference fit of shaft-hole assembly, which causes the translation and rotation of following structures. Therefore, the overall precision variation is difficult to be predicted. In this paper, an error computational model of interference fit stage is proposed to represent the form error propagation of cylindrical features in the shaft-hole assembly. The characteristic parameter of form error is obtained by the minimum zone cylinder method and integrated into the small displacement torsor. The deformation behavior of interference fit with form error is described as a weakening propagation of error. An interference fit error propagation coefficient is introduced to quantify the phenomenon of weakening propagation of error, which depends on particular fit conditions such as materials, sizes, and interference range of parts. The error computational model for interference fit with form feature is deduced by using the Jacobian-Torsor theory. The characteristic of deformation flexibility in the interference fit is well considered comparing to the simple rigidity analysis in the traditional Jacobian-Torsor model. An error analysis of a shaft-hole structure deciding the symmetry and sensibility performance in the servo valve is conducted to verify the applicability. The cylindrical feature error and deformation during the interference fit are included. The results show that the new error model may represent characteristics of interference fit error propagation with form feature and has a higher reliability than the traditional error models.