An improved torque method for preload control in precision assembly of miniature bolt joints

Abstract

In this work, the improved torque method based on a mathematical model is proposed for preload control in the precision assembly of miniature bolt joints. The mathematical model was used for predicting the friction-compensated control torque. The predicted control torque is a function of preload and torque gradient which is determined by the friction of contact surfaces. Thus, the effect of friction on preload error was reduced, and the bolts preload scatter due to frictional variables of the bolts was decreased. Experiments were carried out to verify the proposed method using the bolts with a thread of M1.6, and the results show that the scatters of preload were less than ±13.0% in the elastic range, which is more consistent than the conventional torque method. The preload control error for most bolts was less than 10%. © 2012 Journal of Mechanical Engineering.