Precision assembly method of a kind of small interference fitting parts

Abstract

Interference fitting parts are widely used in many engineering applications. Press-fit method is commonly used for assembling interference fitting parts, but most of press-fit instruments cannot meet assembly requirements of small precision parts for poor accuracies of positioning, alignment and pressing displacement’s measurement. In this paper, the press-fit method of a kind of small precision interference fitting parts was introduced. In order to achieve a reasonable assembly of the interference fitting parts, the influence of aligning error and positioning error on assembly accuracies were analyzed by finite element method (FEM). Furthermore, the relation between pressing force and displacement were also analyzed to obtain a reasonable range of force–displacement curves, which can be used for assembly quality estimation. An automatic press-fit instrument was developed. Through analyzing relation between pressing force and the instrument’s elastic deformation, press-fit displacement error was compensated to increase assembly accuracy. A kind of machine vision device with upper and lower CCDs was used to detect relative situation of parts, and calibration method of the machine vision device was proposed. The assembly experiments showed that press-fit force–displacement curve was consistent with the predicted values. The parts’ relative position deviation was less than ±5 μm, and parallelism deviation was less than 10 μm, which meet the requirements of the assembly accuracy index.