Precision Analysis And Assembly Control For Multi-micro Ring Components

The multiply ring component, which is used to transmit power and signals, is composed of multiple circle parts. It is widely used in mechanical arms,robots, coiling machines,aviation,aerospace, sensors and other fields with rotating parts. However, the traditional manual method is unable to meet the needs of the market to the quality and capacity of the ring due to the manual method’s high intensity of labor demand, low efficiency and poor product consistency as well as the ring’s small size and needs to high assembly precision. In order to solve this problem, this paper introduced the high precision multi-ring automatic assembly system and determined influencing factors of the accuracy of ring components through the analysis of the technological process. Relative researches were conducted to improve product consistency and the fitting precision of ring components.After the assemble process was analyzed, it is found that the influencing factors on the accuracy of ring components mainly included the machining error, the precision of the high precision multi-ring automatic assembly system as well as the assembly principle and method of the ring components,etc. Each factor’s influence law was obtained by analyzing the various factors. Because the interference fit assembly was adopted and the assembly mould was harder than the ring part, single ring part’s assembly process did not affect the other rings’. Therefore,an intuitive understanding of the factors which could influence the quality of ring components would be gained by analyzing influencing factors of a single ring part assembly quality.The ring detection system was set up based on the machine vision theory. An industrial camera was adopted to detect the plane warping value of the ring. Since the ring part produced a mirror image when a silicon wafer was used as the supporting plane,the warp was magnified twice,which was advantageous for the image acquisition and processing. Images were collected from eight angles by rotating the platform and then mosaicked to get the panorama of the ring part. After threshold segmentation and edge fitting processing, the values of the warps in eight angles were obtained. In order to ensure the subsequent assembly accuracy, the maximum value of the eight ones should be less than 2S\im for a qualified ring part. According to the precision requirements of the ring component, the high precision multi-ring automatic assembly system was set up. Hardware design and assembly strategy were conducted to ensure the position accuracy and the perpendicularity error of the ring component. In the Z axis direction, the spiral elevator with grating guaranteed the position accuracy of the ring component. The assembly strategy of two steps was to control the deflection error of the ring component. By analyzing the precision of the automatic assembly system, the error compensation model was established. This paper proposed the error compensation method and utilized the method to compensate the system error in the experiment. Through the interactions between software modules, the ring component was completed automatically.The system software was programmed based on Lab VIEW. The software architecture and related functions were introduced in this paper. The software realized flexible control by calling configuration files, and the different requirements of various ring components could be satisfied by changing the parameters in the files.The ring parts’ assembly experiment was conducted by the system. Experimental results showed that when the assembly force was in the range of 3N to 40 N, the maximiam position error was 26^m and the perpendicularity error was 17 nm. The average assembly time for one ring was 75 s. The assembly system could satisfy the requirements of the ring component assembly.