Development Of Fastener Thread Composite Measurement System Based On Electronic Image Measurement Technology

China is the big country of fastener produce and export. Fastener is widely used in industrial field as its standardization. Thread is the core of interchangeability about standard fasteners. It seem to be simple but the pitch angle and the interference by multi parameter lead to test and quality control extraordinary subtle. So far, there is no convenient and economical test method or apparatus for thread measurement,:so that the thread manufacture and quality control has been the main difficulty in fastener field and one of the main sources of defective, claim and safety accidents. The development of a simple and economical thread test and analysis technique is significant.This project developed a simple and reliable fastener thread composite measurement system with electronic image measurement and computer image processing technology. Through manners of threshold graph analysis and illumination test to compare influence factors, designed an optical system, gets the image with narrow boundary gray area and clear contrast between solid and background. Through thread structure analysis to deduction the mathematical model of3D reduction from2D image, solved the physical defect of using2D projection technology in thread measurement. Use image filtering, edge detection operator, edge fitting and parameter identification algorithm to achieve accurate processing. Created the self-calibration method by major diameter solved the declination been verified from traditional calibration used in image measurement. Utilize actual measurement comparison and uncertainty evaluation method on testing and calibration to get an objective assessment of this system that it is meet the measurement requirement. Demonstrated the feasibility of thread quality control by image method adopt subsequent application practice and quality analysis. Effectively improved the level of quality control of factory, and figured out the practical problems in public technology service by testing laboratory. The final completion of the thread composite measurement achieve the purpose of rapid thread quantitative analysis and guide screw optimization in production.