Design And Research On On-line Measuring System Of Conical Screw Thread

The screw thread is a kind of components widely used in the manufacturing. In oil field, the quality of screw threads's connection has great effect on normal oil production. At present, the thread measuring method is still staying in manual method, which has high error possibility and low precision. The other method is mechanical measuring, which has high cost. It is urgent to develop a more effective and low cost screw thread measuring method.To this subject, the theory of a measuring method that combines optical projection with image processing technology is studied in detail. And the factors of this method that may have effect on precision are also analyzed. Then, many image processing algorithms used in the system, especially algorithms in the image denoising, image two-valuing and sub-pixel precise positioning, are deep compared. In the basis of deep study in theory, a system for auto-measuring parameters of external screw based on non-contact measuring and image processing techniques is introduced. Obtains 2-D data of the screw axis profile section by CCD and image gathering card with optical projection and machine driving, and then calculates the needed parameters. The measuring system developed is on the ground of optics, mechanics, electronics and mathematics. In software development, median filter is employed to denoise the screw image, and sub-pixel is applied to process the edge. Least Squares procedure is used to fit the external screw profile line. And then, geometrical parameters of the screw can be calculated. The measuring precision of the system developed is high, and the examining efficiency is greatly improved.