Measuring Diameter of Non-threaded Hex Bolts Based on Hough Transform

Non-threaded bolts are the important semi-manufactures during manufacturing hexagon-head bolts. This paper proposes a vision measurement method to measure the diameter of non-threaded bolt. On the basis of briefly introducing manufacture process, the importance of measuring non-threaded bolts is pointed out. The principle of circle detection based on hough transform is analyzed. Image acquisition software is developed. Median filter is designed to enhance the acquired image. A Canny detector is employed to extract the edges of hexagon-head bolt. Hough transform is used to locate circle in the original image. According to the number of pixels and the dimension of pixel, the diameter of bolt is computed. The experiment measurement system is constructed to illustrate the performance of the proposed method. The result shows that the presented method is effective and the inspection accuracy satisfies real manufacture.