Research On Several Key Techniques In CNC Cutting For Irregular Graph

In CNC cutting industry, there is a kind of need: how to cut the parts if there are not theparts graphs but only the parts’ images. This paper makes research on several key techniquesin the CNC cutting program aiming at two-dimensional sheet metal mainly for irregulargraphics combining image processing techniques and CNC techniques. These key techniquesare digital image contour extraction technique, contour curve fitting compressing techniqueand CNC cutting paths planning technique.Digital Image Contour Extraction technique is related to many techniques. First, imagepre-processing techniques such as gray-scale image processing, illumination compensationand image smooth are necessary. Then this paper proposes the canny image contour extractionalgorithm and eight directions contour tracking algorithm based on OpenCV, and translatesthe contour information to the DXF format. In order to solve the jagged appearance in thecontours, this paper presents a2-envelope average smooth technique.This paper proposes a the hybrid application algorithm of biarc fitting and line fitting tosolve the mentioned problem. After getting the discrete points of the contours to be processed,“Point wise trial and backtracking method” is presented to make more points to be fitted inthe premise of meeting the accuracy and the smooth of contour. For remaining the inflectionpoint of the contour,“inflection point recognize method” was proposed to find the inflectionpoint out, then its tangential is processed again. Finally, a specific irregular shape that is textis used to test the algorithm. The results showIn this paper, there are two steps to solve CNC cutting paths problem. First, determine thecutting sequence and then determine the piercing point of the contour. When determining thecutting sequence, this paper presents two local search heuristics which are “n” shapedalgorithm and “N” shaped algorithm. These two algorithm is according to the parts’ size andrelative position between parts. When determining the piercing point, this paper presents twosteps to solve the problem. First, figuring out the point which is the nearest point in a contourto the last piercing point. Secondly, adjusting the piercing points to make the air travel shorter.