Vision-based Characteristic Of Weld Pool And Width Of Welding Line Detecting In Plasma Deposition Direct Manufacturing

Through the matching deposition welding parameter, the control of welding quality is carried out in the technology of Plasma Arc Powder Deposition Welding(PDW). The key of the quality control is the characteristic of welding pool detecting. With the characteristic of welding pool detecting, techniques parameter is regulated accordingly ,so the welding quality is guaranteed, thus the feedback of welding parameter is got.On the basis of the prophase research from our laboratory,after the full study of various welding pool morphology tracking system and the comparison of the advantage and disadvantage of a variety of sensors, a passive visual sensor system which meet the requirement of pool morphology and welding line width detecting in PDW was designed. After experimental analysis, an appropriate external filter was designed, and the approving result was obtained. The effect of shooting parameter to the pool image was analyzed and validate, so the optimized shooting parameter was obtained; By comparing various image processing algorithms and also the nature of welding pool morphology was taken into account, max square difference auto threshold and special contour extraction algorithm to obtain the welding pool image information. Through one ordinary method, the coefficient which contact the width from the image processing and the width from the cooling welding line was got. Width detecting on the front and middle of the welding line was done, so the width information is obtained.To understand the difference of welding line width under different experimental parameter and the accuracy of this system ,in this paper, the corresponding plasma powder deposition experiments under the condition of 40~55A currency and 150~330 mm/min deposition traveling speed were done, which added up to 16 experiments. The width of welding line from the image was calculated and from the practical molding was detected. After comparison and calculation , absolute error and comparative error was calculated, The possible reason for this error was analyzed. And the results showed that: the width data werw closed to each other between from the image and from the cooling welding line, the system meet the requirement of welding line width detecting.