Design and Development of Quality Inspection System for Forming the Longitudinal-Seam Submerged Arc Pipes with JCOE Process

In the line-pipe industries with JCOE process, the unbend angle after removing punch load varies from the target angle due to elastic recovery in each bending step for forming the longitudinal-seam submerged arc pipes. This variation causes bad roundness in formed pipe and inconvenience of performing subsequent welding process. To improve the roundness, the unbend angle should be measured precisely and the compensation for the variation should be conducted in next bending step. The quality inspection system designed to real-time measure the unbend angle was developed based on machine vision technique in this investigation. The system structure, the mathematical model converting the angle identified in the image into actual angle in the world frame, and the line detection algorithms are illustrated in detail. A prototype was designed and developed to test the performance of line detection algorithms. Experimental results have indicated that the accuracy for identifying the unbend angle reaches 0.5 degree and the mean cost time is less than 150 ms. Inspections performed by the prototype have proved the effectiveness and value of line detection algorithm proposed in this quality inspection system.