A novel seam measuring method of complex tight butt joint for laser welding

Seam measuring of complex tight butt joint without misalignment for laser welding is a challenging problem. The allowable seam gap width and misalignment in laser welding process are less than 0.1 mm for thin sheet around 2 mm thickness. Current measuring methods or sensors can not stably and accurately extract 3D seam position and seam gap width, due to narrow seam gap and too little misalignment of the butt joint. Furthermore, almost all sensors can not provide seam surface normal vector directly along with seam position and seam gap width. A novel seam measuring method, integrating the 2D machine vision and 3D structured light vision techniques, is proposed. By projecting a unique pattern of three structured light stripes onto the seam surface, 3D seam position, seam gap width and seam surface normal vector can be accurately acquired from a single image, using the 2D/3D vision information fusion approach. Experimental results demonstrate that the proposed seam measuring method is capable of extracting the integrated seam features of tight butt joint without misalignment stably and accurately.