Meta Vision designs automated welding package to improve safety and productivity in nuclear industry

The company claims that the VistaWeld package offers full automation for such applications for the first time. Until now they have been carried out by an operator watching a camera image of the seam and using a joystick to position the weld torch manually. This is significantly slower and with up to 50 or more weld passes needed for the root, hot, fill and cap phases, there is risk of human error, with consequent safety and cost implications. Factors that complicate the welding process are a need for the sensor to see from top to bottom of the groove and to illuminate the sides to ensure positional accuracy, even though the walls can be angled at 1° (near vertical). Another typical requirement is to preheat the parts to around 300°C, ensuring that there is sufficient heat to fuse the material but not enough to cause cracking and compromise structural integrity. The VistaWeld DLS seam searching and joint tracking system is typically used for submerged arc welding of butt, V, and U joints. It not only tracks the seam and positions the weld electrode accurately and automatically, but also additionally can record position correction data for each pass to provide certification of the manufacturing process. This is an important feature for the nuclear industry where traceability is mandatory. In fully automatic, multi-pass control mode, during the first pass of each layer, the system measures the joint width at that depth and determines the number of passes required for the layer. During the last pass of each layer, the system measures the remaining depth and determines whether to continue with filling or go to capping. Advanced adaptive fill to compensate for joint area variations by controlling welding parameters directly to adjust the deposition rate at each point on the joint is available as an option. Alternatively, in semi-automatic mode, the operator manually selects the type (root, hot, fill or cap) and position (left, right or centre) of the next pass. The VistaWeld DLS scanning-spot laser sensor has proved to be ideal for this application, says Meta. It uses a 2,048 element, linear CCD and has much of the signal processing integrated inside the sensor head itself. Compressed air cooling is provided to keep the unit within its operating temperature range. Water cooling can also be used in the case of high temperature preheats. Meta's DLS sensor is based on a scanning spot rather than a stripe, solving the two main problems of stripe-based triangulation when dealing with shiny materials like stainless steel. First, it is easy to implement effective automatic gain control to compensate for variations in workpiece reflectivity along the length of the stripe. Second, imaging is via the CCD, which only looks at the region of interest and is not affected by reflections.