SAW camera systems

Submerged arc welding yields high quality welds. The SAW process is also highly productive but needs to be mechanized due to the high currents and flux requirements. The flux system necessitates welding in the 1G, 1F or 2F position. Due to typical geometries and welding positions, SAW is often conducted at height (by way of a column and boom) or in otherwise inaccessible situations (e.g. inside of a pipe or tank). Inaccessible applications necessarily benefit from the use of a camera to monitor the process for variations in the groove or delivery of flux.

Our small MeltView® PIXI welding cameras are often used to monitor submerged arc welding SAW as they provide full high-definition, (1920x1080) low latency video with integrated protection and lighting. When set-up for SAW, we typically provide large color field of view encompassing preceding joint, the flux delivery mechanism and any tracking tools. The depth of field is set so that no lens adjustments are required and lighting ensures a crisp and clear image. For applications using lasers for manual control of crosshairs, the torch clamp camera mount is typically selected. For applications with automatic control of the torch position, a camera may be mounted off the machine frame.

See links to our recommended system components at the end of this article.

The machine may be set up to control the position of the torch relative to the seam with an automatic system (e.g., mechanical or optical seam tracking). In this case, a camera is used to adjust allowable parameters or to stop the process if something is not correct. In this scenario, the camera may be offset from the weld joint, and a free-arm camera mount may be suitable.

When SAW is manually controlled, the operator will adjust torch position slides horizontally and vertically. A PIXI camera may be used to monitor the position of lasers projected into the joint in front of the flux. On a video monitor the operator will observe these laser projections and maintain the ideal welding position as well as monitor the observable features such as joint variation and perhaps flux delivery. The projected laser(s) serve as a proxy for the position of the wire in the joint and the torch height above the joint. The position of the laser(s) are maintained within certain tolerances determined by crosshair overlays, as described below.

A laser dot or crosshair helps the operator maintain optimum torch height and the wire in joint center. It may be helpful to think of the laser indication as the point the wire will be a second later. In submerged arc welding, the wire in the groove is hidden by the flux.

The XYZ mounting system allows for great flexibility to move camera and laser stages laterally along the arm as well as rotationally. Two different arm lengths are available, 300mm (12") and 400mm (16"). The mounting system can accept a second laser diode or be used to mount other accessories, such as an optical pyrometer for ensuring correct preheat.

The arm is generally located above and parallel to the weld joint. The primary laser is typically mounted on a stage close to the torch and pointed nearly parallel to the welding torch axis to provide the reference location. The exact position will depend on the flux coverage, camera field of view and allowable variations. The camera is typically mounted on the middle stage and set to view the flux coverage towards the back half of the screen with the weld joint dividing the screen from the front half. The camera is set at a much greater angle to observe the overall process.

With this setup any changes in torch height will be noticed as the laser moving across the screen. The torch height is then adjusted to “zero” or “ideal” welding position, and the laser dot(s) are positioned to be in the center of the joint towards the front half of the screen. A mark may be made on the test piece where the extruded wire (no flux) aligns with the joint. The torch can then be driven off this point to check the alignment of the lasers. Either the mounting arm angular rotation about the torch may be adjusted, or the laser aim on the stage adjusted, and the process repeated until the alignment is correct.

The on-screen crosshair display may now be activated via the camera controller. The vertical lines are set to indicate the acceptable bounds for wire within the groove, i.e. the x or horizontal position. During welding, if the laser exceeds the vertical overlay crosshairs, the operator will move the torch left or right so that the laser is within the marks. The height of the torch above the workpiece may change with material variations from the forming and cutting processes, such as ovality and flatness. Any increases to the torch height will be noticed as the laser moving towards the bottom of the screen and a decrease away from the bottom of the screen.

The horizontal crosshair lines are set above and below the points to indicate the limits of acceptable torch height. If the operator keeps the laser projection within the adequate crosshair bounds, he can be confident that the electrode hidden by the flux is in the correct part of the joint and at the correct torch height. Some users appreciate a secondary laser pointer located on the opposite side of the camera at a larger angle than the camera to emphasize height changes.

• Low cost direct-to-monitor system
• High image quality
• Integrated LEDs for dark locations
• Focusable laser diodes and integrated crosshair overlay for maintaining torch position within groove and height
• Adjustable mounts provide positioning flexibility of laser spot and camera position for different jobs
• Integrated cooling channels and temperature measurement for protecting gear in 'hot' jobs