Cameras for Monitoring MIG Root and Sub Arc Fill Welds

Manufacturers of steel vessels and structures who are concerned with both productivity and quality often weld the root with open-arc MIG (GMAW) on one end of a column and boom and a sub arc (SAW) process at the other end. The combination of MIG and SAW welding processes is often the most appropriate for butt joints in large steel structures, as long as the joint can be kept in the down hand position.

Root welds typically require tight tolerances; any surface breaking defects are problematic for fatigue, corrosion or other failure modes.

See table below for accessories shown in the image

The MIG process in this application utilizes advanced pulsed waveforms such as CMT from Fronius, RMDTM from Miller or STT®from Lincoln to bridge what is typically an open but may also be a closed root; the root gap typically has some variation due to forming and joint preparation processes. Using pulsed GMAW avoids the need for a backing plate in the sub arc process that was common before these specialized MIG processes were developed. Furthermore, despite welding over tacks, the surface finish with these processes may be sufficient that little or no finishing processes are required.

Following the root weld, the column and boom is rotated to remove the MIG processing end and bring in the sub arc end. The higher amp SAW process is then used to deposit metal and fill the joint in a high quality and highly productive manner.


Due to the size of the structures, a column and boom system with rotators is often used. The welding process may be high off the ground and sometimes inside a vessel. Either way the operator is located at a machine control station and needs to see what is going on to control the processing.  Despite advanced welding processes for the root pass, it must be carefully set up and monitored for this approach to be successful.

MeltView Solution

The most practical monitoring solution is a dual camera system with desigated MIG and sub arc cameras. Our DART2 camera is a direct display camera system designed for monitoring MIG welding. This camera has features designed for quick setup such as external focus and joystick control. Once set up, the camera automatically adjusts between welding and non-welding with no intervention. Crosshairs are integrated in the system and adjusted via the camera controller. If desired, structured light or a pointing laser can be superimposed in the image to provide guidance.

The DART2 camera features integrated lights, an air purge system, cooling channels, and a quick-change spatter shield. The system is protected against shorts and electrical noise and displays 1920x1080 video to an HD-SDI or HDMI monitor. The PIXI camera is set up for monitoring SAW with a high quality, wide angle 1920x1080p image with a large depth of field that doesn’t require refocusing. The camera has many of the features of the DART2 but is optimized for SAW, TIG and Laser processes.

Photo credit: Weld Plus

For monitoring SAW, if it is deployed with a joint tracking system, the camera may be mounted to the side to oversee the whole process including flux delivery and collection. If used with laser pointers for guidance, the camera is typically mounted in the leading position.

For combination MIG root and sub arc machines, the user may select a dual camera advanced controller customized for the two camera systems and an optional laser system, OR two compact controllers for two stand-alone camera systems. In either case the operator may be presented with one or two monitors. If a single monitor is desired, the operator can simply switch channels to the process at hand.

Benefits to customer

  • Simple direct-to-monitor cameras

  • High resolution, high image quality

  • Designed for welding environment

              Product    Qty
  1   MeltView PIXI camera      1
  2   MeltView DART2 camera      1
  3   Advanced controller for laser diodes      1
  4   Flex camera cable      2
  5   Fix arm mount      1
  6   Free arm camera mount      1
  7   Laser diode spot assembly      2
  8   Laser diode power cable      1
  9   15" HD-SDI Monitor 1920x1080      1




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