Monitoring plasma arc welding

Plasma keyhole welding offers high integrity welds and high productivity, and finds plenty of applications in industries that manufacture products from stainless and titanium (e.g. welding the linear seams of stainless storage tanks). In many of these applications, the torch is positioned such that visual monitoring of the weld process by the operator difficult. A MeltView welding camera used for monitoring plasma arc welding facilitate the operator’s vision, with the direct benefit of lowering the defect count and scrap/repair rate and improved working conditions.

A MeltView welding camera positioned at the front of the seam may be used to monitor the position of the plasma nozzle relative to the weld seam and check the melting behavior as the metal flows around the front of the keyhole to the back. Full penetration plasma keyhole welds have inherent undercut due to any joint gap and material sag at the keyhole root. However, its quite difficult to get the balance right in a keyhole pass so typically a second pass known as a capping pass is used to add material to the top surface, reinforce the weld and eliminate undercut. In the capping pass the plasma torch is modified for a conduction mode type puddle or a second TIG torch is employed to melt filler wire into the conduction mode puddle. A MeltView welding camera is also useful in these applications for checking the wirefeed position and melting behaviour.

In some applications, a MeltView camera is located at the rear to visualize the solidification of the keyhole pass and capping pass. In rare applications (e.g. tube mills where the material moves instead of the welding torch) a camera can be located with a view of the penetrating arc at the bottom surface. If the view permits, the user may monitor the size and position of the penetrating arc with machine vision techniques thereby creating a penetration sensor for the plasma keyhole welding process.

The MeltView MIRA provides a quality image of the brightest arc process – plasma keyhole welding, most commonly used in the manufacture of tube and pipe as well as tanks used for containment and transportation.

MeltTools offers also offers a second generation MeltView MIRA2 camera system with additional features such as image recording, guide lines, and image optimization

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