25 September 2007

High Performance Weld Viewing Systems from Oxford Lasers

The problem with trying to look at welding processes is that the arc produces such extreme brightness and glare that the resulting ‘white out' obscures any view and makes it almost impossible to study such events as the flow of molten metal during welding, the failure mechanism in a jet engine explosion, the interaction of arc, electrode and workpiece, or the malfunction of an arcing circuit breaker.

Oxford Lasers has developed a new, simple and cost effective imaging system for looking deep into the heart of a welding process and for the first time allows engineers to ‘see' through the fireball. Proprietary diode laser technology combined with state of the art cameras has resulted in VisiWeld – imaging systems of unprecedented capability. VisiWeld can see and record close-up images of the weld process where the field of view can be as small as 10mm x 10mm, it can capture transient effects or events that may last as little as 1ms, it allows users to work in complete safety by watching a monitor screen instead of trying to look directly into the fireball, and it is so compact that the air cooled system can be used in the field as well as in the laboratory.

Weld fireballs generally saturate part of any captured image leaving other parts in darkness. Even if very powerful extra lighting is used, it is very difficult to see anything other than the fireball itself. VisiWeld systems combine two techniques to eliminate light from the arc and capture images with amazing clarity.

First the fireball is illuminated using a laser and the camera is fitted with a filter that only allows laser light to penetrate. This means that most of the light from the fireball or weld process (which emits a broad range of wavelengths) is blocked and can be reduced by a factor or 100 or more.

Secondly the lasers can be configured to deliver short pulses of light, while the fireball emits light continuously. If the camera is fitted with a very fast shutter that is only open during the laser pulse, the light from the fireball can again be minimised without reducing the amount of laser light. This can reduce the light from the fireball by a further factor of 100 or more.

Combining these two techniques can reduce the effective brightness of the fireball by a factor of over 10,000 so that welding processes can be imaged with extreme clarity and without motion blur. These images can then be studied while the weld process is going on or stored and used for detailed study and research later.

VisiWeld advanced weld viewing systems use integrated lasers for illumination and are available for general purpose weld viewing with good quality images at standard frame rates, or for time resolved studies and research a high performance system is available using a 5 kHz pulsed laser and high frame rate camera. Optional accessories are offered to expand the range of information that can be gathered, such as data logger system; extended working distance lenses; particle size and velocity measurement software; flow field velocity measurement software and /or hardware; and high magnification /short working distance lenses.

Being able to look at arc welding or brazing operations can help engineers to understand metal transfer processes. VisiWeld means that they can view the welding process with amazing clarity and can see details such as spattering droplets in flight within the arc region, or melt pool dynamics.

Process development involving changes to the parameters of a welding operation has also proved to be a problem for welding engineers since it has been impossible to see what difference any changes might have made until after the process was complete. Now VisiWeld makes it possible to monitor the weld process and check for any change within the fireball area as it is happening. This time resolved facility could even allow adjustments to be carried out during the welding operation. Oxford Lasers has had 30 years of experience in the manufacture and integration of lasers and laser systems worldwide. Their team of highly qualified and experienced engineers is available to advise on the best weld viewing system for any particular situation.

Contact: Seamus Murphy

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