Traditionally, cameras that have been used to record images of various welding processes are implemented with a free running image trigger. This means that images from the camera are acquired as fast as the camera can send them, and only when the camera can send them. However, with a digital Weld camera, such as the Xiris XVC-1000, images can be acquired from the camera when given the signal to do so via the image trigger. This creates an opportunity to tie the image acquisition to a specific event. A typical example of such an event is during a laser weld cycle where the laser power may take several milliseconds to ramp up to full power or to form a keyhole and then, once at full power, may be pulsed to achieve a particular welding effect.
In any of these situations, it can be interesting to acquire an image at a very specific point in time to see a specific feature. This can be done very precisely with the XVC-1000 using an external trigger signal generated during a specific event, such as the point when laser power peaks during a cycle. When combined with a programmable exposure time, images of very specific events, such as only during laser on during a pulsed laser application, can be acquired.
In other types of welding, such as pulsed GTAW, a trigger could be sent at a particular point for each pulse, which when combined with a programmable delay and programmable exposure time, would allow image acquisition to take place at a very specific point in the weld cycle. The benefit is the ability to view the weld pool consistently during a high or low point in the weld cycle and monitoring how it would grow or shrink over time. Another benefit would be for wire fed welding, where the effect of the weld pulse on the wire position as it enters the weld pool could be monitored.
In GMAW processes, the image trigger could be aligned with a specific voltage or current event during the wire contact/expulsion cycle. By acquiring an image at exactly the same point in the weld power cycle, it is possible to study how droplet formation and transfer rates change over time.
Lastly, for alternating polarity welding applications, an image trigger signal could have great value in assisting the operator in setting up the weld torch and determining the ideal weld parameters for each polarity by triggering only on that portion of cycle when the power conditions are met.
An example of a free-running video versus a triggered video. Note: the triggered image acquisition for this video was done at a slow rate, of about 2 Hz.
Conclusion
The use of a trigger signal can greatly improve the quality of images of most welding processes when using a camera such as the Xiris XVC-1000. By clamping the trigger to a specific power event, images can be acquired at a precise point in the weld cycle, allowing for better set up and diagnostics of the welding process.
For more information on how Xiris Weld Cameras can help monitor your weld processes, visit Xiris.com
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