Automation, a subset of machine welding, involves a high level of control. The diagram below may help understanding the concepts involved.
In manual welding, placement of the welding torch and control of the welding process lie solely with the welder.
Machine welding is considered to be a generic term used for situations where the welding activity is assisted by a mechanism. In this context, the term 'mechanised welding' is occasionally used, leading to confusion with respect to the definitions set out below.
In situations involving a high level of manual involvement, the term 'mechanised' may be used. In submerged-arc welding, for instance, mechanisms move the welding head relative to the work piece, feed the welding wire and often manage the flux control. The welding operator will control and set the parameters and usually guides the weld head as it is mechanically driven along the joint line.
In this scheme of definitions, 'automatic' welding refers to dedicated machines, whereas 'robotic' welding applies to machines which can be programmed to perform several different tasks (often sequentially in the same cycle). When operated at their basic level, automatic machines or robots have piece-parts delivered to them with a high degree of consistency, especially in terms of dimensional tolerance. The result is that the operator can simply place the parts in the machine, press the start button and welding will be performed.
However, some adaptivity is required when the piece parts vary or when different makes of welding equipment are used. To be adaptive, it is necessary for the system to first sense some measure of the variation that is occurring, so that control can ensure that appropriate corrective action is applied.
In the first instance, it may be necessary to find, or recognise the position of the joint (for welding to start at the correct point, for example). Next, it might be necessary to follow or track the joint. Both of these adaptive functions involve the physical relationship between the weld head and the joint-line.
It might also be necessary to perform weld recognition so that the welding process itself can be adapted to give control, for example, over variations in the joint preparation. One approach taken consists of varying the welding travel speed as the volume of the weld joint changes.
The control systems outlined above operate as welding takes place. In contrast, longer-term control loops look at data after the event and then feed the information acquired back to the beginning of the operation, prior to restarting the process of welding the next unit. For instance, the shape of the weld bead produced can be analysed, and process performance can be assessed. If poor values are found, then adjustments will be made to the welding machine with the aim of improving performance.
Remote viewing systems can also assist operator's control welding processes.
For more information, please contact TWI's manufacturing support group.