Robotic twin wire MIG welding is a process whereby two separate power sources are linked via a high speed local bus communication. The two wires are fed through a single hose bundle and terminate in a fairly large welding torch with two separate tips that are set a distance apart. The first wire is responsible for the penetration and is the limiting factor in what can be achieved in the way of increased welding speed. The second wire follows behind and is responsible for the fill. Twin wire welding can give very high deposition rates compared to single wire MIG of up to 30 kg/hr. A limiting factor is the condition of the parent material and any mill scale, corrosion or contamination will result in reduced welding speeds.
It is a common misunderstanding to assume that twin wire welding is twice as fast as single wire MIG. The actual increase in welding speed is about 30% to 40% compared to a non optimised single wire MIG welding process. Twin wire welding is a highly specialised process, that should only be considered for large open assemblies with long joints, typically found in assemblies for earth moving equipment. It requires an additional level of process expertise from the user and many systems in the field have poor performance because companies have failed to recognise the need for in depth training. In practice it is much easier to handle a process with two single wire robots and often this tends to be more productive. Against this is the higher level of investment required for two robots and sometimes the total number of cells (and floor space) that are required to meet a certain output.