PTA is particularly beneficial when dealing with complex geometries where there are a number of changes in thicknesses, or intersecting features.
In PTA, the electrode is non-consumable, and hidden within a nozzle through which argon passes and gets ionised. The PTA process is generally used to deposit most of the weldable alloys, such as alloys of titanium, aluminium, iron, nickel and many more. This process normally operates within an inert environment, which effectively shields the deposited material. Both global and local shielding can be employed for the PTA process.
Additionally, the wire feedstock must be fed from preferential directions, usually from the front or the side of the weld pool. This assigns an operational direction to the deposition head and requires the torch to be reoriented along the deposition path. We manage this automatically within WAAMPlanner.
Crucially, when using the PTA process, both the heat input and the material feed rate can be controlled independently by varying the deposition current and the wire feed speed at the same time. This is key to avoid lack-of-fusion defects and achieve the correct layer height.
RoboWAAM comes with PTA sources provided by EWM.
MIG is suitable for less complex geometries, with few intersecting features or little changes to their thickness.
Different to PTA, in the MIG process the wire is the consumable electrode and is coaxial within the deposition head. The MIG process can use different steel grades but also numerous aluminium alloys and nickel alloys. Both global and local shielding can be employed for MIG processes.
The MIG process is characterised by a relatively higher deposition rate when compared to the PTA process, but it does not offer the possibility to control wire feed speed, travel speed and electric arc parameters (voltage, current) truly independently from each other. This is because there is normally a synergic relationship between wire feed speed, current and voltage to achieve a stable and consistent transfer behaviour of the molten material. With MIG, the reliance on synergic lines also means that whenever you want to deposit a new material, a new synergic line must be developed.
RoboWAAM comes with MIG sources provided by Fronius, and specifically with their Cold Metal Transfer (CMT) variant.
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