Hey Larry!
Not to disagree with your description, and analogy of why the "dabbing" technique of feeding the filler wire to the molten pool when welding Aluminum or magnesium & both of their respective alloys... Just to add on what you mentioned when you used the analogy of the filler wire having a "Sausage casing" of an Aluminum oxide layer that needs to be blasted off in order to to prevent LOF which is a common RT indication due to the condition left at the unetched piece of filler usually the backside of the filler wire furthest away from the arc plasma's cathodic inonic bombardment...
Another indication that can also be shown as an RT indication is porosity due to the Aluminum oxide containing "moisture" thus resulting in the moisture becoming trapped under the surface of the weld at or near the root of the weld along with LOF indications...:( That's why it's extremely important when welding aluminum using DCEN, that both the filler wire & base metal be cleaned properly, and slightly preheated prior to welding since there's no cathodic bombardment occuring when using only DC straight polarity!
So, not only should the filler wire be clean and wire brushed with stainless steel wool in order to minimize or even eliminate the amount of aluminum oxide on the backside of the filler from being deposited into the weld, welding technique must be taken into consideration also...
Cleanliness should be the Mantra when preparing to weld aluminum!!! The base metal also must be cleaned as should the quality of the shielding gas be checked in order to ensure moisture content is'nt a potential porosity issue as would the possibility of a torch not in optimal working condition, especially a water cooled torch and the condition of the torch parts as well as the tungsten itself!!! Fixturing must also be taken into consideration in order to ensure cleanliness as should the cleanliness of the welding gloves also. :) :) :)
The "Dabber" technique or method is also used when rebuilding knife-edge seals for jet engines, rebuilding surfaces found to worn on steam turbines for power plants. in additon to being used to rebuildjet engine seals, it can be used to provide build-up on jet engine blades, saw blades, valve seats, milling cutters, drill bits, mower blades and other devices... However this method when used to rebuild the surfaces of these devices use an automated version of "dabbing" the wire into the molten weld pool and is a very precise, consistent method of depositing RT quality welds on these surfaces usually consisting of alloys such as titanium, high nickel alloys, and tool steels. CK worldwide also makes a semi-automated version of this equipment so that automated version of this technique can be deposited manually...
In other words, this variation uses a coordinated motion of the cold filler wire end, and the welding torch which varies the arc length... This motion duplicates the motions of a manual welder but is performed automatically... The cold filler wire is fed continuously however, it is fed inot and removed from, the arc by a dabbing or oscillating motion. At the same time, the arc is lengthened and shortened together with the feeding of the cold wire... The dabbing stroke length is sufficient to pull the end of the heated wire from which a droplet has just been detached... At the same time, the torch moves toward the puddle and the arc is shortened... (This part would have to be performed manually with the semi-automated version of this equipment) This simulates the tow handed action of a human welder... It was accomplished by moving the wire guide in and out and the torch up and down... The wire approaches the weld pool at a very shallow angle... This coordinated motion variation can also be used with pulsed current which is what I prefer (I personally used this equipment welding miles of Titanium alloys and of course, they also had trailing shields attached).
If one is GTA welding pipe, then the "dabbing" method or technique should be discouraged to use especially in open root deposits... If extra care is taken in preparation as mentioned above, and pulsed current is used then, one should be able to avoid any of the indications that may show using RT no matter what type of metal is being joined by using the continuous feed into the leading edge or the top of the leading edge of the puddle technique. Otherwise known as the "laywire" technique as Al coined it. :)
Now after the root has been deposited when welding on pipe, one can convert back to the "dabbing" technique if preferred and depending on the metal being welded, it's sometimes advantageous. ;)
So in summary, it comes down to the proper application of these techniques when necessary, the method of NDT required, and the skill level of the welder who should be able to recognize the advantages, and disadvantages of both techniques and how to properly apply then accordingly. :)
Respectfully,
Henry, but you can call me "Hank!" ;)