Aluminum Workshop: The push-pull gun and its perks for GMAW

Q: I will be getting into aluminum welding much more than I have in the past. I want to buy a new set of equipment for gas metal arc welding (GMAW) and I’ve already picked out the power supply and feeder. Should I buy a push-pull gun or stick with the simpler and less expensive push-only gun?

A: In general, I would recommend a push-pull gun, but for some applications a push gun works fine. For instance, if you are feeding either 1/16-in.-dia. 4043 or 5356 and the gun length is 12 ft. or less, a push gun should work fine. Of course, you will still need to be sure you have the correct U-groove drive rolls, contact tips, and guide bushings for aluminum, as well as the correct plastic liner to feed aluminum. Also, you should be sure that your gooseneck push torch doesn’t have a tight-radius or a sharp bend at the gooseneck.

For all other applications, a push-pull torch works best. While you can certainly use a push-pull gun to feed 1/16-in. wire, it really shines when feeding either 0.035-in. or 0.0475-in. wire.

Why?

Wire Feeding in Push-Pull Guns

The column strength of aluminum wire is much lower than that of steel wire. Steel wire has enough column strength that it can be pushed through the gun liner by one set of drive rolls at the feeder. However, if you try to do this with aluminum wire, any restriction in the gun liner or contact tip can cause the wire to buckle in the gun liner, which will make subsequent feeding erratic at best.

The push-pull gun was invented some years ago to prevent erratic feeding from occurring. This gun type is available from many manufacturers in both gooseneck and pistol grip styles. Whichever one you pick, the push-pull gun will incorporate a drive motor within it. The purpose of the motor is to run slightly faster than the push motor at the feeder, always keeping tension on the wire to prevent it from buckling in the gun liner.

Each push-pull gun manufacturer has its own way of adjusting the wire feed speed (WFS) of the front (pull) drive rolls with respect to that of the rear (push) drive rolls. There isn’t room in this column to go through the methodologies in detail. Suffice it to say that, at least in my experience, they all work.

My advice is that if you are having difficulty feeding aluminum wire for GMAW, try a push-pull gun. I think you’ll like it.