Birdnesting is a commonly experienced problem with flux cored wires. Although often portrayed as a wire problem, birdnesting is most often due to a lack of consistent wire feeding. Attention to a few simple areas will ensure consistent feeding and better welding results, so you can get the high production performance you want from your flux cored wire.  

Probably the biggest contributor to wire feeding and equipment failures is incorrect feed roll pressure adjustment. Excessive pressure “notches” the wire surface to the point that it acts like a file on the contact tip and causes the tip to wear prematurely. To properly “set” the drive roll pressure, begin with the torch as straight as possible and the feed roll pressure adjustment backed off completely. Start increasing the roll pressure until you can form a “spring” of four to eight inches by deflecting the wire off the floor, (the larger the wire diameter, the larger the “spring” diameter). When you can do this without the wire “slipping,” the pressure is adequate.

Feed rolls must be the correct size and type for the electrode diameter. The correct wire diameter is usually stamped on the side of the drive rolls. For FCAW electrodes, knurled drive rolls are typically recommended.

Other common problems include:

Improper Spool/Coil Brake Adjustment – When using spools or coils that are mounted to an adjustable hub, adjust the hub so that the spool or coil “drifts” about one-eighth of a turn after welding is stopped. This allows optimization of the feed roll pressure adjustment.

Worn Wire Guides – Wire guides should be the correct size, not excessively worn, and set correctly. The wire guides should be as close as possible to the drive rolls without contacting them. If the wire guide tubes are excessively worn or “ovalled out,” replace them.

Clogged Torch/Gun Liners – Check first that you are using the correct liner size. If the liner is clogged or kinked, replace it with a new one. If the liner has already been replaced, confirm that the replacement liner has been installed correctly by removing the gas diffuser and observing if the liner extends beyond the torch end. The liner should protrude beyond the end of the goose neck far enough to contact the inside end of the diffuser. When replacing the liner, before trimming the excess, roll the torch into a 12-inch circle and then push the excess liner back into the “goose neck” until it stops. Also be sure to remove any burr caused by trimming the liner that could scratch the wire and create metal fillings in the gas diffuser.

Worn Contact Tip/Nozzle – Again, check that you are using the correct contact tip and nozzle. The correct size will limit the recess inside the nozzle to no more than 3/8”. The nozzle should be no smaller than 1/2” diameter. Once the contact tip is “ovalled” out, it should be replaced, as well as any time the arc begins to start harshly or become erratic. An excessively worn contact tip can be perceived as a feeding issue.