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Straight answers to the questions people ask when choosing, setting up and replacing individual wire feed rolls.
Feed rolls grip the welding wire and push it from the spool, through the feeder and down the torch cable to the contact tip. The wire is pushed by a driven roll working against a pressure roll, and the groove in the roll is what holds the wire.Because they feed the wire the whole time you weld, the grooves wear and the wrong roll type or size causes slipping, a flattened wire and an unstable arc. Choosing the right roll matters as much as choosing the wire.
It depends on the wire. V-groove rolls suit solid steel and stainless wire. Knurled V-groove rolls, which have small teeth to grip, suit flux-cored and metal-cored wires. Smooth U-groove rolls suit aluminium and other very soft wires. A U-cogged type exists for very soft cored wires.The wrong type either slips or bites into the wire. Check the wire maker's recommendation and your machine manual before ordering.
The groove must match the wire diameter. A roll made for thicker wire will not grip a thinner wire and the wire will slip, while a roll that is too small can crush it. For example, a 0.9 mm wire needs a roll marked for 0.9 mm.Check the size on the roll, the wire spool and your machine manual. If you are replacing a roll, read the size stamped on the old one, or the machine manual, and match the roll type to your wire as well.
Some rolls have a groove on each face for two different wire sizes, for example one for 0.8 mm and one for 1.0 mm. The groove on the side facing the wire is the one in use, so the roll must be fitted with the correct size outward.Fitting it the wrong way round can over-grip the wire and deform it, or cause slipping. Check the markings on the roll and the machine manual each time you change wire size.
Use the machine maker's recommended setting for your wire type if there is one. Otherwise, back the tension off until the wire slips when you pull the trigger, then tighten gradually until it just feeds without slipping. Too little pressure makes the wire slip, while too much flattens or deforms it, causes feeding problems and an unstable arc.Different wires need different pressures, and soft or cored wires usually need less, so re-check when you change wire.
Worn grooves lose their shape and slip, even when the pressure seems right. Signs include uneven or hesitant feeding, wire slipping, bird-nesting and a build-up of metal shavings in the groove. People often raise the pressure to compensate, which then flattens the wire and clogs the liner.Before replacing the rolls, clean them and check the liner, guide tubes and contact tip, because these cause similar faults. Replacing worn rolls as a matched set is good practice.