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Drive and feed rolls for wire feeders: how to choose the right groove and size, set the tension and know when to change them.
Feed rolls grip the welding wire and push it from the spool through the liner and torch to the contact tip. The rolls are driven by the feeder motor, and a spring-loaded pressure arm holds the wire against them so there is enough grip to move it at an even speed.Because they are in constant contact with the wire, they have a big effect on how smoothly it feeds. The wrong groove, the wrong size or a worn roll shows up as erratic feeding, an unstable arc, burnback or wire tangling at the feeder, so they are one of the first things to check when feeding goes wrong.
The groove shape suits the wire. V-groove rolls have a smooth V and are normally used for solid steel and stainless wire. U-groove rolls have a rounded groove and are meant for aluminium and other very soft wires, where the aim is not to flatten or mark the wire. Knurled (toothed) V-groove rolls grip the softer outer sheath of flux-cored and metal-cored wire.Using the wrong type causes trouble: knurled rolls can shave solid wire and leave debris, and smooth V-groove rolls can slip on cored wire or crush it if pushed too hard.
The groove size must match the wire diameter. A roll that is too large or too small for the wire causes slipping, poor grip or damage to the wire and leads to feeding problems. Many rolls are marked with the wire size they suit, and some have two grooves for two different wire diameters, so make sure the correct groove is on the wire side.When you change wire diameter, check the roll, the inlet and outlet guides, the liner and the contact tip as well, as they all need to suit the new wire. Check the feeder's manual or roll markings if you are not sure.
Rolls are made for specific feeders, so start with the make and model of the feeder or the machine and check its manual or data plate. Rolls are identified by outside diameter, bore and width, as well as by groove type and wire size, so compare these with your old roll if you can.Also check how many rolls the feeder uses. Two-roll and four-roll feeders take different roll sets, and in some feeders only some of the rolls are driven. Where a kit is sold as a set, fit the whole set as the maker intends. Our team can help you identify the right roll from the feeder details.
A 2-roll feeder has one drive roll and one pressure roll, while a 4-roll feeder has two pairs. Makers of 4-roll feeders describe better grip and smoother wire guidance, which can help with long torch leads, soft wires such as aluminium and cored wire, because the push is shared over more contact points.2-roll feeders are simpler, have fewer parts to replace and are usually perfectly adequate for solid steel wire on shorter leads. Which suits you depends on the wire, the lead length and the duty. A feeder cannot normally be switched from one to the other unless the maker supplies a conversion kit.
Use only enough tension to feed the wire without slipping. A common method is to release the tension completely, then feed wire against a block of wood and tighten until the wire stops slipping, then add about half a turn more. The tension should be set again each time the rolls are changed, and the maker's recommended setting should be used if one is given.Too much tension can deform the wire, cause arc instability or burnback, shave debris into the liner and wear the rolls, while too little makes the rolls slip. Do not use extra tension to cover for worn rolls or a blocked liner.