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Guidance on choosing, setting up and looking after the drive rollers and torch parts used on a MIG wire feed system.
The groove shape has to suit the wire. A smooth V-groove is normally used for hard solid wires such as mild and stainless steel. Flux-cored wire is hollow, so it generally needs a knurled (toothed) V-groove or similar profile that grips without crushing the core. Soft aluminium wire needs a smooth U-groove so the wire is supported rather than squashed.A cogged U-groove is also used for very soft cored wires. If you are unsure, check the wire maker's recommendation and the feeder manual before ordering.
The groove size must match the wire diameter, as well as the wire type. A groove that is too small can shave or damage the wire, and one that is too large can lose grip and let the wire slip. Many rollers have two grooves, one on each face, for two neighbouring wire sizes, and fitting the roller the wrong way round can leave the wrong groove in use.Rollers are normally marked with the groove size, but marking styles vary, so check the roller itself and the feeder manual. Fit the groove that matches the wire in use, and check the guide tubes match the wire size as well.
Flux-cored wire has a hollow tube filled with flux, so it can be flattened or deformed more easily than solid wire. Raising the pressure to cure a feeding problem can push teeth from knurled rollers into the wire, and those marks then wear the liner, guide tubes and contact tip.Rather than adding pressure, check that you have the correct knurled roller for the wire, that the groove size is right, and that the liner and tip are in good condition. Use the lowest pressure that feeds smoothly.
Signs include the wire slipping even when the tension is correct, uneven or jerky feeding, shavings or dust building up around the feeder, and a groove that looks widened, flattened or has lost its sharp teeth (on a knurled roller). Knurled rollers tend to wear faster than smooth ones.It is good practice to look at the rollers each time a new spool is fitted. When a roller is replaced, check the guide tubes and liner too, as a worn guide tube can bring back the same feed resistance.