Fronius Feed Rolls FAQs
Straight answers to the questions people ask when choosing, fitting and looking after wire feed rolls for a MIG machine.
Which groove shape do I need: V, U or knurled?
The groove shape is chosen to suit the wire. V-groove rolls are the usual choice for hard solid wires such as mild steel and stainless steel. Knurled V-groove rolls are normally used for flux-cored and metal-cored wire, which has a hard sheath and needs extra grip. U-groove rolls spread the pressure on soft wire such as aluminium so it is not crushed.
Using the wrong shape is a common cause of slipping, deformed wire and poor arc stability, so check the groove against the wire before looking for other faults.
How do I match the roll to my wire diameter?
Each groove is made for a particular wire diameter, so the roll must match the wire you are feeding. A mismatch can cause slipping, an erratic arc or wire that is deformed or shaved on its way through.
The size is normally marked on the roll or listed in the machine's parts list, so check the manual for your feeder. Some rolls have a different groove on each face, so make sure the groove you want is on the outside, facing the wire, when you fit it.
How do I know when feed rolls are worn?
Feed rolls are wear parts and knurled rolls in particular wear out, so inspect them regularly. Worn rolls become less effective at moving the wire, so you may see erratic feeding or slipping even when the pressure is set correctly.
Do not simply tighten the pressure to cover slipping, as this can flatten the wire and wear the liner and tip faster. There is no fixed replacement interval, as it depends on the wire, the amount of welding and the settings.
My wire keeps slipping or birdnesting. Could it be the rolls?
It can be, but check the whole wire path. Look at whether the groove type and size match the wire, whether the rolls are worn and whether the pressure is sensible. Then check the parts after the rolls: a worn or dirty liner, a contact tip that is the wrong size and tight bends in the cable all add load.
A quick check is to see how smoothly the wire pulls through the torch with the pressure released. Heavy drag points to the liner or tip rather than the rolls, and a liner that needs force to pull wire through should be replaced.