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 tight should the roll pressure be?
Too little pressure lets the wire slip in the rolls, while too much flattens or deforms the wire and causes feeding problems and an unstable arc. Aim for the lowest pressure that feeds the wire reliably.
One common method with a cold torch is to loosen the pressure until the wire slips, then tighten in half-turns until it feeds without slipping, either checking against a wooden block or by holding the wire with a gloved hand. Follow the maker's instructions for your feeder, and wear gloves as the wire can be hot.
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.