Optional extras for a constant voltage MIG power source: remote wire feeders, torches, water coolers and interconnecting cables, and how to match them.
What does a separate wire feeder do with a constant voltage power source?
With a constant voltage (CV) power source you set the voltage on the power source, and the wire feed speed, which largely controls the welding current, is set on the wire feeder. A constant-speed feeder is the usual partner for this type of power source. The feeder also carries the wire spool, drive rolls and torch connection, so it can sit close to the job while the power source stays put.
A voltage-sensing feeder is a different design, so check that any feeder you choose is intended for your power source type and connections.
Should I choose a two-roll or four-roll wire feeder?
Both can feed wire well; the choice depends on the wire and the job. Two rolls suit small, hard steel wires and are also best for soft wires such as aluminium, where heavy drive pressure can crush the wire. Four rolls are better for larger hard and flux-cored wires, long torch cables and wire supplied in large packs, because the first set of rolls helps straighten the wire and the second smooths feeding.
Look at the wire sizes and types you plan to run and the torch cable length before deciding, and check the power source and feeder manuals for what the feeder is designed to take.
How do I choose the right drive rolls for my wire?
Drive rolls must match both the wire diameter and the wire type. As a general guide, smooth V-groove rolls suit solid steel and stainless wire, knurled (sometimes called V-knurled) rolls suit flux-cored wire because the teeth grip the soft tubular wire without heavy pressure, and U-groove rolls suit soft aluminium wire. Names and recommendations vary, so check the wire maker's and feeder maker's recommendations.
A roll of the wrong size or type can slip or deform the wire, and the wrong roll can shave the wire and fill the liner with debris. Inspect the rolls each time you fit a new spool.
How tight should the drive roll tension be?
Only as tight as needed to push the wire through the torch without slipping. Too much pressure can flatten or deform the wire, which can cause feeding problems further along, and if the wire path is restricted it can lead to a bird's nest at the rolls. Cored and aluminium wires are especially easy to deform.
A widely used method is to release the tension, feed wire against a gloved hand or a block of wood, then tighten gradually until the wire stops slipping, adding only a little more. If the maker gives a setting method for your feeder, follow that. Never put your fingers near the rolls while the feeder is live.
What causes bird nesting at the wire feeder?
Bird nesting is a tangle of wire at the drive rolls. It usually happens when the wire is blocked further along and the rolls keep pushing. Common causes are a liner that is cut too short, too tight for the wire, dirty or damaged, a contact tip that is worn, blocked or burnt back, drive rolls of the wrong size or type, and tension set too high.
Check the feeder first, then work towards the torch. Inspect the rolls and guides, then try pulling the wire through the torch by hand with the tension released. Heavy drag points to the liner or tip. Keep the torch cable as straight as practical while welding.
Does a longer interconnecting cable affect the weld?
It can. Longer cables add resistance, which causes voltage drop, so the voltage at the arc may be lower than you set. Signs include a short, tight or stuttering arc, hot cable connections or crimps, and having to keep raising the voltage. Turning the voltage up only hides the cause.
To limit the effect, use leads sized for the current, upsize them on long runs, keep every connection clean and tight, and avoid unnecessary joins. Count the whole circuit, because the work lead is part of it. Keep long cables straight rather than coiled, and use the cable sizing information in the power source manual.