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Wire burnback happens when MIG wire melts back into the contact tip at the end of a weld. Instead of stopping cleanly at the workpiece, the wire fuses to the tip, creating a hard blob that blocks feeding. The usual result is a jam, a bird’s nest at the drive rolls, or a contact tip that must be replaced.
Burnback is preventable. The key is to match the welder’s burnback setting and welding technique to the wire size, material, and wire-feed speed. Poor grounding, an incorrect tip, worn liner, and an overly long arc can also contribute.
What Causes Wire Burnback?
The most common cause is stopping the wire feed too early while welding current continues briefly. The wire is still close to the contact tip when the arc ends, so the remaining wire melts upward and sticks inside the tip. This is especially common with short-circuit MIG welding at low wire-feed speeds.
Other common causes include:
- Burnback time set too high: The welder keeps power applied after wire feeding stops for too long.
- Wire-feed speed set too low: The arc consumes wire faster than the feeder supplies it.
- Incorrect contact-tip size: A tip that is too loose can cause unstable arcing; a tip that is too tight can drag the wire and interrupt feeding.
- Dirty or worn liner: Rust, dust, or shavings create inconsistent wire movement.
- Excessive stickout: A long distance from the contact tip to the work reduces current and can make the arc unstable.
- Poor work connection: A loose or contaminated ground clamp causes arc fluctuations and intermittent starts and stops.
- Incorrect polarity: Solid MIG wire normally uses electrode-positive polarity, while self-shielded flux-core wire commonly uses electrode-negative polarity. Always verify the wire manufacturer’s instructions.
Set the Burnback Control Correctly
If your MIG welder has a burnback knob or menu, start near its lowest setting. Many machines adjust burnback in tenths of a second or use an unmarked low-to-high scale. A practical starting range is about 0.02 to 0.08 seconds. Thin wire and low wire-feed speeds usually need less burnback; larger wire and faster welding may need slightly more.
Make a short test weld, release the trigger, and inspect the wire. The ideal result is a wire end that stops about 1/4 inch from the contact tip, with no ball fused to the tip. If the wire is welded inside the tip, reduce burnback. If the wire sticks out excessively—more than roughly 3/8 inch—add a small amount.
Adjust in small steps. A large burnback increase can fix one wire-feed setting but create problems when you change material thickness or wire diameter. If your machine has a “run-in” or “start” setting, that controls the beginning of the weld, not the end. Do not use it to correct burnback.
| Symptom after releasing the trigger | Likely adjustment | What else to check |
|---|---|---|
| Wire fused into the contact tip | Reduce burnback time | Increase wire-feed speed slightly; inspect liner |
| Long wire stub, arc starts poorly | Increase burnback slightly | Check trigger timing and contact-tip fit |
| Wire feeds in bursts or slips | Do not adjust burnback first | Clean drive rolls, set tension, replace liner |
| Burnback appears only at low settings | Use the lowest stable burnback setting | Check ground clamp and cable connections |
Use Correct Wire Feed and Stickout
Wire-feed speed controls amperage in most constant-voltage MIG welders. If it is too low for the voltage setting, the arc can burn back toward the tip. Start with the chart inside the machine’s door or the wire manufacturer’s settings. Change only one control at a time so you can identify the cause.
For short-circuit MIG with solid wire, keep contact-tip-to-work distance around 3/8 inch, or about 10 mm, unless the machine or wire instructions specify otherwise. A longer stickout preheats more wire before it reaches the arc, reducing amperage and making starts less consistent. Pushing the gun too close can also overheat the tip and allow spatter to bridge the tip to the nozzle.
Use a smooth, steady gun movement. Avoid stopping abruptly while the gun is still close to the work. If your welder has a crater-fill or end-of-weld setting, it may reduce end craters and improve wire stopping, but it is not a substitute for correct burnback adjustment.
Inspect the Contact Tip, Liner, and Drive Rolls
A contact tip is a wear item. Replace it when the hole is visibly enlarged, oval, packed with spatter, or when the wire drags through it. Use the tip size marked for your wire, such as a 0.030-inch tip for 0.030-inch wire. Some tips are intentionally sized slightly differently, so follow the gun manufacturer’s recommendations rather than forcing an oversized tip into service.
Keep the nozzle free of spatter with pliers or a nozzle-cleaning tool, and use anti-spatter spray sparingly. Do not spray it into the contact tip or liner. Heavy contamination can break loose and block the wire path.
Remove the liner if feeding remains erratic. Blow it out with clean, dry compressed air or replace it if it is kinked or contaminated. Keep the gun cable in broad curves; a tight bend adds drag. Set drive-roll pressure only high enough to feed the wire. Excessive pressure can deform the wire, fill the liner with shavings, and make future burnback more likely.
For routine maintenance, keep a selection of MIG contact tips and a matching liner available. Cheap tips are acceptable for occasional hobby work, but poorly fitting tips can cost more in misfeeds than they save. For frequent welding, consistent replacement tips are worth buying.
Check Grounding, Polarity, and Consumables
Clamp the work lead to clean, bare metal. A ground attached over paint, rust, mill scale, or a loose joint can make the arc flicker and stop unpredictably. Clean the workpiece near the weld and inspect the ground cable for heat damage or loose connections.
Match polarity to the wire. Solid ER70S-6 MIG wire with shielding gas normally runs DCEP, meaning the gun is positive. Many self-shielded flux-core wires run DCEN. Wrong polarity can produce excessive spatter, poor penetration, unstable starts, and apparent feeding problems.
Use the correct shielding gas and flow rate for the wire. For solid steel wire, a common starting range is 20 to 25 cubic feet per hour indoors, adjusted for drafts and nozzle size. Excessive flow can create turbulence and draw air into the arc; too little gas causes porosity and instability.
When to Replace or Upgrade the Welder
If burnback continues after cleaning the wire path, fitting a new tip, confirming polarity, and adjusting settings, the machine may have a faulty trigger circuit, contactor, or wire-feed control. Test with a fresh spool and a known-good gun liner before buying parts.
A machine with adjustable burnback, run-in, and crater-fill controls is easier to tune than a basic welder with no end-of-weld adjustment. However, a cheaper machine is fine for occasional repairs if it feeds wire smoothly and lets you use the correct consumables. Spend more on adjustable controls when you weld different wire sizes, change materials often, or need repeatable production results. A replacement MIG liner kit is usually a better first purchase than replacing the entire welder.