Few things are more frustrating than pulling the trigger on your MIG torch and finding the welding wire has melted back into the contact tip.

Known as burn back, this common MIG welding fault can cause poor arc starts, damaged consumables and unnecessary downtime.

The good news is that burn back is usually easy to diagnose and prevent once you understand the causes.

In this guide, we’ll explain what burn back is, what causes it and how to stop it from happening.

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What Is MIG Wire Burn Back?

Burn back occurs when the welding wire melts faster than it is being fed through the contact tip.

Instead of maintaining the correct arc length, the arc travels back towards the tip and fuses the wire inside the contact tip bore.

Common symptoms include:

• Wire stuck inside the contact tip
• Poor arc starts
• Popping and sputtering
• Wire fused to the tip
• Contact tips requiring frequent replacement

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How Burn Back Happens

A MIG welder relies on a balance between:

• Voltage
• Wire feed speed
• Stick-out
• Contact tip condition

When this balance is lost, the wire may not feed quickly enough to maintain the arc.

The result is the wire melting back into the contact tip.

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1. Wire Feed Speed Too Low

This is the most common cause of burn back.

If the wire feed speed is set too low for the selected voltage, the wire cannot replenish itself quickly enough.

Symptoms

• Aggressive arc sound
• Frequent wire sticking
• Contact tip damage

Solution

Increase wire feed speed until the arc becomes smooth and stable.

A properly adjusted MIG welder should produce a consistent buzzing sound rather than a harsh crackling arc.

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2. Worn Contact Tips

Contact tips wear over time.

As the bore enlarges:

• Current transfer becomes inconsistent
• Arc stability suffers
• Burn back becomes more likely

Signs of a Worn Tip

• Oval bore
• Excessive spatter
• Wire wandering in the tip
• Intermittent arc

Solution

Replace contact tips regularly as part of routine torch maintenance.

Contact tips are inexpensive and should be considered a consumable item.

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3. Poor Wire Feeding

If the wire feed system cannot push wire smoothly through the torch, burn back can occur.

Potential causes include:

• Worn liner
• Dirty liner
• Incorrect liner size
• Damaged wire
• Rusty wire
• Excessive friction

Solution

Inspect:

• Liner condition
• Wire spool condition
• Drive rollers
• Torch cable routing

Replace worn liners when required.

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4. Incorrect Drive Roller Tension

Many operators automatically tighten drive rollers when feed issues occur.

Too much tension can:

• Flatten the wire
• Create drag in the liner
• Cause inconsistent feeding

Too little tension can:

• Allow wire slipping
• Reduce feed consistency

Solution

Adjust roller pressure so the wire feeds consistently without excessive compression.

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5. Bird Nesting at the Wire Feed Unit

Bird nesting occurs when wire bunches up behind the drive rollers.

When this happens, wire feed to the torch becomes inconsistent.

The arc continues burning while wire delivery slows or stops, resulting in burn back.

Common Causes

• Incorrect roller pressure
• Blocked liner
• Worn contact tip
• Poor quality wire

Solution

Fix the underlying feeding issue before replacing consumables.

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6. Excessive Torch Cable Bends

A sharply bent torch cable increases friction within the liner.

This restricts wire feeding and can contribute to burn back.

Solution

Keep the torch lead as straight as possible during welding.

Avoid wrapping cables tightly around machines when stored.

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7. Incorrect Contact Tip Size

The contact tip must match the wire diameter being used.

Examples:

• 0.6mm wire → 0.6mm tip
• 0.8mm wire → 0.8mm tip
• 1.0mm wire → 1.0mm tip
• 1.2mm wire → 1.2mm tip

Using the wrong tip size can affect current transfer and feeding performance.

Solution

Always match the tip size to the wire size.

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8. Dirty or Corroded Wire

Contaminated wire creates additional resistance as it passes through the liner and contact tip.

Bird nesting present. Drive system problem

Common contamination includes:

• Rust
• Dirt
• Moisture
• Grinding dust

Solution

Store wire correctly and keep it protected from workshop contamination.

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9. Incorrect Stick-Out

Stick-out is the distance between the contact tip and the workpiece.

Excessively short stick-out can increase heat concentration and encourage burn back.

Typical Stick-Out

• Short circuit MIG: 10-15mm
• Spray transfer MIG: 15-20mm

Solution

Maintain a consistent stick-out throughout the weld.

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10. Burn Back Control Settings

Many modern synergic MIG welders include a burn back adjustment.

This feature controls how long the wire remains energised after releasing the trigger.

Too Much Burn Back

• Wire melts back excessively
• Contact tip damage

Too Little Burn Back

• Wire left protruding excessively

Solution

Follow the manufacturer’s recommended settings and fine tune if required.

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How to Prevent Burn Back

A few simple maintenance habits can eliminate most burn back issues.

Daily Checks

✔ Inspect contact tips

✔ Check wire condition

✔ Verify wire feed settings

✔ Keep the torch cable straight

✔ Remove excessive spatter

Weekly Checks

✔ Inspect drive rollers

✔ Check liner condition

✔ Clean wire feed system

✔ Check torch connections

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Quick Burn Back Troubleshooting Guide

Problem Likely Cause

Wire fused into tip. Wire feed too slow

Frequent contact tip failure Worn tip

Inconsistent wire feed. Blocked liner

Arc starts poorly. Feeding issue

Wire stubbing into weld. Incorrect settings

When Should You Replace Components?

Contact Tip

Replace when:

• Bore becomes oversized
• Arc becomes unstable
• Wire frequently sticks

Liner

Replace when:

• Feeding becomes inconsistent
• Wire drag increases
• Damage is visible

Drive Rollers

Replace when:

• Roller grooves become worn
• Wire slips despite correct tension

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Final Thoughts

MIG wire burn back is almost always a symptom of an underlying feeding or setup problem.

In most cases the cause can be traced to:

• Low wire feed speed
• Worn contact tips
• Liner problems
• Poor wire feeding
• Incorrect torch setup

Regular maintenance, quality consumables and correctly balanced welding settings will prevent the vast majority of burn back issues and keep your MIG welder performing reliably.

When burn back does occur, focus on diagnosing the root cause rather than simply replacing the contact tip. Doing so will save time, reduce consumable costs and improve weld quality.