You're mid-weld, the arc sounds fine, and then the wire stops feeding. You pull the trigger again — nothing. When you check the tip, the wire is fused inside it.
That's burnback.
It wastes contact tips, it wastes wire, and it pulls you out of your rhythm. The good news is burnback is almost always caused by one of a few things you can check and fix yourself.
This article walks through what causes burnback, how to diagnose which cause applies to you, how to clear a burnback safely, and what to check before your next weld so it stops happening.
Quick Answer — What Causes Burnback?
Burnback happens when the wire melts back into the contact tip faster than it feeds forward. The most common causes are:
- Wire feed speed too slow for the voltage
- Contact tip worn or the wrong size
- Gun angle too steep
- Inductance set too low (on machines that have it)
- Gun overheating from exceeding duty cycle
The section below helps you narrow down which one is your problem.
What Is MIG Welding Burnback?
Burnback is what welders call it when the wire melts and fuses inside the contact tip. The wire can't feed past the blockage. The tip is usually damaged and needs to be replaced.
It happens because the wire is melting faster than it's being pushed forward. The molten end creeps back into the tip bore and solidifies there.
Contact tips are inexpensive consumables. Replacing it isn't a big deal. But if burnback keeps happening, you're losing time and money to something that's usually preventable once you know what to look for.
How to Diagnose Your Burnback (Symptom → Cause)
Not all burnback has the same cause. When it happens — and how — gives you a strong clue about what's wrong.
| When Burnback Happens | Most Likely Cause | What to Check First |
|---|---|---|
| At the very start of the weld | Wire speed too low for the voltage setting | Check your machine's recommended wire speed range in the manual. Adjust in small steps while listening to the arc. |
| Mid-weld, after running fine | Contact tip worn or wrong wire size | Remove the tip and inspect the bore. If it's oval, worn, or enlarged, replace it. Confirm the tip size matches your wire diameter. |
| After a long weld or several quick welds | Gun overheating — duty cycle exceeded | Let the gun cool. Check your machine's duty cycle rating (printed on the panel or in the manual). Reduce amperage or pause more between welds. |
| On corners, edges, or out-of-position joints | Gun angle too steep | Shallow the gun angle to reduce the chance of the wire burning back toward the tip. The right angle depends on your joint, wire, and shielding gas. |
| Random, happens intermittently | Inductance too low, liner wear, or cable restriction | If your machine has inductance control, try increasing it in small steps — check your manual for how yours works. Also inspect the liner and gun cable for kinks or wear. |
Take a moment to match your burnback pattern to one of these rows. It will save you from adjusting random settings.
Check the Wire Feed Path Before Changing Settings
Before you start adjusting voltage or wire speed, check how freely the wire is feeding from the spool to the tip. Feed resistance can cause burnback all by itself, even when voltage and wire speed are set correctly.
Here's what to check along the wire path:
Spool drag. The spool should spin freely when the wire pulls on it. If the spool brake is too tight, the wire has to fight to feed. Loosen it just enough that the spool doesn't overrun when you stop feeding.
Drive roll tension. The drive rolls should grip the wire firmly enough to push it through the liner, but not so tight that they crush or flatten the wire. If the wire slips under load, the feed slows and burnback can follow. If the rolls leave deep marks, back off the tension.
Liner condition. The liner guides the wire through the gun cable. Over time, dirt and debris build up inside it. A dirty or worn liner adds friction that slows the wire just enough to cause intermittent burnback. If you've ruled out other causes, cleaning or replacing the liner often solves the problem.
Gun cable routing. The wire travels through the liner inside the gun cable. A sharp bend in the cable restricts how freely the wire can move. Keep the cable as straight as your workspace allows. Avoid looping it tightly or running it under a heavy object.
Contact tip and wire diameter match. A .035 tip used with .030 wire leaves the wire loose inside the bore. The electrical contact becomes inconsistent, the arc wavers, and burnback becomes more likely. Double-check that the tip size matches the wire diameter printed on the spool.
If the wire has to fight to get to the arc, it does not matter if your voltage and wire speed numbers are right on paper. The wire cannot feed fast enough to keep up. Check the feed path first.
Caution: Clear Burnback Safely
If your wire is fused inside the tip right now, here's how to clear it safely.
1. Release the trigger and wait. The contact tip may still be hot. Give it a few seconds to cool.
2. Put on welding gloves. The wire sticking out of the tip may be sharp and hot. Gloves protect your hands.
3. Cut the wire at the tip. Use wire cutters to snip the wire flush with the end of the contact tip.
4. Remove the contact tip. Unscrew it from the gun neck. Use pliers if it's stuck, but be careful not to damage the threads on the neck.
5. Inspect the tip. Look through the bore. If it's blocked or the hole is no longer round, the tip needs to be replaced. A damaged tip will cause arc instability even if you clear the blockage.
6. Clear or replace. If the bore looks clean and round, you can try running a tip cleaner through it. If there's any doubt, install a new tip. Contact tips are cheap compared to the frustration of a second burnback.
7. Feed wire through the new tip. Pull the trigger briefly to run wire through the new tip. Make sure it feeds smoothly before you start welding.
Caution: The contact tip is electrically live whenever the trigger is pressed. Always release the trigger before touching the tip or wire. Wear dry welding gloves.
How to Prevent Burnback (Pre-Weld Checklist)
Once you've cleared the current jam, run through this list before your next weld. It takes about a minute and prevents most burnback:
- Check wire speed and voltage — your manual lists a recommended range for the wire diameter and material you're using. Start there.
- Inspect the contact tip — look through the bore. If it's oval or worn, replace it before starting.
- Confirm tip size matches wire diameter — a .035 tip with .030 wire causes poor contact and can lead to burnback.
- Set your gun angle — use a push angle that suits the joint. Avoid an extreme angle that makes the arc burn back toward the tip.
- Check inductance — if your machine has it and burnback has been a problem, try a slightly higher setting. Each machine labels it differently — your manual is the guide.
- Respect duty cycle — if you've been running long beads, let the gun cool. Overheating softens the tip bore and causes feed problems.
- Make sure the wire spool spins freely — a spool that drags or a kinked liner adds resistance that can slow wire feed and cause burnback.
Common Mistakes That Cause Burnback
These are easy to overlook, especially if you're newer to MIG welding:
Mismatched tip and wire sizes. Running a .035 tip with .030 wire leaves the wire rattling inside the tip. The electrical contact is weak, the arc becomes unstable, and burnback becomes more likely.
Ignoring the liner. A dirty or worn liner adds friction that slows the wire just enough to cause burnback. If you've ruled out other causes, clean or replace the liner.
Bending the gun cable sharply. The wire has to travel through the liner inside the cable. A sharp bend restricts movement and can cause intermittent feeding issues. Keep the cable as straight as practical.
Setting wire speed by ear without verifying. Most experienced welders set wire speed by listening to the arc, and that works well once you know what to listen for. If you're new, start with the manual's recommended range and make small adjustments from there.
When to Check Your Machine Manual
Your welder's manual is the best source for settings guidance. This article gives you a diagnostic system and general direction, but the manual has the final word on:
- Voltage and wire speed ranges for your specific machine and wire diameter
- Inductance settings — different manufacturers use different scales and labels
- Duty cycle ratings — usually printed on the panel and listed in the manual
- Contact tip part numbers for your specific gun
When in doubt, check the manual first.
If Burnback Keeps Coming Back
You have worked through the diagnosis table and the prevention checklist, but burnback still happens. Try these steps:
Replace the contact tip. Even if the tip looks usable, a worn bore can cause trouble. Install a fresh tip with the correct wire diameter and see if the problem stops.
Inspect the liner. Remove the liner from the gun cable and check for debris, kinks, or rust. If it is dirty, clean it with compressed air or replace it. A restricted liner is one of the most overlooked burnback causes.
Check the drive rolls. Make sure the drive roll size matches your wire diameter. Look for flat spots, dirt, or wear. Confirm the tension is firm enough to push the wire without slipping but not so tight that it deforms the wire.
Confirm polarity for your wire type. Different wires call for different polarity. Solid MIG wire with shielding gas typically uses DCEP (electrode positive). Some self-shielded flux-core wires use DCEN (electrode negative). Others may be different. Check the wire spool label, the chart on your welder, or the manufacturer's instructions before changing polarity. Using the wrong polarity can cause feeding problems that lead to burnback.
Check the machine manual one more time. Some welders have machine-specific notes about wire feed speed ranges, inductance behavior, or contact tip recommendations that are easy to miss on a first read.
If the problem still will not go away, the welder may have an electrical or drive-system issue that needs a qualified technician.
FAQ
Can I keep using a contact tip after burnback?
Maybe. If the tip bore is clean and round, you can run a tip cleaner through it and reuse it. If the bore is oval, enlarged, or blocked, replace it. A damaged tip will cause arc instability and could lead to more burnback.
Does burnback damage the welder itself?
Burnback usually only damages the contact tip. In rare cases, if the wire fuses deep inside the gun neck, you may need to disassemble the gun to clear it. The welder itself is fine.
Is burnback more common with flux-core wire?
Flux-core wire can behave differently from solid wire, but the same burnback causes apply. One common issue is polarity. Some self-shielded flux-core wires use DCEN, while many solid MIG wires use DCEP. Other flux-core wires may use different polarity. Always check the wire spool label, the chart on your welder, or the manufacturer's instructions before changing polarity.
Putting It Together
Burnback is frustrating, but it is one of the easiest welding problems to diagnose once you know what to look for.
Start by matching your burnback pattern to the symptom table above. Clear the current jam using the safe step-by-step method. Then check the wire feed path for resistance before you assume the settings are wrong. Run the prevention checklist before your next weld.
If burnback keeps coming back, the section above walks you through the next steps — replace the tip, inspect the liner, check the drive rolls, confirm polarity, and consult your manual.
In many cases, the cause is one of the things covered in this article. Work through them in order, and you will save yourself a stack of contact tips and a lot of downtime.
