What's inside
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Run-in and burnback controls change what happens at the start and end of a MIG weld. Run-in can reduce the wire-feed speed briefly as you begin, helping avoid a hard wire jab. Burnback keeps the wire energized for a short time after the feeder stops, melting it back so it does not freeze into the weld or stick out too far. Used well, these controls make starts and restarts more consistent. Used poorly, they can cause inconsistent starts, a stuck contact tip, or a wire end that is too short to restart easily.
What the controls do
On most MIG machines, run-in affects wire speed at the start of a weld. The machine may feed wire more slowly until the arc establishes, then switch to the main wire-speed setting. Some welders instead offer a fixed run-in speed; others use a percentage or a short timed ramp. Check the manual, because a dial marked “run-in” does not work identically on every machine.
Burnback acts at the other end. When you release the trigger, the wire feeder stops, but the arc stays on briefly. That delay melts the wire back from the puddle. Too little burnback can leave wire fused to the work. Too much can melt the wire back into the contact tip, where it may jam or damage the tip.
These are separate from preflow and postflow. Preflow releases shielding gas before welding; postflow continues it afterward. Run-in and burnback concern wire and arc timing, not gas coverage.
When to adjust them
Adjust these controls if you have a repeatable problem at the start or end of a weld. A sudden wire jab, a start that sputters before settling, or a wire end that sticks to the work may point to run-in settings. A wire end that freezes into the puddle, or one that retreats so far it is difficult to restart, may point to burnback.
First rule out basic setup faults. Confirm that the wire diameter matches the drive rolls and contact tip, the wire feeds smoothly, the work clamp has a clean connection, and the voltage and wire speed suit the material and joint. Poor wire feeding or incorrect settings can look like a timing problem. On a new welder, consult its manual before changing controls; some machines apply automatic start or stop functions that interact with these adjustments.
How to set run-in
Start with the manufacturer’s recommended setting, or the factory default if the machine has one. If the wire hits the plate hard before the arc settles, reduce run-in speed or increase the run-in period slightly, depending on the control. Make small changes and test on scrap of the same thickness and position. A change of about 5–10% is a useful first step on a percentage control; for a numbered dial, move only one increment.
If the wire seems to creep toward the work without striking an arc, or the start is weak and delayed, run-in may be too slow. Increase it gradually. Do not use a slow run-in to disguise excessive stickout, poor grounding, or an unsuitable voltage and wire-speed combination. Those faults will still affect the weld after the arc starts.
Keep the torch angle and contact-tip-to-work distance consistent during tests. On thin sheet, a hard start can burn through or leave a crater; on thicker plate, it may simply create an uneven first spot. If the welder has no run-in control, start with the torch positioned close to the joint and use a steady trigger pull rather than changing technique mid-start.
How to set burnback
Begin at the factory setting. If the wire sticks to the work when you release the trigger, increase burnback a small amount. If the wire end burns back into the contact tip, reduce it. Make one change at a time, then make several short test welds. A clean stop should leave the wire close enough to the tip for an easy restart, without being fused to the puddle.
Burnback is usually a short interval, often measured in fractions of a second, but the correct value depends on the machine, wire, and setup. Do not assume a particular dial number or time is universal. A long delay may overheat the wire end or contact tip, especially with high output or repeated short welds. If adjustment does not solve sticking, check for worn or incorrectly sized tips, erratic feeding, and a dirty or loose connection.
Symptoms and adjustments
| Symptom | Likely control to check | First adjustment or check |
|---|---|---|
| Wire jabs the work at arc start | Run-in | Reduce run-in speed slightly; verify wire speed and voltage |
| Start is weak or arc takes time to establish | Run-in | Increase run-in slightly; check ground and wire feed |
| Wire freezes into the work at release | Burnback | Increase burnback slightly; inspect the tip and feed path |
| Wire burns back into the contact tip | Burnback | Reduce burnback; check tip size and feeding consistency |
A practical test routine
Use clean scrap and the same wire, gas, and thickness as the job. Make three short welds with the current settings and note the results. Change one control by one small step, repeat, and compare the starts and wire ends. If the results vary from weld to weld, investigate feeding, torch positioning, and electrical connections before making further timing changes.
For frequent fabrication work, a machine with adjustable run-in and burnback can be useful. For occasional repairs, a welder with fixed or automatic timing may be perfectly adequate if it starts and stops cleanly with your wire and material. Compare MIG welders with adjustable run-in and burnback if you need those controls, but do not pay extra for them unless your work benefits from fine adjustment.
Whatever the controls, wear a properly rated helmet, gloves, and protective clothing, and keep flammable material away from the work area. The goal is not a particular dial position; it is a consistent start, a clean stop, and a wire end that is ready for the next weld.