Cause reference table
| Symptom | Common cause | How to check | What to do |
|---|---|---|---|
| Porosity on the weld surface | Insufficient or incorrect shielding gas flow | Check the flow meter and the line for leaks | Adjust flow; replace leaking hose |
| Porosity with a dull weld colour | Contaminated surface: oil, paint, rust, moisture | Clean one section and weld a comparison bead | Clean before welding |
| Burn-through on thin sheet | Too much power or dwell time | Reduce power, increase travel speed | Reset parameters for that thickness |
| Burn-through at part edges | Poor heat sinking at the edge | Check whether burn-through is always at an edge | Reduce energy approaching the edge; change weld direction |
| Lack of fusion, weld only bridging the surface | Joint gap too wide | Clamp and measure the gap | Re-fixture for a tight fit; or use wire feed |
| Lack of fusion on T-joints | Incorrect gun angle | Review angle and direction | Adjust the gun angle; test on scrap |
| Quality varies between operators | Different hand travel speed | Have two operators weld the same sample | Training; or use a fixture that constrains the travel |
The root cause most often missed: joint gap
Laser welding concentrates energy into a very small area. If the two edges do not meet, the energy passes through the gap instead of melting the metal together. Adding power in that situation only burns more; it does not produce a better weld.
This is why laser-cut parts weld far more easily than parts cut by hand or plasma. If your joints are inconsistent, good fixturing improves results considerably more than extra power does.
Where the gap is genuinely wide and cannot be fixtured any tighter, wire feed is how metal is added — that is its function, not a decorative accessory.
The second common misdiagnosis
Many shops adjust parameters when the problem is on the surface.
Oil, paint, rust and moisture all cause porosity. If parts have just come out of a damp store, or were cut and still carry oil, the weld will be porous even with entirely correct settings. Clean one section and weld a comparison bead — two minutes, and it eliminates a whole branch of causes.
Safety — not an optional item
Handheld laser welding requires, from the first day of operation:
- Eyewear matched to the wavelength for everyone in the area, not only the person holding the gun
- Screens or an enclosure so reflected beam does not leave the area
- Local weld fume extraction
Laser reflected off a bright metal surface still carries enough energy to injure eyes. This is why laser welding must not be done in an open area with people walking through.
Send us your sample part. We will weld it with your real material and your real joint, send the sample back for you to judge — and say plainly if the problem sits in the cutting stage rather than in the welder.