Handheld Fiber Laser Cutting Troubleshooting Guide (800W / 1200W)
This guide is built from real cutting tests using both 800W and 1200W handheld fiber lasers. on 1–4 mm stainless steel, carbon steel, aluminum and brass.
Over time, we noticed that most operators run into the same issues—burrs, black edges, incomplete cuts, unstable sparks, and so on.
So instead of guessing, we summarized the actual cutting window and the exact parameter tweaks that reliably fix each problem.
Everything here comes from real use, not theory.
Baseline Cutting Window (from 800W / 1200W Data)
| Thickness | 800W Speed | 1200W Speed | N₂ Pressure | Peak Power |
|---|---|---|---|---|
| 1.0 mm | 12 mm/s | 18 mm/s | 6–8 bar | 65–75% |
| 2.0 mm | 8 mm/s | 12 mm/s | 6–8 bar | 75–85% |
| 3.0 mm | 6 mm/s | 8 mm/s | 6–8 bar | 85–95% |
| 4.0 mm | – | 6 mm/s | 6–8 bar | 95% |
Rule of thumb: Thicker plate → slower speed → higher peak power → nitrogen must stay at 7–8 bar.
For larger-volume jobs or thicker material, a dedicated cutting machine is far more stable: Industrial Laser Cutting Machines (GWEIKE).
Top 10 Handheld Cutting Problems & Fixes
1. Not Cutting Through
Symptoms: Backside not separated, intermittent uncut sections.
Common Causes:
- Cutting speed too fast for plate thickness.
- Peak power too low.
- N₂ pressure below 6 bar or unstable.
- Incorrect focus position.
Corrections:
- 2 mm → reduce speed from 12 → 8 mm/s
- 3 mm → reduce from 8 → 6 mm/s
- Increase peak power: 85% → 95%
- Lock nitrogen at 7–8 bar
2. Burr (Bottom Slag)
Causes:
- N₂ pressure too low.
- Speed too slow → molten pool accumulates.
- Focus too low.
Corrections:
- Increase pressure to 8 bar
- Slightly increase speed (e.g., 6 → 8 mm/s)
- Shift focus upward 0.1–0.2 mm
Many cutting issues actually come from incorrect focus height. If you want a deeper breakdown of how 50 mm / 63.5 mm / 100 mm lenses affect kerf shape, see: Focus Lens Guide (50 / 63.5 / 100 mm).
3. Black Edge (Oxidation)
Causes:
- Insufficient nitrogen shielding.
- Speed too low.
- Power too high.
Corrections:
- Use 99.9% high-purity N₂
- Increase cutting speed
- Reduce peak power: 95% → 85%
4. Ripple Lines
Causes: Hand instability, PWM mismatch, incorrect speed.
Corrections:
- Keep PWM at 1000 Hz
- Scanning frequency: 5 Hz
- Use table-recommended speeds
5. Nozzle Burn
Corrections:
- Nozzle distance 0.8–1.0 mm
- Peak power 95% → 85%
- N₂ at 7–8 bar
6. Rough Edge
- Reduce speed by ~20%
- Increase nitrogen pressure by 1 bar
- Adjust focus ±0.1–0.3 mm
Maintaining the correct nitrogen pressure is critical for clean stainless steel cuts. For CO₂ systems, airflow behaves differently — we summarized the mild-steel rules here: Mild Steel Settings for CO₂ Lasers.
7. Unstable Sparks (Aluminum / Brass)
- Reduce peak power by 10%
- N₂ stable at 8 bar
- Increase speed (6 → 8 mm/s)
8. Whitish Surface (Aluminum)
- Increase peak power
- Reduce speed (8 → 6 mm/s)
- Maintain 7–8 bar N₂
9. Interrupted / Unstable Cutting
- Check regulator stability
- Keep 7 bar under continuous flow
- Lower speed slightly
10. Kerf Too Wide
- Increase speed (6 → 8 mm/s)
- Reduce power (95% → 85%)
- Raise focus 0.1–0.2 mm
Quick Reference Table
| Problem | Main Cause | Correction |
|---|---|---|
| Not cutting through | Speed too fast / power too low / gas low | Lower speed; 95% power; 7–8 bar N₂ |
| Burr | Weak gas / molten pool | 8 bar gas; increase speed |
| Black edge | Oxidation | Increase speed; reduce power |
| Ripple | PWM imbalance | PWM 1000 Hz; table speed |
| Nozzle burn | Nozzle too close | 1 mm distance; reduce power |
| Rough edge | Focus error | Slow speed; increase pressure |
| Unstable sparks (Al) | High reflectivity | Lower power; faster speed |
| Whitish cut (Al) | Low energy | Increase power; reduce speed |
| Interrupted cutting | Gas unstable | Lock 7 bar; reduce speed |
| Wide kerf | High power / low speed | Increase speed; reduce power |
FAQ
-
What nitrogen pressure works best for handheld cutting?
In most cases, a stable 6–8 bar is enough, but for stainless steel you’ll get noticeably cleaner edges if you keep it around 7–8 bar during continuous flow. -
Can a handheld fiber laser cut 4 mm steel?
Yes — with a 1200W handheld unit it’s possible. The typical sweet spot is around 6 mm/s with high peak power and steady nitrogen pressure. -
Why do I get burr on the bottom edge?
Burr usually means the nitrogen isn’t blowing the molten metal out fast enough. Either the pressure is a bit low, or the cutting speed is too slow and the melt is pooling. -
Why are the edges turning black?
Black edges come from oxidation. That happens when the nitrogen shielding isn’t strong enough or when you move too slowly, giving the material extra heat time. -
What’s the difference between desktop laser cutters and industrial machines, and which one is suitable for small workshops?
For makers and small workshops, here’s a simple intro comparing consumer-level machines: Desktop Laser Cutting Machine Guide.
