Key Takeaways
- Fiber laser: Best for sheet metal 0.5–20 mm. Fastest speed, best edge quality, narrow kerf, but highest capital cost and limited to <25 mm on most machines.
- Plasma: Best for carbon steel 6–80 mm where edge finish is secondary. Lower capital cost; high-definition plasma approaches laser quality on thin material.
- Waterjet: The only truly universal process — cuts virtually any material with no HAZ. Use it for heat-sensitive materials, composites, titanium, and thick sections where thermal processes fail.
- Operating cost: laser < plasma < waterjet on a per-part basis for most sheet metal work.
- For most general fabricators buying their first machine: a 3–6 kW fiber laser handles 80% of typical sheet metal work optimally.
Master Comparison Table
| Parameter | Fiber Laser (6 kW) | HD Plasma | Waterjet (60k psi) |
|---|---|---|---|
| Speed on 6mm mild steel | 6,500 mm/min | 2,500 mm/min | 400–600 mm/min |
| Speed on 12mm mild steel | 2,800 mm/min | 1,800 mm/min | 200–350 mm/min |
| Kerf width (6mm MS) | 0.2–0.4 mm | 1.5–2.5 mm | 0.8–1.1 mm |
| Tolerances | ±0.1 mm | ±0.5–1.0 mm | ±0.1–0.2 mm |
| Heat-affected zone | Minimal (0.1–0.3 mm) | Moderate (1–3 mm) | None |
| Max thickness (carbon steel) | ~25 mm (12 kW: ~40 mm) | 80 mm | 200+ mm |
| Aluminium edge quality | Excellent (N₂ assist) | Fair (oxide layer) | Excellent |
| Stainless quality | Excellent (N₂ assist) | Good (HD) | Excellent |
| Non-metals / composites | No (fire hazard / fumes) | No | Yes |
| Capital cost (entry level) | $120k–$250k | $60k–$180k | $100k–$250k |
| Operating cost ($/hr) | $8–$20 | $15–$35 | $25–$60 |
| Consumable wear item | Nozzle, lens (~1000 hrs) | Nozzle/electrode (~6–8 hrs) | Nozzle, orifice, abrasive |
Speeds are representative. Actual values depend on machine configuration, assist gas, and material grade.
Fiber Laser: The Sheet Metal Workhorse
A fiber laser generates the cutting beam through a rare-earth doped optical fibre (typically ytterbium), delivering wall-plug efficiency of 25–35% — roughly 3× better than CO₂ lasers. The beam wavelength (1.06 µm) is well-absorbed by metals, enabling fast piercing and cutting. Modern machines with pallet changers, automatic nozzle changing, and sheet loading handle 24/7 unattended operation.
Power vs thickness guide (mild steel, N₂ assist):
| Power | Max Thickness (MS) | Speed at 3mm | Speed at 6mm |
|---|---|---|---|
| 1.5 kW | 8 mm | 6,000 mm/min | 2,000 mm/min |
| 3 kW | 12 mm | 9,000 mm/min | 4,500 mm/min |
| 6 kW | 20 mm | 15,000 mm/min | 6,500 mm/min |
| 12 kW | 30 mm | 25,000 mm/min | 12,000 mm/min |
| 20 kW | 40 mm | 35,000 mm/min | 18,000 mm/min |
See our full fiber laser wattage guide for detailed speed tables across all materials.
High-Definition Plasma: Best for Thick Carbon Steel
Modern high-definition (HD) plasma systems (Hypertherm XPR series, Lincoln Electric Plasma) use a constricted arc and secondary gas to focus the plasma column, achieving tolerances of ±0.5 mm and surface finish that approaches laser quality on 6–12 mm carbon steel. The consumable cost is higher than laser (nozzle/electrode sets wear in 6–8 hours of cutting) but capital cost is 40–60% lower.
Plasma advantage over laser: penetrating 25–80 mm carbon steel at commercially viable speed. A 300A plasma system cuts 50 mm mild steel at 300 mm/min — no laser in the same price range can match this.
Waterjet: The Universal Cutter
Abrasive waterjet uses a 55,000–90,000 psi water stream mixed with garnet abrasive to cut by erosion. No thermal process is involved, which means:
- No heat-affected zone (critical for aerospace titanium, pre-hardened steel, and composites)
- No change in material properties — cut titanium or hardened tool steel without annealing
- Cuts glass, ceramics, stone, rubber, food, and composites that would burn or crack under heat
The abrasive cost ($0.20–$0.40/lb of garnet) is the dominant operating expense — typically $25–$60/hour including pump maintenance. For high-value, hard-to-cut materials this is easily justified; for standard mild steel sheet, waterjet is economically uncompetitive against a fiber laser.
Which Process: Decision Guide
| Situation | Best Process | Why |
|---|---|---|
| Sheet metal shop, MS/SS/Al up to 20mm | Fiber Laser (3–6 kW) | Fastest, best finish, no HAZ on thin material |
| Structural fabricator, carbon steel 6–50 mm | HD Plasma | Lower capital, adequate quality at heavy thickness |
| Aerospace, titanium, CFRP, pre-hardened steel | Waterjet | Only process with zero HAZ, no metallurgical change |
| Very thick plate (>50 mm carbon steel) | Plasma or Oxy-fuel | Laser economics deteriorate above 25–30 mm |
| Mixed material shop (metal + non-metal) | Waterjet + Laser | Waterjet for composites/ceramics, laser for metal speed |
Frequently Asked Questions
Which cutting process produces the best edge finish?
Fiber laser with nitrogen assist produces the best edge finish on aluminium and stainless — a bright, oxide-free surface. On carbon steel with oxygen assist, a thin oxide layer forms but edge finish is still better than HD plasma. Waterjet produces a matte abraded finish that is acceptable for most structural applications but not for surfaces requiring subsequent sealing.
Can fiber lasers cut reflective metals like copper and brass?
Modern fiber lasers (1.06 µm wavelength) cut copper, brass, and aluminium much more effectively than CO₂ lasers because the metal absorbs the shorter wavelength better. However, copper in particular reflects a significant fraction of the beam back — most fiber laser OEMs now offer back-reflection protection (BPP monitoring) as standard. Always check your machine's copper/brass capability specification before attempting to cut these materials.