Key Takeaways
- 1.5–3 kW: Thin sheet specialists — fast on 0.5–6 mm, limited above 10 mm. Lowest capital and operating cost.
- 6 kW: The current "sweet spot" for mixed job shops — handles mild steel to 20 mm, stainless to 15 mm, aluminium to 12 mm at commercially viable speeds.
- 12–20 kW: High-volume or thick-plate shops. Dramatically faster on 6–30 mm; overkill for thin-sheet work.
- Above 6 kW, nitrogen consumption for clean-edge stainless cutting rises proportionally — factor this into operating cost.
- BPP (beam parameter product) quality matters as much as wattage — a premium 6 kW source may outperform a budget 10 kW on thin material edge quality.
Power vs Thickness: The Fundamental Relationship
Cutting speed and maximum thickness are not linear with power. Doubling power from 3 kW to 6 kW does not double the cutting speed — it typically increases speed by 40–80% on thin material and extends the maximum workable thickness by 6–10 mm on mild steel.
The relationship flattens at higher power: going from 6 kW to 12 kW typically adds 30–50% more speed on thin material. Beyond 20 kW, speed gains on thin sheet are diminishing and beam quality (not watts) becomes the limiting factor.
Mild Steel Cutting Speeds by Power Level
| Thickness | 1.5 kW | 3 kW | 6 kW | 12 kW | 20 kW |
|---|---|---|---|---|---|
| 1 mm | 10,000 | 18,000 | 30,000+ | 40,000+ | 50,000+ |
| 2 mm | 6,000 | 11,000 | 20,000 | 28,000 | 35,000 |
| 3 mm | 3,500 | 7,000 | 13,000 | 20,000 | 25,000 |
| 6 mm | 1,200 | 2,800 | 6,500 | 11,000 | 16,000 |
| 10 mm | 400 | 1,100 | 3,200 | 6,500 | 10,000 |
| 15 mm | — | 400 | 1,500 | 3,800 | 6,500 |
| 20 mm | — | — | 600 | 2,000 | 4,000 |
| 25 mm | — | — | 200 | 1,000 | 2,500 |
| 30 mm | — | — | — | 400 | 1,200 |
Speeds in mm/min using O₂ assist for mild steel. These are representative mid-range values — actual speeds depend on machine optics, nozzle condition, and material grade. — = not commercially viable at that power.
Stainless and Aluminium Speed Summary
| Material / Thickness | 3 kW (N₂) | 6 kW (N₂) | 12 kW (N₂) |
|---|---|---|---|
| Stainless 304, 2 mm | 4,500 | 9,000 | 18,000 |
| Stainless 304, 6 mm | 900 | 2,800 | 5,500 |
| Stainless 304, 10 mm | 200 | 900 | 2,200 |
| Aluminium 5052, 3 mm | 5,000 | 10,000 | 18,000 |
| Aluminium 5052, 6 mm | 1,800 | 4,500 | 9,000 |
| Aluminium 5052, 12 mm | 200 | 900 | 2,500 |
All stainless and aluminium values assume nitrogen (N₂) assist gas for oxide-free edge finish.
Choosing Your Power Level
| Shop Profile | Recommended Power | Why |
|---|---|---|
| Sheet metal fabricator, primarily 0.5–6 mm, high mix | 3–6 kW | Maximum speed on thin material, lower gas cost |
| General job shop, 0.5–20 mm, mixed material | 6 kW | Best capability-to-cost ratio for mixed work |
| Heavy plate, 10–30 mm carbon steel, high volume | 12–20 kW | Significant speed advantage justifies higher capital |
| Aluminium specialist, 1–15 mm | 6–12 kW | Al absorbs less beam — higher power compensates |
| Entry-level / low volume budget shop | 1.5–3 kW | Lowest capital and operating cost for thin work |
Operating Cost by Power Level
Higher wattage means more electricity and higher gas consumption (especially N₂ for stainless/aluminium). Here are representative hourly costs for North American operating conditions:
| Power | Electricity ($/hr) | N₂ assist ($/hr) | Consumables ($/hr) | Total approx ($/hr) |
|---|---|---|---|---|
| 3 kW | $3–$5 | $8–$15 | $2–$3 | $13–$23 |
| 6 kW | $6–$9 | $12–$22 | $2–$4 | $20–$35 |
| 12 kW | $12–$18 | $18–$35 | $3–$5 | $33–$58 |
| 20 kW | $20–$30 | $25–$50 | $4–$7 | $49–$87 |
Assumes N₂ on-site generation. Bottled N₂ costs 3–5× more per m³. Electricity at $0.12/kWh. Consumables: nozzles, lenses, windows.