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Assist gas strategy: cost, quality, and speed trade-offs
Select O₂/N₂/Air by material and thickness to balance edge quality with total job cost and throughput.
FundamentalDuration: 16 min
1) Choose gas by material, thickness, and outcome
Match gas to material to achieve the required edge quality at the lowest total cost.
| Material | Typical Thickness | Recommended Gas | Outcome |
|---|---|---|---|
| Mild steel | 1–12 mm | O₂ (most), N₂ for paint-ready edges | O₂ fastest; oxide layer present. N₂ is slower but clean edge, no oxide. |
| Stainless steel | 0.8–8 mm | N₂ | Bright, clean edge. Prevents oxidation and discoloration. |
| Aluminum | 1–6 mm | N₂ or Air (thin) | N₂ for best edge. Air acceptable on thin sheet with minor burr risk. |
| Galvanized steel | 1–4 mm | N₂ | Minimizes coating burn; watch fumes; ensure extraction. |
- Finish requirement: Paint-ready or food-grade edges → prefer N₂ even on mild steel.
- Throughput focus: General fabrication with deburr step → O₂ on mild steel for speed.
- Cost control: Thin (<2 mm) aluminum or mild steel → consider Air; validate edge quality first.
2) Quantify gas cost and total job economics
Cost Formulas
Gas cost per hour = Flow (m³/hr) × Price ($/m³)
Gas cost per job = Gas cost/hr × Cut time (hr)
Total job cost impact = (Gas + Energy + Consumables) ÷ Quantity
| Gas | Typical Flow | Price | Cost/hr (example) | Notes |
|---|---|---|---|---|
| O₂ | 6–15 m³/hr | $0.50–$1.50/m³ | $3–$23 | Lower flow than N₂; fastest on mild steel. |
| N₂ | 15–35 m³/hr | $0.30–$1.20/m³ | $5–$42 | Higher flow; clean edge, no oxide. |
| Air | 10–25 m³/hr | Low (compressor) | $1–$6 (electricity) | Very low gas cost; validate edge quality. |
3) Nozzle, pressure, and parameter guidelines
- Nozzle diameter: 1.0–2.0 mm common; larger for thicker material to maintain flow.
- Pressure: O₂: 0.3–1.5 bar; N₂: 8–20 bar; Air: 5–10 bar (typical ranges—tune per machine).
- Stand-off: Maintain correct distance to minimize dross and taper; auto height control recommended.
- Clean supply: Ensure dry, oil-free Air and N₂; filter to protect optics and improve edge quality.
4) Quality vs speed: when to choose O₂ / N₂ / Air
- O₂ (mild steel): Best for speed and thick sections; oxide must be removed before painting/welding.
- N₂ (stainless/aluminum): Best edge quality; use when cosmetic finish or corrosion resistance matters.
- Air (thin sheet): Lowest cost; acceptable for non-cosmetic parts; test for minor burr/discoloration.
5) Safety and supply management
- Ventilation: Use proper extraction for O₂ on mild steel and galvanized materials (fume control).
- Cylinders vs bulk: High N₂ consumption favors bulk tanks or N₂ generators; review ROI on annual usage.
- Leak checks: Regularly inspect lines and fittings; leaks raise gas cost and reduce cut quality.
6) Case studies: choosing the right gas
Mild Steel 6 mm, Painted Parts
- O₂: Fastest cut, oxide removal adds 30–60 sec/part deburr → total time increases.
- N₂: Slightly slower but paint-ready edge → saves rework, better total cost on small/medium batches.
Stainless 3 mm, Visible Panels
- N₂ provides bright edge; avoids discoloration and post-processing → shortest end-to-end lead time.
Aluminum 2 mm, Internal Brackets
- Air viable with minor burr; if cosmetic surfaces needed, switch to N₂ to avoid rework.