Three gases, three logics
Assist gas ejects molten metal, protects the lens, and influences the cutting chemistry. The wrong gas means a blackened edge at best — halved speed and doubled cost at worst.
Oxygen (O₂) — the carbon-steel choice
- Exothermic oxidation with iron adds energy, markedly raising speed on thick carbon steel
- Leaves an oxide (dark) edge — note before welding or coating
- Low gas cost, modest pressure
Nitrogen (N₂) — stainless & aluminium
- Inert blowing, no reaction — oxide-free bright edge, weld-ready
- Needs high pressure (15–25 bar) and high power; heavy consumption, higher cost
- The only answer for premium stainless cosmetic parts
Air — the economical option
- ~78% N / 21% O, lowest cost (just a compressor plus drying/filtration)
- Great for thin carbon steel, galvanised and aluminium in volume
- Must be dry and oil-free, or lens life and edge quality suffer
| Gas | Best for | Edge | Cost/m |
|---|---|---|---|
| Oxygen | Medium/thick carbon steel | Oxidised dark | Low |
| Nitrogen | Stainless / aluminium | Oxide-free bright | High |
| Air | Thin-sheet volume | Moderate | Lowest |
In practice a shop mixes all three by job type. Select on material, thickness, cosmetic requirement and gas cost per metre — not cutting speed alone.