Investing in an industrial laser cutting machine can significantly improve cutting speed and precision in a metal fabrication shop. Once the machine is installed, many plant managers face the ongoing challenge of controlling consumable costs.
Assist gas accounts for 30% to 50% of operating expenses when electricity and equipment depreciation are excluded. Your choice of nitrogen (N₂), oxygen (O₂), or compressed air affects the cost per linear meter cut, the edge finish, whether dross forms, and whether the part needs further polishing or shot blasting.
This guide covers how each gas works, its benefits, and where it performs best so you can get the most out of your fiber laser metal cutting machine.
1. Nitrogen Cutting for Clean, Oxide-Free Edges
Nitrogen cutting is an inert fusion process also known as melt and blow. The fiber laser beam melts the metal, and high-pressure nitrogen (14 to 22 bar) blows the molten metal out of the kerf.
Key benefits
- Clean, oxide-free edges. The inert atmosphere preserves the metal’s natural color and leaves the cut edge free of scale and oxidation.
- Parts ready for welding or painting. Parts cut with nitrogen can go directly to electrostatic painting or TIG/MIG welding without extensive degreasing or prior sanding.
- Faster cutting in thin sheet metal. Nitrogen maximizes cutting speed in 0.5 to 4 mm sheets of stainless steel, aluminum, brass, and copper.
Limitations
Nitrogen cutting consumes large volumes of gas at high pressure. When cutting thick carbon steel plate, the cost of liquid nitrogen supplied in cylinders or a cryogenic tank can sharply increase the cutting cost per meter.
2. Oxygen Cutting for Thick Carbon Steel
Oxygen cutting relies on an exothermic thermochemical reaction. As oxygen blows molten material out of the cut, it reacts with the iron in the steel, releasing additional heat that helps the laser beam melt the metal.
Key benefits
- Lower pressure and gas consumption. Oxygen cutting uses pressures of 0.5 to 2.5 bar, which significantly reduces the volume of gas consumed per hour.
- Ability to cut thick material. Oxygen is the standard assist gas for medium- to heavy-gauge carbon steel, including A36 steel, rectangular steel tubing (PTR), and structural plate, at thicknesses from 6 mm to 25 mm or more.
- Lower laser power requirements. Machines rated at 1.5 to 3 kW can cut thick material that would require substantially more power with nitrogen.
Limitations
Combustion leaves a dark oxide layer on the cut edges. Remove this layer before painting because the paint can peel over time as the oxide scale flakes off.
3. Lower Cutting Costs with Filtered Compressed Air
Compressed air contains about 78% nitrogen and 21% oxygen. It has become a popular option for contract fabrication shops with the development of high-power laser sources (6 to 12 kW and above) and high-efficiency filtration systems.
Key benefits
- Lower consumable costs. With a dedicated rotary screw compressor, a refrigerated air dryer, and coalescing filters, the cost of supplying assist gas comes down to the electricity the compressor uses.
- Fast production. In thin to medium sheets of carbon steel and stainless steel (0.8 to 4 mm), compressed air achieves cutting speeds close to those of pure nitrogen.
- Quick payback. Under heavy use, the compressor and drying equipment typically pay for themselves within 3 to 6 months.
Limitations
Compressed air must be exceptionally clean and meet ISO 8573-1 Class 1 for oil and water. Any trace of water or moisture in the gas line will immediately burn the laser head’s protective lens. Compressed air also leaves a slight yellow-brown discoloration on stainless steel edges.
4. Assist Gas Selection by Material and Thickness
Use this reference table when setting up your machine for a cut.
Material
Edge quality
Operating cost
Stainless steel
Aluminum or brass
Carbon steel
Carbon steel
Carbon steel
Bright silver, 100% oxide-free
Clean, with no dross on the underside
Straight edge with slight oxidation
Dark edge with an oxide layer
Minimal dross and a perpendicular cut
High due to continuous gas use
High
Very low w/ compressed air
Low to moderate
Low (low pressure required)
Thickness
0.5 to 6 mm
All thicknesses
0.8 to 3 mm
4 to 10 mm
Over 12 mm
Recommended gas
Nitrogen (N₂)
Nitrogen (N₂)
Compressed air or N₂
Compressed air or O₂
Oxygen (O₂)
5. Optimizing Your Gas Supply
Follow these three practical tips to get the most out of your industrial laser cutting machine.
- Monitor nitrogen purity. If you use an on-site PSA nitrogen generator, maintain a minimum purity of 99.99% to prevent discoloration on stainless steel.
- Install three-stage filtration for compressed air. Equip the air line with a water separator, a coalescing filter rated down to 0.01 microns, and a desiccant or refrigerated dryer with a dew point below freezing.
- Adjust the nozzle diameter. Use single nozzles for oxygen cutting and double or high-speed nozzles for nitrogen and compressed air.
Improve Efficiency in Your Metal Fabrication Shop
Choosing the right laser cutting assist gas helps reduce the cost per part and deliver a professional finish to your customers.
At GearMax Pro, we offer a full line of fiber laser metal cutting machines, including the G, GI, HM, K, L, P, and S series. These machines are designed for energy-efficient operation with nitrogen, oxygen, or compressed air systems.
- Want to lower cutting costs at your plant? View the specifications for our industrial laser cutting machines or ask our manufacturing specialists for a personalized technical consultation.
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