22 Years of Making
22 Years of Making, UP TO 62% OFF
In this guide
Use oxygen for thicker carbon steel when oxidation-assisted penetration is the priority. Use nitrogen for bright, low-oxidation edges on stainless steel, aluminum, brass and selected thin carbon steel. Use clean, dry compressed air when operating cost and simplicity matter more than a perfectly oxide-free edge. The best gas changes with material, thickness, machine power, edge requirements and downstream work.
Quick Answer: Air, Nitrogen or Oxygen?
Choose the required edge and complete process—not the gas name by itself.
| Material or Requirement | Best Starting Gas | Why |
|---|---|---|
| Thin carbon steel, cost priority | Compressed air | Can be economical where a lightly oxidized edge is acceptable |
| Thicker carbon steel | Oxygen | Exothermic oxidation adds cutting energy and extends penetration |
| Bright carbon-steel edge | Nitrogen | Reduces oxidation, subject to machine power and verified thickness capability |
| Stainless steel, high-quality edge | Nitrogen | Common choice for bright, low-oxidation results |
| Stainless steel, cost priority | Compressed air | Lower gas cost direction, with a darker or lightly oxidized edge |
| Aluminum or brass | Nitrogen or verified air preset | Controls oxidation while ejecting molten material; reflective-metal controls remain essential |
| Parts requiring minimal edge cleanup | Nitrogen | May reduce oxidation-related finishing and rework |
| Hidden edges or parts already being ground | Air or oxygen as applicable | Lower gas cost may matter more than edge appearance |
What Does Assist Gas Do in Fiber Laser Cutting?
Assist gas is not simply an air stream that removes smoke. It clears molten metal from the kerf, controls oxidation at the cut front, influences edge color and dross, and helps protect the process zone around the nozzle and optics. The chemical behavior of the gas can also change how the cut is created.
- Eject melt: clear molten metal from the kerf to prevent dross and incomplete penetration.
- Control chemistry: oxygen promotes oxidation, nitrogen limits it and air creates an intermediate reaction.
- Set edge condition: change oxide, color, striation and required cleanup.
- Stabilize the process: work with the specified nozzle, focus, pressure, flow and speed.
Compressed Air for Fiber Laser Cutting
Compressed air is mostly nitrogen but contains enough oxygen to create a more reactive cut than high-purity nitrogen. It can provide a practical balance of melt ejection, moderate oxidation and operating cost for thin sheet and small-shop production.
Advantages of compressed air
- Reduces dependence on delivered high-purity gas.
- Fits workshops prioritizing simpler day-to-day gas logistics.
- Can be economical when edges will be hidden, ground or coated.
- Works with the optional GWEIKE air-supply approach on MCore and with published M Series air presets.
Limitations of compressed air
- It is not oxide-free; stainless edges may appear darker or discolored.
- Compressor outlet pressure does not guarantee pressure and flow at the cutting head.
- Water, oil and particles can destabilize the cut and contaminate components.
- Electricity, filters, condensate handling and maintenance mean air is not free.
Nitrogen for Fiber Laser Cutting
Nitrogen is used primarily to eject molten material while limiting oxidation. It is the usual first choice when stainless steel, aluminum or brass needs a bright edge, and it can also produce low-oxidation edges on thin carbon steel within the machine’s verified range.
Advantages of nitrogen
- Produces a brighter, lower-oxidation edge on compatible stainless steel.
- Supports aluminum and brass cutting without intentionally adding oxygen.
- May simplify downstream welding, coating or inspection when oxide is undesirable.
- Provides a useful quality baseline for comparing compressed-air edges.
Limitations of nitrogen
- Often requires high pressure and substantial gas flow.
- Cylinder, dewar, bulk supply or nitrogen-generator costs must be included.
- Purity and dynamic pressure affect oxidation and edge consistency.
- It does not add the exothermic cutting energy that oxygen provides on carbon steel.
- Higher gas cost may not be justified when edges will be ground.
GWEIKE’s M Series factory guide specifies liquid nitrogen purity of at least 99.999% and uses high-pressure N₂ references for selected materials. Those conditions belong to that platform and parameter table; they should not be copied automatically to a different machine.
Oxygen for Fiber Laser Cutting
Oxygen reacts with hot carbon steel and releases additional energy at the cut front. This oxidation-assisted mechanism allows a lower-power fiber source to cut thicker carbon steel than it could through inert melt ejection alone.
Advantages of oxygen
- Extends carbon-steel penetration and thickness capability.
- Supports MCore’s currently published 1–5mm carbon-steel parameter range.
- Supports thicker-carbon-steel rows in the M800/M1200 CNC parameter guide.
Limitations of oxygen
- Creates an oxidized, darker carbon-steel edge.
- Introduces elevated combustion and fire risk.
- Requires oxygen-compatible components and trained handling.
- Is not the default choice for stainless steel, aluminum or brass.
More oxygen pressure is not automatically better. Oxygen cutting depends on a controlled reaction, nozzle flow and correct focus. The GWEIKE tables pair oxygen with different pressures, double nozzles, speeds and focal positions than compressed air or nitrogen.
Choose Assist Gas by Material
Carbon steel
Carbon steel offers the widest gas choice: air for verified cost-sensitive thin sheet, nitrogen for low oxidation within the machine’s capability and oxygen as thickness increases.
The faster gas changes with thickness and power. In GWEIKE’s MCore table, compressed air has the higher listed speed at 1mm, the 2mm air value overlaps the oxygen speed range, and oxygen has the higher listed speed at 3mm. The published 4mm and 5mm rows are oxygen only. See the exact MCore O₂ vs Air comparison rather than assuming oxygen always cuts faster.
Stainless steel
Use nitrogen as the quality baseline for a bright, low-oxidation edge. Air can be economical for thin stainless when discoloration or later finishing is acceptable.
MCore currently has published compressed-air parameters for 1–3mm stainless steel. Its product positioning mentions nitrogen for cleaner stainless edges, but a complete public MCore nitrogen parameter table is not currently available. Request a verified test instead of inventing N₂ speed or pressure values.
Aluminum
Nitrogen is the quality direction for aluminum on M Series; MCore has selected thin-aluminum air references. Reflection controls, focus and nozzle alignment remain essential.
Brass
Nitrogen supports cleaner brass cutting on M Series, while MCore has selected thin-brass air references. Alloy and reflection controls still require testing.
| Material | Air | Nitrogen | Oxygen |
|---|---|---|---|
| Carbon steel | Thin sheet and cost priority | Thin, low-oxidation edge within verified capability | Thicker sheet and oxidation-assisted penetration |
| Stainless steel | Economical, lightly oxidized edge | Preferred quality direction | Not the normal choice; severe oxidation risk |
| Aluminum | Possible with verified thin-sheet preset | Preferred quality direction | Not the default choice |
| Brass | Possible with verified thin-sheet preset | Preferred quality direction | Not the default choice |
Edge Quality and Downstream Processing
| Factor | Compressed Air | Nitrogen | Oxygen |
|---|---|---|---|
| Oxidation direction | Moderate | Lowest when purity and pressure are correct | Intentional and highest |
| Typical edge appearance | Darker or lightly oxidized | Brighter and cleaner | Dark oxidized carbon-steel edge |
| Thicker carbon steel | Limited by machine and flow | Power- and pressure-intensive | Usually the strongest direction |
| Stainless appearance | Acceptable when discoloration is allowed | Usually preferred | Not recommended as the standard process |
| Gas-cost direction | Often lower after system investment | Often higher | Depends on supply and finishing cost |
| Post-processing | May require oxide cleanup | Often reduced | Oxide removal commonly required |
Before welding
Oxide and dross can affect fit-up and welding. Evaluate O₂-cut carbon steel and air-cut edges for cleanup; accept parts against welding requirements, not color alone.
Before powder coating or painting
Visual cleanliness does not prove coating readiness. Validate oxide removal, pretreatment and adhesion against the coating specification.
Visible finished edges
Nitrogen can justify its cost on visible edges; air may win when edges are hidden, ground or coated.
Which Cutting Gas Costs Less?
Capital plus electricity
- Compressor and storage
- Dryer and filtration
- Electric power
- Piping and pressure loss
- Filter, oil and condensate service
- Additional edge cleanup
Purity, flow and supply
- Cylinders, dewar, bulk tank or generator
- Delivery and rental
- High-pressure rated components
- Gas consumption per part
- Reduced finishing where applicable
- Supply-change downtime
Gas plus oxide handling
- Oxygen supply and delivery
- Oxygen-compatible regulation
- Fire-risk controls
- Oxide removal before downstream work
- Gas-change setup time
- Material-limited utilization
Measure accepted production
- Parts per shift
- Dross and edge quality
- Grinding minutes
- Coating or welding preparation
- Rejected parts
- Unplanned gas downtime
Compressed air often has the lowest marginal gas cost after the air system is installed. Nitrogen may still win when it eliminates enough grinding, rework or edge rejection. Oxygen may make thicker carbon-steel cutting possible but add oxide-removal labor. Compare complete parts over a representative production run.
Pressure, Flow, Purity and Air Quality
Pressure is not flow
A regulator may show the requested static pressure while the cutting head experiences a drop during high-flow cutting. Undersized tubing, long runs, restrictive fittings, saturated filters, leaks and limited compressor capacity can all reduce dynamic performance.
Use the pressure measurement point specified by the machine documentation. GWEIKE’s published MCore and M Series notes refer to pressure at the cutting head rather than simply the gas source.
Purity affects edge chemistry
Unexpected stainless discoloration may come from nitrogen contamination or pressure loss rather than laser power. GWEIKE’s M Series reference conditions specify liquid N₂ of at least 99.999% and liquid O₂ of at least 99.99%. Apply those values only where the corresponding GWEIKE table specifies them.
Compressed air must be clean and dry
Moisture, compressor oil and particles can cause unstable cutting and contaminate gas-path components. A proper system needs appropriate drying, filtration, storage, drains and maintenance. A general-purpose shop compressor is not automatically a complete laser-cutting air supply.
How to Switch Cutting Gases Correctly
Stop the process
Never change a gas supply during an active cutting job. Follow the machine and gas-system shutdown procedure.
Confirm material and thickness
Select a factory or verified parameter row for the exact alloy, thickness, machine power and cutting mode.
Load the complete gas-specific preset
Change speed, frequency, focus, stand-off, pressure, duty cycle and power exactly as the approved row requires.
Install and inspect the specified nozzle
Air/N₂ commonly use single nozzles in GWEIKE tables, while O₂ carbon-steel rows use double nozzles. Match diameter and type to the row.
Verify the approved gas system
Use compatible, rated components and the manual’s connection, leak-check and line-change procedure. Do not improvise oxygen handling.
Confirm pressure during cutting
Check the required measurement point and verify that pressure and flow remain stable under demand.
Run a representative scrap test
Inspect penetration, bottom dross, corners, small holes, edge color, striations and downstream finishing needs.
GWEIKE MCore and M Series Gas Coverage
MCore 400W fiber laser
| Material | Currently Published MCore Coverage | Important Boundary |
|---|---|---|
| Carbon steel | Air references for 1–3mm; O₂ references for 1–5mm | Use the exact gas-specific parameter guide |
| Stainless steel | Air references for 1–3mm | N₂ is positioned for cleaner edges, but no complete public MCore N₂ table is available |
| Aluminum | Air references for selected 1–2mm work | Reflective-metal protection and exact alloy testing required |
| Brass | Air references for selected thin sheet | Verify alloy and use the published material guide |
The MCore product positioning mentions approximately 4mm carbon-steel capability with the optional all-in-one air system, while the currently published factory air table covers 1–3mm. Request a verified 4mm sample instead of extrapolating the 3mm preset.
Use the MCore carbon-steel parameter guide, stainless-steel guide and aluminum/brass guide for tested starting rows.
M800 and M1200 CNC cutting mode
The M Series guide uses nitrogen for stainless, aluminum, brass and selected thin carbon steel; air for lower-cost thin sheet; and oxygen for thicker carbon steel.
See the complete M Series 800W/1200W cutting parameters and the fiber laser nozzle guide before changing gas, nozzle or focus.
Choose the gas and machine as one process
Share the alloy, thickness, monthly volume, edge requirement and downstream work to compare MCore, M800 and M1200 workflows.
Read the Fiber Laser Buying Guide Explore MCore Explore M Series Request a Gas Cutting TestFiber Laser Cutting Gas Troubleshooting
| Problem | Check First | Controlled Direction |
|---|---|---|
| Cut does not penetrate | Gas/material match and full thickness preset | Load the verified parameter group; do not adjust gas alone |
| Heavy bottom dross | Dynamic pressure, speed, focus and nozzle | Verify flow and nozzle before changing power |
| Stainless edge is yellow | N₂ purity, leaks and pressure under flow | Correct the gas supply before retuning speed |
| Air result changes over time | Water, oil, filters, compressor temperature and flow | Service air treatment and verify cutting-head pressure |
| O₂ cutting is unstable | Wrong pressure, nozzle, focus or gas row | Return to the complete thickness-specific O₂ preset |
| Dross on one side | Nozzle damage, contamination or miscentering | Inspect and center the approved nozzle |
| Aluminum protection alarm | Back reflection, focus, surface and alignment | Stop and diagnose; never disable protection |
| Result worsens after gas change | Only the gas was changed | Verify nozzle, focus, pressure, speed, frequency and power |
| Gas cost is too high | Leaks, flow, idle use and finishing requirements | Calculate cost per accepted part and compare an A/B test |
| Small holes are poor | Piercing, heat, gas and geometry | Build a separate small-feature test rather than using only straight cuts |
Assist Gas and Fiber Laser Safety
Combustion and compatibility
- Use oxygen-rated components and procedures
- Keep oil and grease away from oxygen service
- Remove nearby combustible material
- Provide appropriate fire controls
- Never leave the cut unattended
Pressure and oxygen displacement
- Secure and handle supplies correctly
- Use rated high-pressure components
- Ventilate indoor work areas
- Assess oxygen-deficiency risk
- Follow cylinder/dewar requirements
Stored energy and contamination
- Maintain the pressure vessel
- Use rated hose and fittings
- Manage condensate and oil
- Control compressor noise and heat
- Service filters and dryer
Laser and metal-fume controls
- Keep enclosures and interlocks active
- Use effective fume extraction
- Protect against reflective-metal return
- Test scrap under supervision
- Follow the machine manual and local rules
Final Recommendation
Choose compressed air for verified thin-sheet jobs where cost and simplicity outweigh a perfectly bright edge. Choose nitrogen for low-oxidation stainless, aluminum, brass and appearance-sensitive parts. Choose oxygen for thicker carbon steel where added reaction energy is required. Always load the complete gas-specific preset and compare cost per accepted part.
Compare Fiber Laser Cutters View MCore O₂ vs Air View M Series Parameters Request a Cut SampleFrequently Asked Questions
What gas is best for fiber laser cutting?
There is no single best gas. Use oxygen for thicker carbon steel, nitrogen for low-oxidation stainless/aluminum/brass edges and compressed air for verified cost-sensitive thin-sheet work.
Can a fiber laser cut with compressed air?
Yes, when the machine has a suitable clean, dry, high-flow air system and a verified air preset for the material and thickness.
Is compressed air cheaper than nitrogen?
It often has a lower marginal gas cost after the system is installed, but include compressor electricity, drying, filters, maintenance, edge cleanup and rejects.
Is air cutting oxide-free?
No. Air contains oxygen, so stainless and other edges may discolor or oxidize. Verify whether that edge is acceptable for the downstream process.
Why is nitrogen used for stainless steel?
Nitrogen ejects molten metal while limiting oxidation, which usually creates a brighter edge and can reduce post-processing when purity and pressure are adequate.
Why is oxygen used for carbon steel?
Oxygen reacts exothermically with hot carbon steel, adding cutting energy and supporting thicker-sheet penetration. It also creates an oxidized edge.
Can oxygen cut stainless steel?
It can react with stainless, but severe oxidation makes it unsuitable as the normal quality process. Use nitrogen or a verified air preset instead.
What gas should I use for aluminum?
Nitrogen is the usual quality direction. Compressed air can be used where the machine has verified thin-aluminum parameters. Reflective-metal protection remains essential.
What gas should I use for brass?
Nitrogen is the normal clean-edge direction, while verified compressed-air settings may suit selected thin brass. Test the exact alloy and monitor reflection and fumes.
Is nitrogen faster than oxygen?
Not universally. Speed depends on material, thickness and power. Oxygen has a penetration advantage on thicker carbon steel; nitrogen supports fast clean-edge cutting on sufficiently powered thin sheet.
What gas pressure does a fiber laser need?
It depends on gas, material, thickness, nozzle and machine. Use the exact factory parameter row; do not copy one platform’s pressure to another.
Is pressure measured at the regulator or cutting head?
Follow the machine documentation. GWEIKE’s referenced parameter guides specify pressure at the cutting head because supply-line pressure loss can be significant.
Why does gas purity matter?
Contamination can increase oxidation, discoloration and dross. If a proven preset suddenly fails, verify gas purity and dynamic pressure before changing laser power.
Can I change only the gas and keep the same settings?
No. Gas changes commonly require different pressure, nozzle, focus, stand-off, speed, frequency and power. Load the complete approved preset.
Does changing gas require a different nozzle?
Often. GWEIKE tables commonly use single nozzles for air/N₂ and double nozzles for oxygen-assisted carbon steel. Follow the exact row and nozzle guide.
What gas does MCore use?
Published MCore tables include compressed air for selected carbon steel, stainless, aluminum and brass, plus oxygen for 1–5mm carbon steel. Nitrogen is positioned for cleaner stainless edges, but no complete public MCore N₂ table is currently available.
What gas do M800 and M1200 use?
The CNC parameter guide includes nitrogen for stainless/aluminum/brass and thin carbon steel, air for selected thin sheet and oxygen for thicker carbon steel. These settings do not apply to handheld heads.
Should I test air, nitrogen and oxygen before production?
Test every gas that is approved for the material and machine. Compare complete presets using edge quality, dross, small features, cycle time, gas consumption and post-processing.
Choose by finished-part cost and edge requirement
Send material, thickness, edge requirement and monthly volume to build a realistic gas and machine shortlist.
Request a Fiber Cutting Test