What is Laser Cutting?
Laser cutting is a manufacturing technique that uses a high-power laser beam, directed through optics and computer numerical control (CNC) to create a high-quality and dimensionally accurate design on sheet metal.
Laser cutting is a form of non-contact fabrication. It uses a small laser to burn, melt, or vaporise a design alongside a jet of gas, leaving a high-quality surface edge. Electrical discharges combined with the stimulation of the lasing materials, create the laser beam which is then guided by the motion control system that follows the CNC pattern.
What Are Laser Assist Gases?
The assist gas plays a crucial role in laser cutting by removing molten material and preventing it from solidifying on the surface. It also helps cool the material, reducing the risk of warping or distortion. Commonly used assist gases include nitrogen, oxygen, and compressed air.
Selecting the Right Laser Assist Gas
The role of assist gas is used to facilitate the laser cutting process, removing the melted substance from the component which results in a neat and precise cut. While each project has its own set of requirements and applications, selecting the right laser cutting gas is essential as it can impact cutting speed for certain materials as well as the edge quality.
Nitrogen and oxygen are the most commonly used assist gases in laser cutting. Both gases can create a different set of results due to their unique properties. Oxygen is reactive and Nitrogen is not reactive which can impact the following areas within the laser-cutting process:
- Cutting speed
- Edge quality
- Suitability for different materials
- Cost
Ultimately, the right assist gas can accelerate cutting speeds for certain materials and improve the edge quality.
How do Nitrogen and Oxygen Compare?
Oxygen (O₂)
Oxygen is a good choice for laser cutting mild steel as it speeds up the cutting process. Unlike Nitrogen, Oxygen is reactive with heated metal therefore the exothermic reaction can significantly increase the cutting temperature, resulting in faster cutting speeds. Oxygen cutting is also effective when used on thicker materials, providing a cost-effective solution that uses less pressure.
While there are some advantages to using oxygen as a laser-cutting gas, there are also some drawbacks to consider. Using oxygen in the laser cutting process can produce an inferior edge quality in comparison to using Nitrogen. This is because Oxygen cutting oxidizes the edges of cut steel, and when such edges are intolerable, oxygen is not viable as a gas choice.
The oxidised surface may also affect the powder coat resulting in extra costs for finishing methods like descaling or deburring (if required). We provide alternative methods of descaling such as manual deburring or barrelling which is well suited to high-volume batch production.
Nitrogen (N₂)
Providing the best edge quality, Nitrogen is an excellent choice for laser cutting. Its inert nature means it will not react with any of the components of metal during the cutting process and it is also a non-contact.
We use Nitrogen to cut mild steel although the speed benefits are not realised as the nitrogen does not assist laser cutting in the same way as oxygen does. However, laser cutting with nitrogen has one major benefit when compared to cutting with oxygen as it prevents an oxidised edge on the part. Whilst this looks aesthetically pleasing it also means that the parts can be painted without a descaling operation.
Some more benefits include:
- Lower cost
- High-cutting speed for thin materials
- High productivity
- Better control
- Suited to a wide range of materials
Summary Table
Feature | Nitrogen (N₂) | Oxygen (O₂) |
Reaction with Material | Non-reactive
|
Oxidation (exothermic reaction) |
Cut Edge Quality | Clean, oxide-free | Oxidized, may require cleaning |
Cutting Speed | Slower for thick materials | Faster, especially for thick materials |
Material Compatibility | Best for stainless steel, aluminium | Best for carbon steel |
Cost | Higher gas and energy cost | Lower gas cost, higher speed |
Post-Processing | Minimal or none | Often required |
Heat-Affected Zone | Narrow | Wider |
Other Laser Assist Gases
Compressed air
Compressed air is a cost-effective assist gas commonly used for cutting thin sheets of materials like aluminium, stainless steel, mild steel, and galvanised mild steel. It combines nitrogen and oxygen naturally present in the air, offering a balance of speed and quality. While it can leave minor oxidation on edges, its low cost and versatility make it suitable for less critical applications.
Argon
Argon is a noble gas that is ideal for cutting and welding applications where edge quality and minimal oxidation are paramount. It is particularly effective for reactive materials like titanium and aluminium, as it provides a completely inert environment. However, its high cost limits its use to specialised applications where superior quality is required.
Carbon dioxide
Carbon Dioxide (CO₂) is less commonly used as an assist gas but is occasionally employed for cooling and shielding during laser processing. Its primary role is to stabilise the cutting area by minimising thermal effects, though it is more frequently associated with CO₂ lasers as a source rather than an assist medium. Its use is typically application-specific.
Our Nitrogen Supply
We offer Nitrogen laser cutting for customers and with our 30,000-litre tank, we can supply our fibre laser cutting machines with high-quality nitrogen.
The tank is filled up regularly by our supply partners Air Products who monitor the levels remotely using advanced telemetry systems. This ensures that we do not run out of gas.
Contact Us
Our team of estimators can advise what type of gas is required for different projects depending on customer requirements. Contact us today with your specifications, and we’ll get back to you within 24 hours.