Fiber laser cutting machines have revolutionized the metalworking industry with their precision, speed, and versatility. However, to achieve optimal performance, the correct assist gas needs to be selected. This article will guide you through the factors to consider when selecting the correct gas for your fiber laser cutting machine.
 

Assist gases influence the quality of the cut, cutting speed, and the overall efficiency of the process. The primary functions of assist gases include:

Ejecting Molten Material: Assist gases help remove molten material from the kerf, preventing re-solidification and ensuring a clean cut.

Cooling the Workpiece: The gas cools the workpiece and minimizes heat-affected zones.

Protecting the Lens: Assist gases can shield the lens from splatter and debris, maintaining the integrity of the laser optics.

Enhancing Cutting Speed and Quality: Different gases interact with the material in various ways, affecting the cutting speed and the quality of the edges.
 

The most commonly used assist gases in fiber laser cutting are oxygen (O₂), nitrogen (N₂), and compressed air. Each gas has unique properties and applications.

Oxygen (O₂): Oxygen supports an exothermic reaction with iron, increasing the cutting speed and facilitating the cutting of thicker materials, typically used for cutting mild steel. It can increase cutting speed on mild steel and provide better edge quality on thicker materials. However, be aware that oxidized edges may require additional cleaning or treatment and there is a higher risk of burning. On thin materials, a rough surface may result.

Nitrogen (N₂): Nitrogen acts as an inert gas, preventing oxidation and producing a clean, shiny cut edge, it is used for cutting stainless steel, aluminum, and other non-ferrous metals. Nitrogen cutting produces no oxidation, a high quality edge finish and is suitable for thin and reflective materials. Its disadvantages are higher cost compared to oxygen and slightly slower cutting speeds for thicker materials.

Compressed Air: Compressed air combines the properties of both nitrogen and oxygen, providing a balance between cost and performance, and is suitable for cutting thin metal materials. Compressed air has lower operating costs and can provide suitable cutting speeds and edge quality for some applications, but in ferrous materials, there is a risk of oxidation and it is less effective on thick materials.
 

Material Type: For mild steel, oxygen is preferred because it increases cutting speed through an exothermic reaction. For stainless steel and aluminum, nitrogen is ideal to avoid oxidation and achieve a clean edge. For thin metal materials, compressed air is an economical choice.

Material Thickness: For thicker materials, oxygen can significantly increase the cutting speed. For thin materials, nitrogen provides superior edge quality without the risk of burning.

Cutting Speed and Quality Requirements: If high cutting speed is the priority, oxygen is the preferred choice for mild steel. For applications requiring high edge quality, especially in stainless steel and aluminum, nitrogen is the best option. Compressed air offers a balance for less critical applications where cost is a major factor.

Cost Considerations: Oxygen is relatively low cost but may require post-processing to clean oxidized edges. Nitrogen is more expensive due to purity requirements but reduces the need for post-processing. Compressed air is the cheapest option but may compromise edge quality and oxidation control.

Environmental and Safety Concerns: Ensure proper ventilation and safety measures when using oxygen, as it supports combustion. Nitrogen is inert and poses fewer risks but requires careful handling to avoid asphyxiation. Compressed air systems need to be free from contaminants that could affect the cut quality and machine performance.

 

Choosing the correct assist gas for your fiber laser cutting machine is beneficial for optimizing performance, quality, and cost-effectiveness. By understanding the properties and applications of oxygen, nitrogen, and compressed air, and considering factors such as material type, thickness, and cutting requirements, you can make informed decisions that enhance your cutting operations. Regular experimentation and system maintenance will further ensure that you achieve the best possible results with your laser cutting machine.