This guide explains assist gas selection, supply methods, pressure requirements, and gas switching on the Thunder AccuMetal 24 to help achieve consistent cutting quality and efficient operation.

1. The Role of Assist Gas

Assist gas is one of the three core elements of laser metal cutting, alongside the laser source and optical system. It is delivered through a nozzle positioned a few millimetres above the workpiece and serves three primary functions:

· Removal of molten metal. The high-velocity gas stream ejects molten material from the bottom of the kerf, preventing it from re-solidifying along the cut edges.

· Cooling and lens protection. The gas forms a concentric barrier around the laser beam, shielding the focusing lens from spatter and fumes while cooling the cutting zone and minimizing the heat-affected zone (HAZ).

· Chemical assistance (oxygen only). Oxygen undergoes an exothermic reaction with iron in carbon steel, releasing additional heat that can increase cutting speed by 40–50%.

2. Selection of Assist Gases

Table 1. Comparison of the Three Common Assist Gases

3. Methods of Gas Supply

Table 2. Four Common Methods of Supplying Assist Gas

Method	Image	Gas & Purity	What You Need	Advantages	Disadvantages	Best For
High-pressure cylinders		O₂ ≥ 99.5%, N₂ ≥99.99%	40L cylinders with a pressure regulator	Low initial investment; flexible gas switching	Limited gas volume per cylinder, frequent replacement, pressure fluctuation as cylinder pressure drops, and the highest unit cost under heavy consumption	Small batches, prototyping, intermittent production
Liquid nitrogen tank		N₂ up to 99.999%	Liquid nitrogen tank, ambient-air vaporizer, and pressure regulator	High purity, stable delivery pressure, and a unit gas cost approximately half that of cylinders	Requires space and foundation works; evaporation loss, periodic refilling, and cryogenic handling risks	Thick stainless steel/ aluminum, medium-to-high nitrogen use
Nitrogen generator		N₂  99.5%–99.999%, adjustable	Nitrogen generator, buffer tank, and booster compressor	Lowest long-term  operating cost; no waiting for delivery and no cylinder rental	High initial investment; requires electricity and compressed air, and a booster is necessary to reach cutting pressure	Continuous shifts, high nitrogen consumption
Air compressor		Compressed air; dew point and oil ≤ 0.01 mg/m³	Air compressor, air tank, dryer, and precision filter	Only electricity  is consumed; the lowest running cost	Provides compressed air only; oil or water ingress in the supply line may contaminate the focusing lens	Bright edges on thin/ medium carbon steel and aluminum; parts tolerant of oxidation color

4. Gas Pressure Requirements

When compressed air is used as the assist gas, the following pressure settings are recommended: (1 MPa ≈ 10 bar). 

Table 3. Recommended Cutting Thickness and Minimum Compressed-Air Pressure

5. Switching Gases on the THUNDER ACCUMETAL 24

The THUNDER ACCUMETAL 24 is equipped with two independent gas channels, allowing nitrogen and oxygen to be connected simultaneously. Once the gas supply is connected, the operator can switch between gases directly in the NcStudio software, as shown in the figure below.

If compressed air is required, note that the oxygen channel is fitted with a dedicated flashback arrester. Therefore, compressed air may be connected only to the nitrogen channel—never to the oxygen channel. Once connected, gas switching is still carried out in the NcStudio software. When using argon, follow the same procedure as for compressed air.

6. Summary

· Oxygen (O₂) participates in the cutting reaction, acting both as the driving force for dross removal and as the combustion reactant. It is best suited to carbon steel and low-alloy steel.

· Nitrogen (N₂) provides inert shielding and removes dross purely through gas flow, without participating in chemical reactions. It is best suited to stainless steel, aluminum alloy, and brass.

· Compressed air is a mixture of approximately 78% N₂ and 21% O₂, combining the characteristics of both gases at the lowest cost. It is best suited to carbon steel, stainless steel, aluminum, and copper.

It should also be noted that compressed gas drives auxiliary machine accessories, such as the material clamping device. Ensure that the gas supply is sufficient before production begins.

Please check out the link below for more details:

Pneumatic Clamp Operation and Gas Supply System Overview