Maximize Efficiency: Air as Auxiliary Gas in Laser Cutting

Laser cutting is a technology that has been widely adopted in various industries since its inception in the 1960s. The use of lasers in cutting has revolutionized the production process and has made it possible to cut materials with great precision and efficiency.

However, with the increasing popularity of laser cutting, the price competition between enterprises has become more intense, leading to a decrease in profitability for laser cutting equipment.

In order to reduce the cost of laser cutting equipment, it is necessary for enterprises to focus on improving their production processes and increasing efficiency.

One effective way to do this is by utilizing air as an auxiliary gas in the laser cutting process. Using air as an auxiliary gas can reduce the cost of cutting by reducing the consumption of expensive gases such as nitrogen or oxygen.

Additionally, air is readily available and does not require any special storage or handling, making it a cost-effective alternative.

In conclusion, using air as an auxiliary gas in laser cutting can help enterprises reduce their cutting costs, improve efficiency, and enhance their competitiveness in the market.

This strategy can be implemented as part of a larger effort to transform and upgrade the production process, and to focus on more value-added activities such as process improvement, efficiency improvement, and R&D investment.

The influence of different auxiliary gas on cutting quality

First, let’s examine the process of laser cutting:

The laser generated by the laser generator is focused through a lens and converges to form a small, intense light spot. The distance between the lens and the plate is carefully controlled to ensure the stability of the laser spot in the direction of the material’s thickness.

At this point, the lens focuses the light into a spot with a high power density, typically reaching 106-109W/cm2. The material absorbs the energy from the light spot, causing it to instantly melt, and the molten material is then removed by a stream of auxiliary gas, completing the cutting process.

Throughout the entire cutting process, the auxiliary gas serves two main purposes: to provide the necessary force for cutting and to remove the molten material from the workpiece.

In this process, different types of gases have different effects on materials and sections:

(1) Oxygen

When oxygen is used as the auxiliary gas, it not only removes the molten metal but also triggers an oxidation reaction that enhances the melting of the metal, allowing for the processing of thicker materials. This significantly improves the laser’s processing power.

However, the presence of oxygen also leads to significant oxidation on the cutting surface of the material. Additionally, the oxygen has a quenching effect on the material surrounding the cutting surface, which improves its hardness and has positive impacts on subsequent processing.

(2) Nitrogen

As an auxiliary gas, nitrogen creates a protective atmosphere around the molten metal, preventing oxidation and preserving the quality of the cut surface. However, nitrogen does not have an oxidation capacity to enhance heat transfer like oxygen, so it doesn’t improve the cutting ability.

Additionally, using nitrogen as the auxiliary gas leads to high consumption, resulting in increased cutting costs compared to other gases.

(3) Air

Air, which is composed of 78% nitrogen and 21% oxygen, can be used as the auxiliary gas in laser cutting. However, the presence of oxygen in the air will result in oxidation at the cutting section, but the large amount of nitrogen in the air will prevent excessive oxidation and enhance heat transfer.

Therefore, the effect of cutting with air is intermediate between cutting with nitrogen and cutting with oxygen. The benefit of cutting with air is its low cost, which is primarily due to the power consumption of the air compressor and the cost of filter elements in the air pipeline.

The effect of different auxiliary gas on cutting cost

FIG. 1 illustrates the cutting section effect of 1.5mm thick 304 stainless steel using nitrogen and air as the auxiliary gas. As seen in the figure, when nitrogen is used as the auxiliary gas, the section is shiny and bright, while when air is used, the section is pale yellow.

A comparison of the cutting costs of air and nitrogen as auxiliary gases for 1.5mm thick 304 stainless steel is presented in Table 1. The comparison uses the latest generation of fiber laser cutting machines equipped with self-developed fiber laser generators.

The cost analysis reveals that using air as the auxiliary gas results in a 23.7% decrease in cutting costs per hour compared to using nitrogen. This reduction in cutting costs can have a significant impact in reducing the overall processing costs for the factory.

Furthermore, the power consumption of the air compressor is analyzed as follows:

Many enterprises currently use non-variable screw air compressors. If a permanent magnet frequency screw air compressor is used, it can result in a savings of up to 50% in electricity for the air compressor alone.

When air is used as the auxiliary gas, the cutting cost is 36.2% lower than when using nitrogen.

Table 1 Cutting cost comparison

Note:

(1) The cost analysis mentioned above was calculated with the following assumptions:

• The operation ratio of the machine tool was assumed to be 70%.
• The electric charge was assumed to be 1 yuan/KW.
• The cost of nitrogen was calculated based on the price of liquid nitrogen at 1.5 yuan/kg.

(2) The power consumption of the air compressor when cutting with air was calculated for a non-variable screw air compressor with a capacity of 17.5kW, pressure of 1.26MPa, and flow rate of 2.3m³/min.

(3) When nitrogen is used as the auxiliary gas for cutting, the air compressor still needs to supply gas to the machine, which results in electricity costs.

(a) The cutting section when nitrogen as the auxiliary gas

(b) The cutting section when air as the auxiliary gas

(c) Section comparison of two parts (nitrogen on the left and air on the right)

Fig.1 Cutting section effect when using nitrogen and air as the auxiliary gas

The range of application when using air as the auxiliary gas

(1) Carbon steel plate /Q235 steel plate

When the plate thickness exceeds 1.5mm, a certain amount of burr will be generated on the cutting section. However, the burrs are not sharp enough to scratch paper.

The maximum thickness that can be cut with air as the auxiliary gas varies depending on the power and type of laser generator.

(2) Stainless steel plate /SUS304 steel plate

The cutting section produces a yellow oxide layer.

(3) Aluminum plate /A1050 plate & Aluminum alloy plate /A5052 plate

The cutting burr will be reduced compared to using nitrogen as the auxiliary gas.

Table 2 displays the cutting range when air is used as the auxiliary gas for both carbon dioxide laser cutting machines and fiber laser cutting machines.

Table 2 The maximum thickness of the plate is cut when the air is used as an auxiliary gas

The effect of air as an auxiliary gas on cutting

(1) For carbon steel plate

When air is used as the auxiliary gas during cutting, the cut sections will produce smaller burrs, but these burrs are not sharp and can be acceptable for parts with low burr requirements.

(2) For stainless steel plate

When air is used as the auxiliary gas during cutting, the material will undergo oxidation, leading to defects such as slag and stoma in the welding section, which will negatively impact the quality of the welding seam and decrease the strength of the welding joint.

Therefore, it’s necessary to remove the oxide layer from the welding section by polishing to improve the welding quality after cutting with air as the auxiliary gas.

Additionally, the cut section will develop a yellow oxide layer, which can be problematic for outer parts. This oxide layer also affects the welding process, and it’s necessary to polish it before welding can be performed.

(3) For aluminum plate and aluminum alloy plate

Using air as the auxiliary gas can reduce the size of the cutting burr, while using nitrogen will result in larger cutting burrs.

Requirements for air supply device when using air as the auxiliary gas

When air is used as the auxiliary gas, a pressure of 0.9MPa is required. To meet this requirement, it’s recommended to use a screw-type air compressor with a rated working pressure of 1.26MPa and a flow rate of 2.3m3/min.

It’s important to ensure the quality of the compressed air, with a drying rate of 99% and moisture content less than 1/100. To achieve this, it’s necessary to use high-quality filter elements in the compressed air pipeline and replace them regularly.

For choosing a dryer, two options are available: a regenerative adsorption dryer and a freeze dryer. While both have their own characteristics, it’s recommended to choose the regenerative adsorption dryer for its stability, ease of maintenance, and long-term use.

When selecting the diameter of the compressed air pipeline and pressure reducer, it’s important to consider the flow and pressure output of the compressor to maintain stable pressure when using compressed air.

It’s worth noting that permanent magnetic frequency converter screw air compressors are available in the market, which can save up to 50% electricity compared to non-variable speed screw air compressors.

Conclusion

In today’s highly competitive industrial environment, companies can gain a competitive edge by improving their production processes, enhancing the design level of their products, and other means.

Another effective way to achieve a competitive advantage is by reducing processing costs within the existing process.

By using air as the auxiliary gas for cutting materials, companies can reduce cutting costs and increase profits, providing support for their transformation and upgrading efforts.