In laser beam cutting, the gas plays a major role in making the material to eject through the beam kerf path. Gas used in laser beam cutting is often named as &#;Assist gas&#;. Based on the application, sometimes reactive gas is used (Oxygen, O2) and sometimes non-reactive gas / inert gas is used (like Nitrogen (N2) / Argon (Ar)).

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1. Role of Assist gas

The functions of assist gas during laser cutting are as follows

To maintain the constant material removal by uniformly involving into the process

1. 1. To involve in the reaction if reactive gas is used (Exothermic reaction)
   2. To blow out the melt if inert gas is used (Fusion Cutting)

1. Purpose of Compressed Air cutting

Compressed Air is a commonly used gas in any industry. So far, air has come across wide range of applications starting from loading and lifting to cleaning and dusting. To emphasize on the part of thermal cutting, still in plasma, compressed air is used in cutting mild steel. Though we have other options like oxygen / nitrogen for laser cutting, there are still customers chose to cut with compressed air. The major reason behind that is as follows

1. 1. This is available abundantly
   2. Cost of acquiring this is very low
   3. There is already a compressed air generator available in 99% of industries
   4. There is no waiting time and no supply chain involved
   5. There is Shortage of Oxygen and Nitrogen due to Pandemic and it is the major reason for all customers switching to Air cutting from Oxygen , Nitrogen cutting

1. Properties of Air

Before we start using the Compressed Air, let us understand the basic properties of the air. Air is matter that is available in earth&#;s atmosphere. Air is a composition of Nitrogen (78%), Oxygen (21%), Argon (0.9%), Carbon dioxide (0.04%) and other gases (0.06%). This mixture also contains 1% of water vapour.

1. Air preparation for laser cutting

The air preparation is the preliminary process before using the compressed air. The preparation setup consists of following items.

1. 1. Compressor
   2. Dryer
   3. Filter
   4. Pipelines, Fittings, Valves & Pressure gauge
   5. Auto drain valve
2. Compressed Air as Assist gas

Using compressed air in the laser cutting process has a mixture of reactive and fusion cutting, as the gas contains 78% of nitrogen which is non-reactive and 21% of oxygen which is reactive. Because the portion of inert in air is high it is possible to achieve speeds equal to nitrogen cutting. As well the major portion of remaining gas is oxygen, which is a reactive gas causing more heat in the cutting.

1. Benefits of compressed air cutting

1. It provides more economical solution
2. Almost the speed of the nitrogen is achieved in air cutting
3. Maintenance cost is low
4. Post processing works are minimized for normal fabrication application
5. Dependency on third party for gas is reduced or nil

1. Limitations of compressed air cutting
   1. In case of Mild steel, there is a little dross but that is very low. The dross can be wiped. There is a black oxide layer formed on the cut surface.
   2. In case of Stainless steel, there is yellowish / blackish colour surface on the cut surface.
   3. During weld processing stainless steel after air cutting, the surface needs to be cleaned as the weld seam quality on the surface will not be proper.
   4. The major disadvantage is that the quality of air cutting depends on the laser power. The higher the laser power the speed and quality of the cutting can be improved. Also the thickness limitation is also based on the laser power.
   5. For certain application, the air cutting is undesired, as the oxidation on the surface is prolonged to react to its environment. Like aerospace, food processing, chemical tanks, vessels etc. where the surface is exposed to its environment. Because the cutting is done with air and oxidation is already on the surface, which continues to react and loses the original property of material (Corrosive resistance).
   6. It requires proper maintenance of air generation setup at periodical basis, else the optics in cutting head may fail quickly.
   7. Minimum setup or investment is required

1. Conclusion

It is one alternative way using assist gas in laser cutting process by which you gain competitive speeds in production and reduce cycle time. Thereby reducing cost of production. However, the speed and quality of cutting depends on the laser power. If the application of air cutting prevails, then it is a good alternative with proper setup.

Why Laser Air Assist Is Essential for Laser Cutting

Recently, there has been a significant increase in the number of users that are embracing air assist for laser cutting and engraving. The reason for this is not far-fetched; laser air assist systems are incredibly effective and efficient for all laser cutters and engravers, preventing burns and chars, and saving money in the long term.

What Is Laser Air Assist?

Basically, laser air assist is the act of blowing high-pressure air onto your workpiece during laser cutting or engraving. Interestingly, there are several ways to go about this; you could adopt pure nitrogen gas, oxygen gas, or pressurized air. While nitrogen and oxygen are the most commonly used assist gases; pressurized air is a cost-effective alternative to these gases. Hence, this article aims to shed more light on air-assisted laser engraving and its many advantages in your laser workshop.

What Is Laser Engraving Air Assist for?

Air assist for laser cutters helps the machine achieve better engraving or laser cutting results by minimizing heat around the laser head, dissipating heat where the laser contacts the workpiece, removing debris from around the contact point, and preventing the workpiece from burning.

How Does Laser Air Assist Work? 

Although relatively new to some, machine tool manufacturers started researching and developing the process as early as . It was found that CO2 laser engravers need more than just a light beam to successfully engrave. They also require the injection of an assist gas nozzle at the laser head to complement the operations. This convergence initiates an exothermic reaction. An exothermic reaction is a chemical reaction that releases energy through light or heat. The application of nitrogen, oxygen, or pressurized air helps transfer heat more efficiently than the beam alone. With this, you get your job done faster, cleaner, and smoother. 

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For years, oxygen was the most commonly used gas with air assist for laser engraving. It was later succeeded by nitrogen, which was found to produce a cooler engraving with cleaner edges. This was a perfect option for industries where aesthetics and edge quality were vital. However, it has been discovered that pressurized air is a more economical option with equivalent efficiency to nitrogen and oxygen.

This is not to say that pressurized air is a total replacement for nitrogen or oxygen. After all, air is made up of 80% nitrogen, with the remainder mainly consisting of oxygen. Air-assist laser cutting aims to use this high nitrogen concentration while exploiting the advantage of a much more diluted gas simultaneously.

The Benefits of Laser Air Assist

Using air assist for laser cutting and engraving has been in vogue for nearly 20 years, and has continually grown in popularity among CO2 laser cutters. Initially, mode quality was a major setback when compressed air was used for CO2 lasers, but this limitation has been minimized with time.

In these modern days, air assist has improved the capability of laser engraving some tough materials, including stainless steel and aluminum. Some of the benefits of air-assisted laser engraving include:

Profitability

Using pressurized air for an air assist comes with a substantial return on investment for businesses that utilize CO2 laser engravers. For many laser businesses, upgrading the air assist for laser cutting is the more cost-efficient way to expand laser cutting capabilities, increase the maximum cutting thickness, and achieve cleaner cuts with less char.

Cleaner Finishing

Injected air quickly dissipates the extreme heat of CO2 lasers, reducing or eliminating oxide formation &#; the cause of char or burn marks to appear on your precious laser cut products. Fighting char at its source is much more efficient than spending time on secondary clean-up operations.

Lower Production Cost

Compared to nitrogen and oxygen, pressurized air is far less costly. In some cases, the cost of using nitrogen or oxygen gas alone could make up 90% of the overall operating cost. In fact, upgrading your OMTech's laser air assist is far less costly than expected. With a fairly simple upgrade kit, you can attach a shop air compressor to create an industrial-grade air assist for laser cutting enhancements.

Improved Efficiency

Air assist can speed up your whole engraving operation. This is proven by laser engraving experiments on the complete spectrum of materials and thickness. According to a publication in The Fabricator (January ), tests have shown that nitrogen creates quicker engraving for materials thicker than ten gauge, but pressurized air is approximately 3% faster than nitrogen in the mild steel range of 0.135 inches and thinner. In addition, it is around 22% quicker for stainless steel from 0.750 to 0.036 inches, and 14% faster for aluminum in the range of 0.190 to 0.032 inches.

High Edge Quality

Although pressurized air is not the best gas for all laser cutting purposes, it does help enhance laser-cut edge quality. Air-assisted laser engraving produces an edge quality more than satisfactory for most powder coatings, woods, acrylics, and other materials.

Increased Safety

Using laser air assist also reduces the risk of debris causing a fire, as possibly combustible materials are quickly blown away from the laser beam and the excess heat it produces.

Possible Risks for Not Using an Air Assist 

When your laser engraver is running, it generates some debris as well as smoke from heat. This can be very dangerous as debris can cause flare-ups creating a fire risk. The smoke produced by heat has the following negative effects:

• Smoke can interact with the energy of the beam in the direction of your laser, decreasing the total strength and creating inconsistencies.
• A lot of smoke will create residue around the laser engraver on the laser optics and everywhere else. 
• Smoke produces discoloration, residue, and chemicals that can reach your workpiece, making it less pleasing to the eyes and your respiratory system.
• Risk of flammability depending on the materials e.g wood and certain acrylics.

Final Thoughts 

In conclusion, air assist is a crucial component for your CO2 laser engraver. It provides an effective and smooth workflow without compromising the safety of the work environment. We hope this article has exposed you to the importance of air-assisted laser engraving. OMTech has adequate provision for various types of laser engravers equipped with air assist, along with other game-changing features. Do keep us in mind and reach out to us as you commence your engraving journey.

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