Laser cutting and The Role of Nitrogen Generation

Laser cutting has many different applications in the world of industrial manufacturing. The process of laser cutting is a thermal one, and requires a steady and reliable supply of gas for the purposes of achieving a high-quality finish and maintaining a safe working environment. In this article, we will be looking at the different ways in which nitrogen supports the process of laser cutting.

How does a laser cutting machine work?

Before we look at how a laser cutting machine works, it’s important to know that there are two types of laser cutting machine that are commonly used in the manufacturing industry: fiber and CO2. The difference between how each of these operate lies in the way that the laser beam is generated and guided to the cutting head.

Fiber Laser Cutting

Light is directed through a fiber optic cable which stimulates atoms contained within, and this triggers the release of photons. The build-up of photons generates a concentrated laser beam, which then travels through the fiber optic cable, bouncing off a series of lenses within the machine’s beam delivery system until it reaches the output point where it can be focused on the metal to be cut.

CO2 Laser Cutting

 Electricity is passed through a tube filled with CO2, nitrogen, helium and other gases. Electrical energy excites the gas mixture and photons are released, which in turn generates a beam of light. This light beam produced bounces back and forth between the mirrors at each end of the laser tube and this process emphasises the intensity of the beam and makes it more concentrated. Once the beam has been generated, it works in very much a similar way to fiber laser cutting, as it travels through a beam delivery system filled with a series of lenses until it reaches the output point.

Which is the best laser cutting machine to use?

There are benefits and setbacks to each of the two types of machines. Ultimately, the decision depends on the customer’s specification from a design perspective.

For example, if someone is looking to cut across non-metal materials such as acrylic, wood or leather, CO2 is the perfect choice. CO2 lasers operate on a longer wavelength which means that the point of the beam is less concentrated and more suited for non-metal materials.

Fiber laser cutters are more powerful and better suited heavy-duty metal cutting and rigid materials as well as engraving. For example, if someone was looking at cutting components to be used in the aerospace or automotive sector, they would use a fiber laser.

While CO2 lasers offer more versatility in terms of materials they can be used on, they lack in precision due to their longer wavelength. In addition to this, fiber lasers have a much higher cutting speed especially when it comes to thin to medium-thickness metals.

Why is nitrogen needed for laser cutting?

Nitrogen’s properties as an inert gas makes it the perfect accessory to laser cutting because it means the gas will not react with molten metal, even when the laser has heated the surface to high temperatures.

Hence, nitrogen gas safely displaces the surrounding oxygen in the cutting area to prevent oxidation and undesirable effects such as rust and discolouration. The displacement of oxygen also makes for more stable gaseous composition and atmosphere around the laser cutting, which allows for the smoother finishes. This reduces the need for post-cutting treatments and helps reduce overall costs.

Another way in which nitrogen is a much-valued aid to laser cutting is that it enables the process to take place at higher speeds. The absence of oxygen reduces the risk of combustion which allows for faster cutting speeds to take place without compromising the quality of the metal.

The purpose of an assist gas

The laser beam is focused into an extremely small dot when it comes to the head of the machine that does the cutting. Due to the laser being extremely focused, the temperature increases rapidly and this poses the risk of melting the material. This is where assist gas is needed.

A nozzle- built into the cutting head- blasts the area to be cut with the assist gas. Nitrogen is the most popular choice of assist gas because of the reasons we have already covered in this article i.e., prevention of oxidation and faster cutting speeds. Another key purpose that the assist gas has, is to blow away excess molten material when the cutting is taking place to ensure neat and uninterrupted work.

Purity of nitrogen in laser cutting

The lower the purity of nitrogen gas being used, the lower the cost. That being said, the lower the purity of gas, the higher the risk of the metal decolourising. It is important for the customer to decide on the design that they want for the cutting edge before deciding on gas purity.

Whilst decolourisation is not a desirable side-effect of laser cutting, the copper and gold colour that forms as a result of oxidation can support the aesthetic of certain applications.

The message that we want everyone who reads this article to take away, is that nitrogen is very important in laser cutting for both safety and quality purposes. Having an on-site nitrogen generator not only means that you have an easily accessible supply, but it reduces the cost of needing to import nitrogen from suppliers and storing excess nitrogen, as a generator means that it can be produced in quantities as needed.

If you want to discuss your nitrogen generation needs further or want to find out more about the relationship between nitrogen and laser cutting, get in touch on our contact page and a member of the Maziak team will be happy to help you.