What is CO2 Laser Cutting, and How Does it Work?

When it comes to cutting parts from a sheet, the precision and speed of a laser cutter are hard to beat. However, not all laser cutters and engravers are the same or offer the same capabilities.

One of the most popular types is the CO2 laser cutter. Hobbyists can purchase or build small CO2 laser cutters for tasks like engraving wood and leather, cutting paper, and working with certain plastics. On the other hand, product designers needing to cut metal sheets or thicker wood and plastic must rely on more powerful industrial laser cutters.

This article delves into what a CO2 laser cutter is and how it operates. Keep reading to discover what sets these CNC laser cutters apart.

What is CO2 Laser Cutting?  

A CO2 laser cutting machine, also known as a carbon dioxide laser, uses high-intensity light to vaporize material from a workpiece with remarkable precision. The laser head is controlled by a computer (CNC) to cut shapes from sheets of material, as well as create slots and bore holes with high accuracy to meet design specifications.

What sets a CO2 laser cutter apart from other CNC laser cutters is how the laser beam is generated and directed. It produces high-intensity infrared light by using electricity to excite a gas mixture containing carbon dioxide. The continuous infrared laser beam is then focused and guided to the workpiece through a series of mirrors and lenses.

How Does a CO2 Laser Cutter Work?  

The beam generation in a CO2 laser takes place inside an airtight glass discharge tube filled with a gas mixture, with mirrors at both ends. A high electrical voltage is applied to excite the gas molecules, causing them to emit light.

The gas mixture must include nitrogen and helium, but carbon dioxide molecules are responsible for emitting the light. The infrared light produced by the CO2 laser has a wavelength that transmits efficiently through the atmosphere, allowing it to maintain intensity over longer distances.

The mirrors at either end of the discharge tube play a crucial role: one mirror is fully reflective, while the other is partially reflective. These mirrors work together to amplify and direct the light into a beam that passes through the partially reflective mirror.

Once the beam exits the discharge tube, it is guided by a series of mirrors and lenses to the laser head, where it is focused into a narrow, high-intensity beam aimed at the workpiece.

In addition to the beam generation and transmission, CO2 laser cutters rely on computer numerical control (CNC) to precisely position and move the laser, ensuring accurate cuts—even for intricate or delicate features.

CO2 Laser Cutter Benefits & Limitations  

Benefits:  

CO2 laser cutting offers several advantages compared to other cutting methods:

- High precision and small kerf width, allowing for excellent detail on fine features.

- Efficient operation, often using less power than other processes.

- High production speed, particularly for cutting thinner materials (though not as fast as fiber lasers).

- Minimal debris and easy cleanup, as the process produces little waste, primarily in the form of dust.

- Superior edge quality and surface finish, better than that achieved by waterjet or plasma cutting.

- Non-contact cutting, which avoids introducing impurities into the material, making it ideal for medical applications.

Limitations:  

However, product designers should consider the following limitations of CO2 laser cutting:

- Limited cutting thickness for metals—thicker metals are better suited for waterjet cutting or electrical discharge machining.

- Not suitable for highly reflective materials, as these can reflect the laser beam, reducing effectiveness.

- Beam misalignment sensitivity, which requires skilled technicians to properly adjust mirrors and focus lenses.

- Heat-affected zone (HAZ)—the high heat input can alter the mechanical properties of the material around the cut area.

- Toxic gases can be released when cutting certain plastics and organic materials, such as polyvinyl chloride (PVC), which requires proper ventilation or avoidance of those materials.