How do CO2 laser cutters work?
If you are getting started in the world of laser cutting and engraving, you may be considering purchasing a CO2 laser cutter. This article explains how CO2 laser cutters actually work in simple terms that are easy to understand.
For more practical considerations on how to get started with a budget CO2 laser cutter, check out our beginner’s guide to the K40 laser cutter.
What are CO2 laser cutters/engravers?
CO2 laser cutters are probably the most popular type of laser engraver used by hobbyists and small businesses (the other popular type being diode lasers). In recent years the cost of laser engraving equipment has fallen dramatically, allowing more people than ever to get involved in this interesting and productive hobby.
Laser cutters and engravers can be used to produce custom-made and engraved items from a variety of different materials, including:
- Paper
- Cardboard
- Wood
- MDF
- Plastic
- Acrylic
- Cork
- Rubber
Note that CO2 lasers cannot cut metal – fibre lasers are used for cutting and engraving metals.
How is the laser beam produced?
The term “Laser” stands for Light amplification by stimulated emission of radiation. But what does this actually mean?
The laser beam in a CO2 laser cutter originates in a CO2 (carbon dioxide) gas-filled glass tube, with a mirror at one end and a partially reflective mirror at the other. As electricity is passed through the tube, the CO2 particles absorb energy which causes them to emit light. This light is reflected between the two mirrors until it has enough energy to pass through the partial mirror at one end of the tube.
The laser beam contains enough energy focused on such a small point that it is able to vaporise material (turn material from a solid directly to a gas). This vaporised material, which we see as smoke/fume, is then sucked out of the laser enclosure by a fan.
The laser beam itself is infrared light, meaning that it is not visible to the human eye. It is very important to only run the laser inside an enclosed housing and to wear eye protection. As the beam is invisible you wouldn’t know it was going to hit you until it was too late!
How is the laser beam controlled?
The CO2 tube within the laser cutter is in a fixed position. Once the beam exits the tube it is directed by a set of movable mirrors. The mirrors are mounted on a gantry and are moved by motors which are in turn controlled by a computer. It is important that these mirrors are kept clean and in good condition to minimise any potential lack of reflection which will effectively reduce the laser’s power.
Directional Mirrors
The beam is reflected to the desired location and into the laser head. Within the laser head is a mirror which directs the beam vertically and a focusing lens that focuses the light into a laser beam which is able to cut through the material.
Focus Lens
The focus lens helps to concentrate the beam even further and increase its effective power. The effective working area is concentrated over a very narrow band:
When cutting it is very important that the middle of your workpiece is directly at the point in which the laser beam is focused. Having your workpiece higher or lower than the focus area will result in the light being spread over a greater area, resulting in less cutting power and unclean cuts.
Power variation
CO2 laser cutters have the ability to operate with varying levels of power. This means that it is possible to cut the materials completely or only partially cut through and leave a mark on them. This is known as engraving.
To depth to which a CO2 laser can cut depends on its maximum power (assuming the machine has been set up correctly). The power of a CO2 laser is expressed in Watts, with a higher Watt value corresponding to a more powerful laser that can cut through thicker materials or cut thinner materials faster. Entry-level CO2 laser cutters are usually 40W, however, industrial-level machines can be 500W or even higher!
The laser beam can be turned on and off extremely quickly. When combined with the movable position, this allows CO2 lasers to create extremely intricate engravings.
CO2 laser cutter software
Most CO2 laser cutters are controlled by integration with a computer utilising special software.
Firstly you create a design that you want to cut or engrave in a program such as Inkscape. This is then fed into specialist software such as Lightburn which interprets the data and sends it to the laser cutter. The laser cutter then follows the set of commands and completes the cutting/engraving.
What are some advantages of using a CO2 laser cutter?
CO2 laser cutters offer many advantages over conventional processes such as cutting with a saw.
- Low power consumption (check out How much does it cost to run a K40? for a full cost analysis)
- Much quieter than conventional cutting
- Safer than using conventional cutting as there are no sharp blades or exposed moving parts
- Precise and repeatable cuts and engravings – just load in your material and start the machine
- Large variety of applications – you can make many different things on a wide range of materials
- Low cost of entry into laser cutting – K40 laser engravers can be bought for under $500
What are some disadvantages of using a CO2 laser cutter?
There are a few drawbacks of using a CO2 laser cutter:
- Fume generation – as the workpiece material is being vaporised this can create a lot of excess fume and smoke – this must be vented away using a fume extraction system. There is the potential to vaporise hazardous materials such as PVC, which will create chlorine gas! Take care to ensure that any working materials are laser safe. If in doubt check your supplier’s Material Safety Data Sheet (MSDS).
- Fire risk – CO2 laser cutters work by burning through material so it is no surprise that they are a potential fire risk. Never leave a laser cutter running unnattended!
- Limited on the thickness of material – the thicker the material you are trying to cut, the more powerful a laser you will require. Entry-level CO2 laser cutters will struggle to cut through material thicker than 10mm.
- Require precise set-up and regular calibration – the mirrors within the CO2 laser cutter must be nearly perfectly aligned to ensure maximum effective power. This can be quite challenging for the inexperienced.
How do CO2 laser cutters work? Conclusion
CO2 laser cutters are not a new technology however their recent reduction in price has made them more affordable and accessible to a wider audience.
Hopefully, you now have a deeper understanding of how a CO2 laser cutter actually works.