28 Jan How does a Laser Cutter work?
Are you new to the world of laser cutting and wondering how the machines do what they do?
Laser technologies are very complex, and can be explained in equally complicated ways. This post aims to explain the basics of laser cutting functionality in Layman’s terms.
Unlike a household light bulb that produces bright light to travel in all directions, a laser is a stream of invisible light (usually infrared or ultraviolet) that is amplified and concentrated into a narrow straight line. This means that compared to ‘normal’ light, lasers are stronger and can travel further distances.
Laser cutting and engraving machines are named after the source of their laser (where the light is first generated), the two most common types are CO2 and Fibre Lasers. Let’s start with the most widely used, CO2.
How does a CO2 Laser work?
Modern CO2 machines usually produce the laser beam in a sealed glass tube which is filled with gas, usually carbon dioxide. A high voltage flows through the tube and reacts with the gas particles, increasing their energy, in turn producing light. A product of such strong light is heat, heat so strong it can vapourise materials that have melting points of hundreds of °C.
Mirrors and Focusing
At one end of the tube is a partially reflective mirror, the other end, a fully reflective mirror. The light is reflected back and forth, up and down the length of the tube, this increases the intensity of light as it flows through the tube.
Eventually the light becomes powerful enough to pass through the partially reflective mirror. From here, it is guided to the first mirror outside of the tube, then to a second, and finally the third. These mirrors are used to accurately deflect the laser beam in the desired directions.
The final mirror is located inside the laser head, and redirects the laser vertically through the focus lens to the working material. The focus lens refines the path of the laser, ensuring it is focused to a precise spot. The laser beam is typically focused from around 7mm diameter down to approximately 0.1mm. It is this focusing process and the resulting increase in light intensity that allows the laser to vapourise such a specific area of material to produce extremely precise results.
Moving the Laser
The CNC (Computer Numerical Control) system allows the machine to move the laser head in different directions over the work bed. By working in unison with the mirrors and lens the focused laser beam can be quickly moved around the machine bed to create different shapes without any loss in power or accuracy. The incredible speed at which the laser is able to switch on and off with every pass of the laser head allows it to engrave some incredibly intricate designs.
How does a Fibre Laser work?
Fibre technology has continually advanced in across so many industries and has been optimised so much so that light can now even be used to transport data, typically used in applications such as high speed broadband internet. If you consider fibre optic broadband compared to cable or DSL, you can instantly draw comparisons between them, one of the most apparent differences being speed.
You can begin to use this comparison to represent fibre and CO2 lasers. That’s not to say CO2 machines are something of the past, just that there is now a option of higher power and alternative laser wavelength which is ideal for engraving and cutting uncoated metals such as carbon and stainless steels, brass and copper.
Directing the Beam
The light is generated in and injected into a fibre cable and reflected through a narrow cavity that keeps the beam incredibly straight. Optics aren’t needed to direct the beam, meaning you don’t have to realign parts regularly. Due to the straightness of the laser beam, it can be concentrated to accurately focus on the most minute areas, making it perfect for laser cutting intricate designs.
Fibre engraving machines can mark uncoated metals with ease using as little as 20W of power, and at higher powers can cut through many types of metals. Instant reactions within the cable mean a fibre laser is ready to work as soon as it is switched on.
If you have any questions about this topic, please get in touch!
For information about laser markers and engravers see What is Laser Marking?