We’ve been using laser cutting for years to precision cut all sorts of materials to a really high quality. It’s no secret that laser cutting is incredibly accurate, easy to programme using CAD and speedy too! In broad terms, the laser rapidly heats the material it is cutting causing it to either melt or vapourize.
But how does the laser do that?
What is a laser?
Laser stands for Light Amplification by Stimulated Emission of Radiation. This means that the light is concentrated into a single colour creating a monochromatic beam in which all the light waves are travelling together at the same speed with a low divergence. All this makes for a highly concentrated beam of light.
Explainthatstuff.com has created a helpful diagram to explain how the laser is created.
The diagram shows a ruby crystal with a light tube wrapped around it. At each end of the crystal there is a mirror. At one end, the mirror is partially transparent allowing the laser light to escape.
1. A high-voltage electric supply makes the tube light flash on and off.
2. With every flash, more energy is added to the ruby crystal in the form of photons.
3. The green blobs represent the atoms in the ruby that absorb the energy. When the atom absorbs this energy, one of its electrons jumps from a low energy level to a high energy level. This puts the atom into an excitable state. This state only lasts a few milliseconds because it makes the atom so unstable. The electron falls back to its original energy level and the extra energy is given off as a blue blob – scientists usually call them photons. This process is called spontaneous emission.
4. These emitted photons travel up and down the ruby crystal at the speed of light because they keep bouncing off the mirror (6) at the end of the light cylinder to the partial mirror (7) at the other end.
5. When a photon hits an already excited atom it gives off two photons instead of one. This is called stimulated emission.
8. The photons that escape form a highly concentrated beam of laser light. All the photons have the same wavelength meaning that the light appears red, like the ruby.
Bill, the Engineer Guy, explains a bit more in his video.
So How Do Lasers Cut?
The laser is directed through the laser cutting arm using mirrors to bounce the beam in the right direction. In the diagram below, the laser is focused using a special lens but it can also be focused using a curved mirror.
Compressed gas is also added to the laser cutter. The gas used may depend on the material being cut, though CO2 is often used. So with mild steel, oxygen is added to the laser to create an effect similar to an oxy-fuel torch. For materials that will just melt like stainless steel and aluminium, nitrogen is used to blow away excess material to ensure a clean finish.
The laser is centred by the nozzle to ensure the laser is pinpoint accurate. The height of the nozzle is carefully controlled to keep an accurate distance between the material and the laser. This ensures a high quality, consistent cut. The arm is controlled by a computer using CAD and moves, with the laser, to cut the material. This makes intricate designs possible as human error is eliminated from the cutting process.
When the laser is on, the laser beam focuses on a single spot less than a millimetre in diameter. Our 2 axis laser cutter has an accuracy of 0.025mm! As the laser represents around 6K Watts, this is a lot of energy to focus on one spot – especially such a small spot. This high power density causes the material being cut to heat rapidly resulting in the melting and partial or complete vaporization of the material.
To cut the material, the laser cutting arm then moves, aided by CAD, across the material. The laser’s accuracy combined with the CAD means that all sorts of intricate and complex designs are made possible with laser cutting technology that would otherwise be near impossible to achieve.
Possibly the best use of CAD is a process called Nesting. This software analyzes the different shapes due to be cut into a material and then positions them in order to minimize the amount of raw material wasted. This also eliminates human error as it takes into account which parts of the material the laser will be able to access at a time and the clamping of the material. It also recognises that some material areas may require a different quality level depending on design, particularly when using a printed pattern.
What Can You Cut with a Laser?
At Subcon Laser, we cut all sorts of materials including aluminium, stainless steel, mild steel, plastics, MDF and a whole variety of other materials. With all these materials to choose from, whatever your project, we are confident that laser cutting will help. And we even have two types of laser cutter to play with too!
Our 2 axis laser cutter is perfect for traditional flat laser cutting. We used this laser cutter to create letters for the Rust Garden in Edinburgh, a project that used mild steel in its untreated form to realise the natural decay of industry in the area. Our 5 axis laser cutter on the other hand is perfect for laser cutting 3D materials. This is particularly effective for parts used in automotive manufacturing and other more complex projects.
So there you have it.
Laser cutting is essentially the melting or vaporization of a material but on an incredibly small scale. To see what else you can do with a laser cutter, have a look at our laser cutting showcase.