Laser cutting has grown tremendously in popularity over the past few decades. As such, it is a hugely versatile technology that seems almost limitless. Lasers cut the silicones in microchips, are used for eye surgery and cut fururistic materials for space travel, just to show how wide the scope can be.
Yet there is still a lot that people don’t know about laser cutting. In this article, we’ll bring you up to speed on the basics.
Table of Contents
- What is laser cutting?
- What happens to the material during laser cutting?
- Benefits of laser cutting
- Can all materials be laser cut?
What is laser cutting?
LASER stands for “Light Amplification by Stimulated Emission of Radiation.” There are different methods of creating a laser, but the essence is always the same. A light source is used to create a stream of photons. This stream is amplified by reflection and lens effects to create a focused laser beam. A parallel beam is emitted. This beam of light is used to melt, burn, or vaporize materials, and this offers several applications for machining meterials.
You have also experienced this effect in everyday life. Think of starting a fire with a magnifying glass. A beam of light is gathered by the magnifying glass into one point. There it has a very high intensity. A laser works on the same principle. This allows it to cut through different materials.
What happens to the material during laser cutting?
There are several ways that a laser can make a cut. It all depends on the material cut and the settings of the laser cutting machine.
The word evaporate is popularly used mainly when a liquid changes to a gas. A material melts and then evaporates. In laser cutting, however, evaporation refers to skipping the liquid phase. Thus, the material goes from solid form directly to a gas form.
When the material absorbs the energy made by contact with the laser source, there is no time to melt first. A cut is made first. On the cutting surface, the absorption is so great that the material evaporates even faster, and that erodes the cutting edge even faster while material is being disposed of in gas form.
Evaporation is especially applicable when we are cutting plastics wood, paper or textiles because a low amount of energy quickly causes the material to phase transition.
In materials melting, on the other hand, the liquid phase of the material is not going to be skipped. We are going to change solid material into a liquid and thus employ a cutting process. Melting requires significantly less energy. Up to ten times less laser power is required to melt a workpiece than to vaporize it. Thus, melting is well suited for low-power laser cutters.
The molten material is then removed by blowing it away with a gas jet from the cut. Various gases are used for this purpose. They are all non-reactive such as helium, argon or nitrogen.
Because of its low intensity, it is especially suitable for non-oxidizing materials such as stainless steel, aluminum, titanium and various metals and metal alloys.
Reactive laser cutting
Zoals hierboven vermeld, wordt bij het smelten het gesmolten materiaal verwijderd door een gasstraal van een niet-reactief gas. Er zijn echter ook procédés waarbij een reactief gas wordt gebruikt om het snijproces te ondersteunen.
Eerst zal een laserstraal het materiaal smelten. Wanneer het materiaal gesmolten is, wordt een reactief gas in de snede geblazen (meestal zuurstof). Het materiaal reageert dan met dit gas. Er ontstaat een exotherme reactie, wat betekent dat er nog meer warmte vrijkomt. Dit bevordert het verdere smelten. Het is zeer geschikt en wordt vooral gebruikt voor het snijden van metalen.
Metaal vereist over het algemeen een hoog vermogen om te snijden. In dit geval wordt echter 60% van de totale snij-energie geproduceerd door de reactie tussen het metaal en het reactieve gas. Een serieuze besparing. En bovendien wordt, net als bij het normale smeltproces, het gesmolten metaal gelijktijdig van de snede weggeblazen.
Er is nog een bijkomend voordeel aan deze techniek. Niet alleen kan men meer doen met lasersnijmachines met een lager vermogen, maar de snijsnelheid ligt ook beduidend hoger. Het nadeel is echter dat het proces gebaseerd is op een chemische reactie. Dit in combinatie met de hogere snijsnelheid vermindert de snijkwaliteit aanzienlijk in vergelijking met het gebruik van een niet-reactief gas.
Reactief lasersnijden wordt voornamelijk gebruikt voor het snijden van staalsoorten die rijk zijn aan koolstof of titanium en andere metalen die gemakkelijk oxideren.
Thermal stress fracture
In a thermal stress fracture, the laser cutting machine is used to heat up the material to create local internal stresses. After the laser passes, the material cools back down and this creates internal stresses in the material. In some machines, coolants are used to further control these stresses.
When these internal stresses are large enough, a crack appears and separates the material at that location. The movement of the laser beam controls this cut.
This method uses substantially less power than evaporation or melting at a higher cutting speed. It is mainly used when cutting glass or ceramics.
Benefits of laser cutting
The laser beam is digitally controlled by a Computer numerical control (CNC) controller. This makes the process very suitable for cutting complex shapes since the controller can follow any pattern without having to set it manually. The desired shape is thus drawn in a software package. The laser automatically follows this pattern. This is a great advantage over, for example, the more traditional forms of processing such as turning or milling. There, the path of the machine must often still be set manually (although there are also emerging CNC applications).
With the laser cutting machine, the workpieces being cut do not move. Thus, in general, there is no need to clamp the material. The amount of material removed is also relatively small. A laser cuts across a relatively thin line. Compared to sawing, turning or milling, a laser cutter also has an advantage here.
Laser cutting also involves no internal stress on the material, which allows the machines to cut fragile or brittle material. No post-processing is required in most cases either.
The machine does not come into contact with the material itself. So there is also no wear and tear on the cutting tools as in other applications that have many fragile parts.
Cutting different materials makes the laser cutting machine very versatile. Cutting metals with different thicknesses to plastics to textiles are all possible. Laser engraving or burning is also possible. It all depends on the settings of your laser machine. Again, a laser system has an advantage against more traditional cutting techniques, where for different materials, different cutting tools have to be installed.
In other words, the technology is very versatile, goes fast, is inexpensive and low-maintenance.
Can all materials be laser cut?
Not all materials are best cut with a laser cutter. Most materials are safe, but there is always a chance that gases are released that are not healthy when the material is heated. Especially with non-metallic materials, you need to be extra careful.
Other materials do not produce good results when cut by a laser cutting machine. Below is a general list of what is suitable and what is not.
Materials you can laser cut
Laser cutting works on a wide range of materials both metal and non-metal workpieces. Below is a general list to give you a good idea of what is possible.
Laser cutters can cut all kinds of metals, from stainless steel to aluminum to all kinds of alloys. It is mainly made for sheet steel and other metal plates and tubes. Thin sheets are very popular, but thicker sheet metal can also be machined.
Aluminum and other highly reflective metals are more difficult to cut, in those cases the fiber laser is mainly resorted to.
The thickness of metals is very dependent on the material type and on the type and power of your laser cutting machine. The expertise of the user is also a factor.
Wood is well suited for laser cutting. Often wood is treated with a laser cutter to make assembly items, or for engraving. The thinner the wood, the easier the cutting process.
Be wary of oils or resins. Not only do these evaporate, they also increase the risk of your workpiece catching fire.
Paper and cardboard
Paper and cardboard can also be laser cut, which is how those intricate shapes are made out of paper these days. A certain thickness of paper is recommended though.
There is a lot of plastic that can be laser cut. Many plastics are extremely suitable and no post-processing is required since the edges are melted in a way that makes them appear polished.
POM is perhaps the most widely used plastic in the industry. It can have a variety of functions. It is used for gears, guiding and sliding applications, medical instruments, food packaging, etc…. The ability to create complex laser shapes from POM is perhaps the most important reason for its versatility.
As described above, laser cutting via the thermal stress fracture method is very suitable for glass. Cutting complex shapes from glass would be very challenging without the use of laser cutting machines.
Textile and leather
Laser cutting for fabrics and leather has recently become enormously popular. It is done on the principle of laser embroidery. You can make a lot of embroidery designs from cotton, nylon, polyester and other fabrics.
Materials not suitable for laser cutting
Laser cutting machines also have their limitations, below are some materials that are best not cut with a laser.
Polycarbonate discolors when you laser cut it. So the cut product is no longer beautiful once you are done with it. There is also a high risk of fire.
ABS is a plastic type that resists impact. It is refractory, strong, hard and works well in electrical applications. A very handy type of plastic. However, when you go to laser them it becomes a mess. Most plastics evaporate when cut. ABS does not, it melts and becomes liquid. The result is a sticky work table and a cutting surface that no one would be happy with.
PVC or is a very versatile plastic. It is used in pipes, cables, synthetic leather, etc…. However, it is highly unsafe for laser cutting. This is because the chlorine in the product is released when it is heated. This can be extremely toxic to the user and also harmful to the machine itself because it is extremely corrosive and thus can corrode your cutting head.
HDPE stands for high density polyethylene. It is best known for its use in bottles. However, it reacts somewhat similarly to ABS when you laser it.
Polysterene and polypropylene foam
These plastic types pose a high fire hazard.
Everything that is glued
Laminate, wood or plastics can be cut very well, but if they already contain glue, be very careful. Adhesives burn hard during cutting which can create dangerous situations and seriously damage your cutting head.