How exactly do laser cutters work?
Since the invention of the CO2 laser in 1964, laser cutting technology has grown considerably.
Laser cutters are now more powerful and affordable than ever making them accessible for even hobby users.
This article gives a detailed overview of laser cutters, their working, and the factors that affect their performance.
How does a laser cutter work?
A laser cutter works by using a high-energy laser to vaporize materials, producing a cut edge. The laser is focused on the material through an optical arrangement and a computer system (CNC) translates the G-codes to guide the laser head to follow the pattern to be cut.
Using a jet of gas to blow the molten material out of the cut facilitates the cutting process and enhances the ability of the laser to produce clean cuts.
The process of using a laser cutter to cut or engrave a material consists of various steps that ensure a successful outcome.
A laser cutter is basically a CNC machine similar to a 3D printer, that uses a laser module as the cutting tool.
To perform laser beam machining, the very first requirement is to have access to a good laser cutter capable of performing the required job.
After having access to the laser cutter, a few easy steps are to be followed to begin the laser cutting or engraving process.
Preparing the Design
Having a good CAD design is necessary to produce good quality output.
There are various laser cutter/engraver software available for designing and translating the design into G-codes.
Depending on the type of process to be performed (cutting or engraving), you can create a vector or raster design.
You can also use the readily available laser cut files from various websites.
Download the file from the website and import it to the laser software to begin the cutting or engraving process.
Another essential software for operating a laser cutter is a G-code sender software such as LaserGRBL or Light Burn.
This software takes the CAD design as the input and sends out the corresponding G-codes to the controller of the laser cutter.
Furthermore, a good nesting software will enhance the efficiency of the process by rearranging the design and minimizing the material wastage.
CNC nesting also reduces tool travel and further improves the productivity by reducing the machining time.
After the designing process, the next important step is to set the optimum parameters for the process.
Setting the Parameters
This is one of the most tricky parts of the laser cutting or engraving process and requires experience to set it right.
The optimal parameters depend upon the specifications of the laser cutter being used and the type of material being cut.
Performing test runs before starting the actual process is always a good practice to make sure that the quality of the output is as desired.
Starting the Process
After setting everything up and performing the test run, you can begin the actual cutting or engraving process.
On starting the process, the laser source generates the laser light, which then travels through various components to perform the desired action.
Beam Delivery System
It consists of a series of mirrors or reflective surfaces that guide the laser from the source.
These mirrors are strategically placed to reflect the laser beam and guide it towards the cutting head.
The beam delivery system of CO2 and Nd: YAG lasers comprises of series of mirrors that require regular maintenance.
Mis-alignment of these mirrors will result in loss of laser energy and affect the laser beam quality.
Whereas the delivery system of a fiber laser consists of a fiber optic cable that requires comparatively less maintenance.
The cutting head consists of a focusing lens that converges the laser into a narrow beam with a small spot size.
This conversion of laser into a highly focused beam increases the energy density of the laser beam.
The laser beam then passes through a nozzle where a pressurized auxiliary gas accompanies it.
Depending upon the type of material and its thickness, the auxiliary gas can be oxygen, nitrogen, argon, etc.
Auxiliary gas is recommended for cutting thick materials as it enhances the cutting process by blowing out the molten metal from the kerf.
It is generally not used for the engraving process as it can produce unwanted splatter on the engraving surface.
The focal length of the lens used in the cutting head determines the optimum distance between the workpiece and the nozzle.
This distance between the workpiece and the nozzle determines the position of the focal point on the workpiece.
Changing the focal point of the laser directly affects the cutting speed and the quality of the cut.
Linear Drive System
A laser cutter generally uses a linear drive system such as chain, belt, or rack and pinion mechanism.
The G-codes sent to the controller of the laser cutter define the movements of the linear drives to perform the desired cut or engraving.
This linear drive system enables precise movement of the laser head for producing precise cuts and high-quality engravings.
However, some laser cutters use a galvanometer-based optical system that uses precise movements of mirrors to change the position of the laser on the workpiece.
Galvo-based lasers have faster positioning speed but have a comparatively smaller work area.
Laser Cutting Process
When the laser beam strikes the surface, the workpiece material absorbs the laser energy and converts it into heat energy.
This heat energy raises the temperature of the material high enough to melt and vaporize the material.
Based on the type of auxiliary gas used, there are three different cutting processes.
|Aluminum and Stainless steel
|Mild-steel, carbon steel, etc.
|Thin sheets of metals, plastics, wood, etc.
Various types of laser cutting processes
In fusion cutting, the auxiliary gas does not assist in melting the material but only comes into action after the laser melts the material.
An inert gas (nitrogen) is generally used as auxiliary gas to assist the cutting process.
The pressurized auxiliary gas blows the molten metal out of the kerf, increasing the cutting speed and reducing the laser power required to cut through the material.
This type of cutting is also known as melt and blow cutting.
In flame cutting, the auxiliary gas (oxygen) actively takes part in the burning and melting of the material.
The laser beam heats the material, and the oxygen reacts with the hot material to start a fire.
This increases the energy input to the material and assists the laser beam to cut through the material.
Due to the reaction between the oxygen and the hot material, this type of cutting is also known as reactive cutting.
Sublimation cutting occurs when thin sheets of material are cut in the absence of auxiliary gas.
A high-energy laser beam evaporates the material layer by layer without forming a molten pool.
This type of cutting is also known as vaporization cutting.
Types of Laser Cutters
A laser cutter works on a principle similar to using a magnifying glass to burn a piece of paper by focusing the sun’s rays on it.
Instead of the sun’s rays, laser light is focused on the workpiece, which then increases the temperature of the surface to burn, melt and vaporize the material.
Depending upon the source of light, there are different types of lasers that are used in laser cutters.
|CO2 (Gas laser)
|9,300 - 10600
|Cutting and engraving metals and non-metals
|Nd: YAG (Solid state laser)
|Cutting metals and engraving some plastics
|Fiber (Solid state laser)
|950 - 2200
|Cutting and engraving metals only
|Diode (Solid state laser)
|550 - 950
|Cutting and engraving metals and non-metals
Types of lasers used in laser cutters
CO2 Laser Cutters
A CO2 laser consists of a gaseous mixture of carbon dioxide, nitrogen, helium, and hydrogen in a glass tube.
A high-voltage electric current is passed through the glass tube that excites the atoms of these gases.
The excited atoms release the excess energy in the form of light.
This light gets reflected between a fully reflective mirror on one end and a partially reflective mirror on the other end of the glass tube.
A high-energy laser beam with a wavelength of 9,300 - 10600 nm is obtained from the partially reflective mirror end.
Nd: YAG Laser Cutters
The term Nd: YAG stands for Neodymium-doped Yttrium Aluminium Garnet.
It is a solid-state laser that consists of an Nd: YAG rod and a krypton arc lamp inside an elliptical reflector.
The light energy from the arc lamp is reflected by the walls of the elliptical reflector and absorbed by the Nd: YAG rod.
This excites the Neodymium ions in the Nd: YAG rod, and excess energy is released in the form of bright light.
Similar to a CO2 laser, this light then gets reflected between a fully reflective mirror on one end and a partially reflective mirror on the other end of the elliptical reflector.
A high-energy laser beam with a wavelength of 1060 nm is obtained from the partially reflective mirror end.
Fiber Laser Cutters
A fiber laser is also a solid-state laser (DPSSL) that uses a semiconductor diode as a light source.
The light emitted by the diode enters the core fiber, which is doped with a rare-earth element (ytterbium, erbium, or thulium).
These rare-earth elements absorb the light from the diode source and transform it into a laser of desired wavelength (950 nm to 2200 nm).
Diode Laser Cutters
A diode laser is a solid-state laser that directly uses the light emitted by a semiconductor diode, eliminating a doping medium.
These lasers are generally used in cheap laser engravers that offer low laser-power output, capable of cutting and engraving thin sheets of materials.
However, recent developments have made it possible to have high-power diode lasers capable of cutting through thick materials.
Laser Cutting vs Engraving vs Marking
A laser cutter is a flexible machine that can perform various types of processes on the workpiece.
Laser cutting is a thermal separation process in which a high-energy laser is used to cut through the entire thickness of the material.
To perform laser cutting, a vector graphic file is used to send the commands to the laser cutter, which then performs precise movements to cut the material in the required shape.
A vector graphic comprises geometrical shapes, such as lines and curves, that are created based on mathematical equations.
These drawings can be easily scaled without affecting the quality of the image.
Laser engraving is a process in which the laser beam does not cut through the entire thickness of the material.
Instead, it removes some layers of the material, creating a cavity in the desired shape or design.
The primary difference between a laser engraver and a laser cutter is the ability to cut through a material in one go.
There are two types of image files that can be used for engraving a material.
|Type of file
|Laser cutting and vector engraving
|.SVG, .EPS, .CDR, .AI, etc.
|.JPEG, .PNG, .BMP, .GIF, etc.
Vector and raster graphic files
In this type of engraving, a vector graphic file is used to define the pattern and design of the engraving.
This process is similar to laser cutting, but the only difference is the laser power.
For vector engraving, a comparatively lower power setting is used, which enables the laser to remove the surface of the material without performing a through cut.
Vector engraving is a continuous engraving process in which the laser engraves one line or curve at a time.
The raster engraving process works similarly to an inkjet printer that prints the image line by line.
A bitmap image is used to define the engraving pattern to the laser cutter.
An engraving/cutting software, such as LaserGRBL or LightBurn, converts the image into tiny dots.
The number of dots per inch (DPI) defines the resolution of the engraving output.
Raster engraving is a non-continuous process in which the laser follows a rapid on-off pattern while engraving one pixel at a time.
Laser marking is the process in which only the top layer of the material is affected by the laser to produce a permanent mark. This process is sometimes also referred to as laser etching.
It does not necessarily involve material removal. The laser beam interacts with the particles on the surface and causes them to change color.
A subsurface marking can also be achieved by manipulating the focus point of the laser.
Laser Cutters and Their Applications
As the name suggests, a laser cutter uses a high-energy laser beam to cut through various materials.
Depending upon the laser source, these laser beams can be of different wavelengths and colors.
The laser cutter consists of a complex mechanism that directs the laser from the source and focuses it into a very tiny spot on the workpiece.
This ability to focus the laser beam into a tiny spot makes laser cutting ideal for cutting and engraving intricate designs that are not possible by traditional methods.
The highly precise nature of laser cutting has made it extremely popular in manufacturing and medical procedures.
Laser cutters are replacing scalpels in various medical procedures, and research is being conducted to use fiber lasers to break down cancer cells.
The highly focused nature of a laser beam enables it to be used in high-precision medical procedures like eye surgery.
Another major application of laser cutters is in the field of manufacturing.
The cuts produced by laser cutters have a smooth edge with an excellent surface finish and do not require secondary machining.
It is the second most precise machining process that offers high material flexibility, right next to waterjet machining.
However, when comparing laser cutting with waterjet machining, waterjet machining offers higher precision at the cost of machining speed.
Apart from material flexibility, laser cutters also provide process flexibility.
They can be used to perform cutting, engraving, and marking on various materials.
Furthermore, a high-powered pulse laser can also be used for drilling holes in the material.
Laser drilling eliminates the physical contact between the tool and the workpiece, thereby enabling to drill intricate holes without deforming the material.
Designers and artists also use laser cutters to enhance their artwork by engraving intricate designs.
Various factors define the ability of a laser cutter to perform good quality cutting and engravings.
The type of laser used in a laser cutter defines its ability to cut through various types of materials.
Using the suitable auxiliary gas and focusing lens can improve the maximum cutting thickness and engraving outputs of the laser cutter.
Furthermore, a precise linear drive system and a good raster or vector design are vital in producing good quality outputs.
Frequently Asked Questions (FAQ)
What is the difference between laser engraving and etching?
The primary difference between laser engraving and etching is that laser engraving involves the removal of material from the surface, whereas, in etching, the surface undergoes physical alteration without any material removal.
Laser etching heats the top layer of the material, resulting in melting and expanding the surface. This expanded surface creates raised marks on the surface of the workpiece without removing any material.
How does the linear drive system affect the quality of laser engraving?
The linear drive system can directly affect the quality of laser engraving. This effect is more visible on raster engravings as they consist of tiny dots (DPI) or pixels. The higher the DPI of engraving, the higher its quality will be. A highly precise drive system will be able to make precise miniature movements to cover each pixel of the engraving and thus produce a high-quality engraving output.
How does the laser delivery system affect the output of a laser cutter?
The laser delivery system does not directly affect the output of the laser cutter.
However, a misaligned laser delivery system will result in unwanted loss of laser energy and affect the ability of the laser to cut or engrave the material. Furthermore, a good delivery system (fiber optic cable) will need very little maintenance and therefore increase the productivity of the laser cutter.