Coined from the words Light Amplification by Stimulated Emission of Radiation lasers have been a byword for efficiency and quality in materials processing since their advent in the sixties.
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They offered an entirely new form of energy which in turn lent itself to uses in manufacturing, medicine and communications. Able to heat, melt and even vaporise material, lasers are seen as the ideal medium for channelling intense but controllable energy.
By far the most popular use of lasers is for cutting.
Laser cutting is mainly a thermal process in which a focused laser beam is used to melt material in a localised area. A co-axial gas jet is used to eject the molten material and create a kerf. A continuous cut is produced by moving the laser beam or workpiece under CNC control. There are three major varieties of laser cutting: fusion cutting, flame cutting and remote cutting.
In fusion cutting, an inert gas (typically nitrogen) is used to expel molten material out of the kerf. Nitrogen gas does not exothermically react with the molten material and thus does not contribute to the energy input.
In flame cutting, oxygen is used as the assist gas. In addition to exerting mechanical force on the molten material, this creates an exothermic reaction which increases the energy input to the process.
In remote cutting, the material is partially evaporated (ablated) by a high-intensity laser beam, allowing thin sheets to be cut with no assist gas.
The laser cutting process lends itself to automation with offline CAD/CAM systems controlling either three-axis flatbed systems or six-axis robots for three-dimensional laser cutting.
Improvements in accuracy, edge squareness and heat input control means that the laser process is increasingly replacing other profiling cutting techniques, such as plasma and oxy-fuel. There are many state of the art laser machines on the market for cutting purposes, which can be used to cut metals, woods and engineered woods.
Cutting characteristicsBenefitsThe laser cutting process involves focusing a laser beam, usually with a lens (sometimes with a concave mirror), to a small spot which has sufficient power density to produce a laser cut.
The lens is defined by its focal length, which is the distance from the lens to the focused spot. The critical factors which govern the efficiency of the process are the focused spot diameter (d) and the depth of focus (L).
The depth of focus is the effective distance over which satisfactory cutting can be achieved. It can be defined as the distance over which the area of the focused spot does not increase beyond 50%.
The laser focal spot diameter and the depth of focus is dependent on the raw laser beam diameter on the lens and the focal length of the lens. For a constant raw laser beam diameter, decrease in the focal length lens of the focusing lens results in a smaller focal spot diameter and depth of focus. For a constant focus length lens, increase in the raw beam diameter also reduces both the spot diameter and the depth of focus.
To allow comparison between lasers with different beam diameters we therefore use a factor called the focus f-number, which is the focal length, F, divided by the incoming raw beam diameter, D.
The requirements for cutting are as follows:
a) high power density and therefore small focused spot size
b) long depth of focus to process thicker materials with a reasonable tolerance to focus position variation.
Because these two requirements are in conflict with each other, a compromise must be made. The only other consideration is that the shorter the focal length, the closer the lens is to the workpiece, and therefore more likely to get damaged by spatter from the cutting process.
In fact, it would be possible to optimise focal length for each material thickness, but this would involve additional set-up time when changing from one job to another, which would have to be balanced against the increased speed. In reality, changing the lens is avoided and a compromised cutting speed used, unless a specific job has special requirements.
Nowadays most of industrial sheet metal laser cutting is carried out using two types of lasers: CO2 and fibre.
The CO2 laser (carbon dioxide laser) is generated in a gas mixture, which mostly consists of carbon dioxide (CO2), helium and nitrogen. Such a laser is electrically pumped using an electric discharge.
CO2 lasers typically emit at a wavelength of 10.6μm. Those used for material processing can generate beams of many kilowatts in power. The wall-plug efficiency of CO2 lasers is about 10%, which is higher than for most lamp-pumped solid-state lasers (eg ND:YAG lasers), but lower than for many diode-pumped lasers .
A CO2 laser can cut thicker materials (>5mm) faster than a fibre laser of the same power. It also produces a smoother surface finish when cutting thicker materials.
Laser cutting of sheet metals historically started with CO2 lasers. Most CO2 laser cutting machines are three-axis systems (X-Y, two-dimensional positioning control with a Z-axis height control).
There are, however, a number of ways of achieving the X-Y movement: either moving the laser head, moving the workpiece or a combination of both.
The most popular approach is known as a 'flying optics' system, where the workpiece remains stationary and mirrors are moved in both X and Y axes. The advantages of this approach are that the motors are always moving a known, fixed mass. This can often be much heavier than the workpiece, but it is easier to predict and control.
As the workpiece is not moved, this also means that there is no real limit to sheet weight. The disadvantage of flying optics is the variation in beam size, as a laser beam is never perfectly parallel, but actually diverges slightly as it leaves the laser.
This means that without controlling the divergence, there may be some variation in cutting performance between different parts of the table, due to a change in raw beam size. This effect can be reduced by adding a re-collimating optic, or some systems even use adaptive mirror control.
The alternative is a 'fixed optic' system where the laser head remains stationary and the workpiece is moved in both X and Y axes. This is the ideal situation optically, but the worse situation mechanically, especially for heavier sheets.
For relatively light sheet weights, a fixed optic system can be a viable option, but as the sheet weight increases, accurately positioning the material at high speed can be a problem.
The third option is known as a 'hybrid' system, where the laser head is moved in one axis and the material moved in the other axis. This is often an improvement over fixed optics, but still suffers from difficulties with heavier sheet weights.
Fibre lasers are a member of a family called 'solid-state lasers'. In solid-state lasers, the beam is generated by a solid medium. Fibre lasers, disk lasers and Nd:YAG lasers are in the same category.
A fibre laser beam is generated by a series of laser diodes. The laser beam is then transmitted through an optical fibre where it gets amplified (similar to a conventional laser cavity in CO2 lasers). The amplified beam, on exiting the optical fibre, is collimated and then focused by a lens or a concave onto the material to be cut. Fibre laser sources have the following advantages:
Direct diode laser technology is the latest progress in the field of solid-state lasers. In this technology, several laser beams emitted from laser-emitting diodes of different wavelengths are superimposed using so-called beam combining techniques. Unlike fibre lasers, direct diode lasers do not include a brightness-enhancing stage, giving them lower optical losses and higher wall-plug efficiency. However, for the same reason, direct diode lasers are currently of lower beam quality compared to fibre lasers. Direct diode lasers at multi-kilowatt levels of power are commercially available and have been successfully used for sheet metal cutting applications.
Laser cutting is an important industrial process that is rapidly becoming the primary method for cutting materials. It offers faster and cleaner results with less labor and overhead costs than most other approaches. A laser cutter uses a coherent light source to produce a collimated beam of light energy. It is then focused on a small spot on the surface of the material to be cut.
Given the proper type of laser, nearly all material types can be cut this way. Sheets of hardened steel and complex composites 100 mm thick pose no challenge when the equipment and operation are optimized.
Listed below are the 8 steps of the laser cutting process:
Workpieces must be properly prepped in order to ensure a precise cut. Laser cutting can be performed on a wide spectrum of materials, including metals, plastics, composites, glass, rock, fabrics, and more. However, lasers create hazards when applied to certain materials, and other items may not respond well (or at all) to laser cutters. For example, PVC produces highly toxic chlorine gas when burned, and ABS (acrylonitrile butadiene styrene) simply pools and bubbles rather than cutting. Additionally, laser systems can only cut materials up to a certain thickness limit. The limit depends upon the absolute laser power, the beam quality, and the absorption spectrum of the material.
To prep the laser cutter, first securely position the workpiece on the laser cutting bed. Load the design into the cutter's computer system. Validate that the file is composed of single lines, without color or layer issues that might interfere with the cutter software. Check that the laser cutting parameters such as laser power, speed, focal length, gas assist, etc. are suitable for your project and material. Ensure that your machine's extraction and filtration systems are functioning and that the workspace has adequate ventilation.
Laser light is generated through a process called stimulated emission (LASER means Light Amplification by Stimulated Emission of Radiation). It begins with a laser medium ' a solid, liquid, or gas (unique or blended) whose atomic structure can be excited to higher energy levels. The medium is pumped with energy to generate these higher energy states. This can be done through electrical discharge, optical (flash tube, another laser, etc.) pumping, direct electrical stimulus at a semiconductor junction, or chemical reactions that generate flashes of energy emission.
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When a photon of the correct energy interacts with an atom in this excited state, it stimulates the emission of an additional photon. The atom briefly enters a higher energy state that cannot be sustained. This stimulated emission process creates two photons that are identical in terms of their energy, phase, direction, and polarization. The newly emitted photon is in phase with and moves in the same direction as the incident photon, which leads to the amplification of light. A chain reaction of these photomultiplication reactions generates a stream of coherent photons within a narrow frequency range.
These generated photons are reflected between mirrors placed at either end of the laser medium. This creates an optical cavity or resonator which allows the photons to build up in intensity through multiple passes. However, one of the mirrors is partially transparent, allowing a predictable proportion of the light to exit the resonator as a coherent beam.
The process of focusing a laser requires the manipulation of the laser beam to draw its energy into a smaller area. This is typically done with lenses or mirrors and improves the specific energy, power density, and precision in applications such as: cutting, drilling, welding, or laser microscopy. A smaller focal spot results in a narrower cut and a longer focal length creates a more uniform kerf.
There are various ways to focus the beam, depending on the laser system's characteristics. A convex lens or converging lens is the most common solution. Diffraction within the lens bends the light rays, causing them to converge at a 'focal point' a specific distance from the lens surface. The distance between the lens and the focal point determines the degree of beam convergence or divergence. The beam's quality, meanwhile, defines how small that spot can be, and becomes the limiting factor of the laser's specific energy at the 'work' point.
Mirrors can also be used to focus beams, functioning in much the same way as those in a reflecting telescope. Concave mirrors are designed to make reflected light converge at a single point. Mirrors can be used alone or in combination with lenses for energy concentration.
In higher-end systems, particularly those requiring extreme precision, adaptive optics enhance beam control in real time. These systems use digitally controlled, deformable mirrors or variable-focal-length lens systems to correct for distortions and aberrations in the beam caused by imperfections in the optics or transient obstructions. Since they actively monitor and adjust the focal length, the beam can be focused and maintained at optimum quality.
The machine's laser cutting parameters need to be optimized in order to get the best possible quality out of the cut. The laser energy level is the main driver in determining the beam's intensity, which, in turn, affects cutting speed and depth. Higher power settings allow for faster cutting but may result in a larger HAZ (heat-affected zone) if not properly tuned. HAZ size is directly related to beam power, beam conditioning, and the response of the target to the incident energy. Speed significantly affects the quality of the cut and the process's productivity. Higher cutting speeds generally produce smaller heat-affected zones, as there is less time for heat to spread out from the laser's point of incidence. However, high speeds may also mean that melt residues don't clear the cut but instead bubble into a rough, imperfect cut.
Adjust the focal point of the laser beam to a position at the material surface or slightly below it. This increases the specific energy (power per unit area) at the critical cut initiation point by minimizing the spot size. In some cases, you may want to set the focus below the upper surface of the target to control the form of the kerf or cut zone.
Select the diameter of the gas assist nozzle based on the material thickness and desired cutting quality. Smaller nozzle diameters provide finer cuts while larger nozzles may allow faster cutting speeds and better clearance.
It takes time to pierce through any item and thicker materials take longer. The exact values depend heavily on the material thickness, type, and laser power and should be determined by a test.
The kerf width refers to the width of the cut made by the laser. It is influenced by several factors, including laser power, cutting speed, focal quality, and material properties. The kerf width must be carefully considered when manufacturing parts with tight tolerances.
In some cases, the material benefits from preheating or post-heating. Preheating improves the cutting process because the laser doesn't have to do as much work to get all the way through thick workpieces. Post-heating reduces residual stresses in the cut areas which might distort the part.
Differences in materials will demand that you adjust the cutting parameters. Reflectivity, thermal conductivity, and melting point influence the machine's ability to start or continue a cut. Consult material-specific guidelines and perform test cuts to determine optimal settings.
Start out with the manufacturer's guidelines for the specific laser system and material being cut. Test cuts will show you which adjustments to make to your parameters. You'll likely need multiple test iterations in order to fine-tune your setup for complex projects.
Once the machine parameters are validated by testing, the cutting process can begin. The laser cutting machine will follow its programmed instructions. The beam rapidly heats and vaporizes the material. The gas assist blows vapor and droplets clear and cools the post-cut areas, creating a narrow kerf along the desired cutting path.
For larger cutting jobs or when cutting multiple parts, the laser cutting machine will operate continuously unless forced to pause to reposition the workpiece or clean the nozzle. More capable equipment may 'observe' other reasons for stoppages or operator intervention.
After the cutting is complete, the cut parts will often need to undergo additional post-processing steps such as cleaning, deburring, or surface treatment before the product can be called complete.
Programmed movement is achieved either by moving the cutting table or the optics head (or occasionally both). Larger machines typically have mobile optics because the optical head has far less mass than a large workpiece, allowing for faster maneuvers. Move time between cuts can suck up significant process time, especially when large plates and heavy loads must be positioned. Smaller industrial machines with lower cutting capacities will commonly move the cutting platform along at least one axis of motion because it simplifies the optical setup. Desktop machines, meanwhile, commonly feature fixed lasers, so all motion is made by the cutting table.
In all cases, the motion is controlled using a G-code-based CNC approach. Motion is driven by stepper motors in smaller machines and often by closed-loop controlled DC motors on larger machines. These positioning motors get movement instructions from the G-code which the computer controller converts into motor drive and positioning instructions.
Gas assist serves a range of purposes in laser cutting. Melt material and ash removal is usually the most critical function of gas assistance. Natural materials generally char at the cut point and the remains are blown away. Metals may partially vaporize but most of the residue in the kerf is molten material that needs to be cleared, exposing further depth in the cut zone. The fast-moving gas also serves to cool the surrounding uncut material and minimize the HAZ.
Many materials release smoke and vaporized material when cut. This can deposit residues onto the surrounding material or onto the optics, either reducing the product's surface quality or disrupting beam intensity and quality. Gas assist helps to keep the whole cut area and optics clear of these effects.
In some cases, the gas assist can enhance the cut process more directly by introducing oxygen into the cut. Some of the material can be oxidized and/or literally burnt away. This is particularly valuable when cutting thick steel items.
Cut parts will remain in place on the cutting table at the end of cutting operations. They can be safely removed once the laser is turned off and the machine has ceased movements. Take care, though, because cut parts can have sharp edges and hot residue.
Laser cutting is a very high-temperature process, so give the parts sufficient cooldown time before handling them. You also may need to make special handling considerations to prevent damage; many items can get scratched if they're stacked without interleaf protection.
Important finishing processes may include: deburring, stress relief operations, chemical or mechanical surface cleaning, etching, plating, painting, and careful packaging to maintain the finish.
A laser cutting machine generates a high-energy laser beam that is then directed to the optical cutting head via light pipes or mirrors. The cutting head optics focus the coherent energy on a small spot. That heats the target material until it melts, chars, or vaporizes. Any remaining char, smoke, or melted material is then blown clear of both the cut and the optics apparatus to allow the cut to penetrate deeper and progress along the cut path.
An X-Y transport mechanism moves either the workpiece, the optics head, or a combination of the two so that the laser traces out the preprogrammed cutting path until the finished part can be extracted from the sheet material. For more information, see our guide on How Do Laser Cutters Work.
Ruby-laser cutting machines were the first type to be successfully created by Western Electric in the mid-s. These devices worked at low power outputs and the earliest cutting applications involved drilling fine holes in diamond dies. Boeing was the first company to experiment with CO2 lasers to cut otherwise intractable materials. The first marketed laser cutting machines were developed by Western Electric, with sales beginning around .
New laser types and improved cutting techniques have expanded the sector to the point where some laser cutters are small and cheap enough for home use and others serve in large-scale manufacturing.
A laser cutting machine is a specialist CNC device with generally low operational overheads. The machine generates a high-energy beam of coherent light radiation with an integral resonant chamber. A collimator tunes the beam to ensure its divergence is minimized. It directs the beam, either via mirrors or light pipes to a focus apparatus. Then optics/lenses focus the beam on a small spot to concentrate the energy and initiate a cut. The energy melts and/or vaporizes material along the programmed cut line. In some cases, it needs more than one pass to cut through the workpiece's entire thickness. Air assist blows char, smoke, and melted material from the cut to clear it and cool the surroundings. A CNC axis system moves either the laser optics, workpiece, or both in the necessary motions to complete the cut process. This is usually done in only two dimensions (the X-Y plane), but some machines create contoured surfaces by adding Z-axis motion. In some cases the motion can have additional axes, to allow closer conformance to rounded pipes or even more complex 3D objects. For more information, see our guide on the Use of Laser Cutting.
Certain materials require specific laser types (e.g., CO2, fiber, or solid-state lasers) and adjustments to the power, speed, and type of assist gas.
Laser cutting is applicable to most metals and plastics, wood, fabrics, composite materials, glass, and ceramics, including:
Laser cutting offers advantages over many other manufacturing processes. Some of the advantages include:
Although laser cutting offers many advantages over more traditional methods, there are issues to consider and barriers to some manufacturing applications. Some disadvantages include:
Low-powered home/hobby machines start at a few hundred dollars. Despite their limitations, such machines are widely and effectively used in many applications. Large industrial machines with laser powers in the tens of kilowatts can cost up to $1,000,000 and require special facilities and support equipment that add to this cost.
Yes, laser cutters can run at different laser power settings. They are designed for a wide range of tasks. Paper- and card-cutting lasers may need less than 10W while large industrial machines are available with 10+ kW lasers.
Yes, with the correct setup, parameters, and power, many laser cutters can handle various thicknesses of stainless steel. For more information, see our guide on Lasers For Cutting Stainless Steel.
Yes, some laser cutters can also do engraving. The difference between laser cutting and laser engraving is only how deep a cut is made. Laser engraving demands more precise power and throughput control than laser cutting. For more information, check out our guide on What is Laser Engraving.
This article presented the laser cutting process, explained each step, and discussed them in detail. To learn more about laser cutting, contact a Xometry representative.
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