A Comprehensive Guide to Sheet Metal Laser Cutting
Learn more about the history of this process and when to best use it.
Metal laser cutting goes as far back as the 1960s with early machines needing lots of power to operate. Today, laser cutters are now capable of cutting a variety of metals, including: steel, titanium, aluminum, brass, and copper, with extreme precision and speed. Laser cutting is now a key manufacturing method for low- and mid-volume components, heavy machinery parts, and aerospace manufacturing. This article will discuss the process of sheet metal laser cutting, its history, advantages, disadvantages, and the types of lasers for sheet metal cutting.
Sheet metal laser cutting uses a highly concentrated, coherent beam of light. This light is directed through a collimation and focus apparatus to deliver a focal point intensity high enough to vaporize and/or melt most metals. By this means, the target material can be cut to extract a net shape result that precisely reflects the design intent in the virtual model.
By transporting the optics head, or the laser and optics entirely—and in some cases also moving the target material in one or two axes of travel—the high-intensity energy cut point can travel over a work table. It produces identical accuracy and cutting outcomes to the edge of the machine's total sheet/plate capacity.
The history of metal laser cutting began with the first lasers, in the early 1960s. By 1965, Kumar Patel at Bell Labs made a machine capable of cutting metals. Early machines required a lot of power to operate. However, the development of CO2 lasers in the 1970s improved efficiency and practicality. By the 1980s, the technology had become advanced enough to move out of research and military manufacture and into the mainstream.
The development of fiber lasers in the early 2000s increased power efficiency and led to machines that produce higher-quality cuts. Computer-aided design (CAD) and computer-aided manufacturing (CAM) software has increased the accessibility of laser cutting, as have small and low-cost home-use machines that are increasingly widespread and capable.
Laser cutting was first used in the 1960s when Bell Labs was a key contributor to the US space program. The earliest experiments with laser cutting were performed on sheet metals, as a way to ease production difficulties in aerospace manufacturing. The company developed laser cutting as a way to process difficult-to-cut materials like titanium and stainless steel.
The advantages of sheet metal laser cutting are listed below:
- Zero Distortion Cutting: No force is applied, so no shear, pressure, or abrasion distortion of the material is involved.
- Low Heat: To be effective, other processes that use heat (plasma cutting, gas torch) induce localized heating or even require preheating of the target. Local heating in sheet metal creates serious distortion. Laser cutting vaporizes the cut path before significant heat can be conducted to the surrounding material.
- No Cut Degradation: When the optics are kept in good order, no blunting occurs as the cut progresses, so the last inch of the cut is identical to the first.
- Minimal Material Consumption: The cut width is minimal, unlike grinding or flame cutting.
- Sharp Turns and Smooth Radii: The laser can turn on a point or follow any curvature desired, unlike guillotine or shear cutting.
- Additional Features: Additional complexity in the part makes almost no difference to processing times.
- Fast Processing: The closest “zero force” analog to laser cutting is electrical discharge wire cutting. This offers very slow processing compared with laser cutting.
- Discontinuous Cuts: Stop-start cutting only requires shutting off the beam and repositioning the optics. Features can be disconnected without disturbing the processing.
- Expansion in Sub-Contract Laser Cutting: The expansion in sub-contract laser cutting services means access to leading-edge services does not require CAPEX outlay or in-house skill development.
The disadvantages of sheet metal laser cutting are listed below:
- Cuts are not square but rely on a focused, collimated energy beam. This results in an angled cut that has little effect on thin materials but can be significant in thicker targets.
- The equipment is expensive and must therefore work hard to be cost-justified. Ancillary and maintenance costs can also be high.
- Inert gas assist is required, to blow the cut clean for effective cutting of some metals. Gas consumption is a cost factor.
- Oxygen assist is required, both to blow the cut clean and accelerate the cutting by “burning.”
- Safety issues around laser cutting can be a burden.
- Health issues in laser cutting are significant since laser cutting metal can produce nano-particle dust that poses an operator hazard. Non-metals can produce toxic vapors/smoke, so no cut should be considered user-safe.
The types of lasers for sheet metal cutting are listed below:
Fiber lasers are a growth category and deliver a range of frequencies through simple alterations. Available power levels quickly climbed from a few milliwatts in the early 90s to several kilowatts today.
Fiber lasers use rare earth dopants (minor impurities deliberately added) in silicate or phosphate glass as the active gain medium (the energy amplifier). A diode laser pumps light into the fiber. The dopants react to the photons by releasing more photons, trapped by the fiber into a coherent beam. Alternative dopants (and diode pump sources) generate alternative frequencies in the resulting beam. Fiber lasers are relatively expensive to make, but they have very high electrical power efficiency and longer product life, compared with the more established CO2 technology.
CO2 lasers were the first commercialized in laser cutting, even though they were invented around the same time as the other core laser technologies. Higher powers were achieved more quickly, and the construction of these lasers is technically simpler than others. Their electrical (power) efficiency is poor, compared with other technologies—and the laser device lifespan is short. However, they are lower cost to make and very effective, so the choice is not a simple one.
The CO2 laser works by means of an electrical discharge (AC, DC, or radio frequency) through a gas tube. The tube is filled with CO2, plus small amounts of nitrogen and hydrogen. An arc excites the nitrogen molecules which then transfer their energy to the CO2 molecules. This results in the emission of high-energy infrared photons as they oscillate between high- and low-energy states.
Crystal lasers are often referred to as diode-pumped solid-state lasers or laser diodes. They are semiconductors that, because of the dopants, emit laser light in selected frequency bands. Crystal lasers are a more recent arrival on the laser scene than other technologies. They are power limited at this point, with the highest power devices being a few hundred watts.
They are key to the creation of fiber lasers, as the source that the fiber amplifies. They also have an increasing presence in low-power laser cutting machines.
The procedures used in cutting sheet metal are listed below:
Laser fusion cutting uses an inert gas stream of nitrogen, argon, or a mix of the two. The gas stream cools the cut, blasts away detritus of cut material (clearing the optical path), and suppresses oxidation that would otherwise occur due to atmospheric oxygen exposure.
Laser flame cutting (also called reactive laser cutting) looks to exploit the reactivity of metals. An oxygen stream blasts the cut site which accelerates the cut process by aggressive oxidation.
Sublimation cutting exploits the property of some materials to transition from a solid state to a vapor state without a liquid phase. This allows cutting with little or no residues. It also reduces the opportunity for heat to transfer out of the cut and create a heat-affected zone (HAZ). This technique is possible with some polymers and is particularly applicable to fabrics.
Sublimation cutting requires a higher beam power and better focus. It allows for more precise and damage-free cutting. It is typically used to cut the fine traceries of stents, for example, because of the additional precision and low damage to the remaining material.
The things to consider in using sheet metal laser cutting are listed below:
- Select a machine with a CO2 or fiber laser, as these are better suited to metal cutting.
- Ensure your chosen machine has sufficient power for the maximum thickness of sheet metal you expect to cut. Excess power is a good choice as it gives you flexibility.
- Keep your workspace and machine clean.
- Keep a fire extinguisher on hand.
- Ensure your machine settings are suited to the material you’re cutting.
- Ensure the design is executed correctly for a clean cut in a single pass: No features too close, and no unsupported or poorly supported areas.
- Make a series of test cuts in a waste area of the material, to fine-tune the cut for quality.
- Use all appropriate safety gear such as: shields/covers for the machine, IR-proof goggles, and good extraction.
- Apply sufficient air/inert gas/oxygen assist in ensuring a quality cut and keeping the optics clear of cut residues.
The best laser cutting machine for sheet metal depends heavily on budget and productivity needs, as well as the material thicknesses you need to handle. Listed below are some factors to consider:
- For home use and occasional small business use, the Glowforge® Pro is highly recommended. It is effective for small jobs with its good enclosure, office-friendly design, and 45 W laser.
- DXTech machines cover the entire industrial range and offer great capability for higher demand and higher budget applications.
No, laser cutting in sheet metals is not dangerous if the recommended safety precautions are followed. All machine tools pose some hazards, and laser cutting has a “hot” aspect and coherent light as extra hazards. Small laser cutters are Class 1 laser devices and are deemed safe. Be careful of backscatter if working with the covers open! Also, do not run the machine with the covers open! Additionally, all hot processes carry a fire risk. Keep an extinguisher on hand and within its service date. Use a CO2 type, ideally. Dust from many materials can pose health hazards, so ensure the extraction system is on, working, and clean. Keep the machine clean after use. All in all, the user hazards are minor and easily managed.
This article presented sheet metal laser cutting, explained what it is, and discussed its history and applications. To learn more about sheet metal laser cutting, contact a Xometry representative.
Xometry provides a wide range of manufacturing capabilities, including sheet cutting and other value-added services for all of your prototyping and production needs. Visit our website to learn more or to request a free, no-obligation quote.
- Glowforge® is a registered trademark of Glowforge Inc.
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