Sheet Metal

Laser cutting do’s and don’ts

By June 1, 2020
Laser Cutting Hero scaled

Laser cutting is the process of using high-power beams of light to cut, slice, or bore materials. Developed in the 1960s at the Welding Institute in England, the process has become increasingly popular. In fact, metal laser cutting machines now account for the largest product segment of the global metal cutting market, with demand for these devices expected to increase to nearly $9.8 billion 2025.

So, how does laser cutting work? There are a number of different laser cutting processes, but they generally fall into two categories: fusion cutting and ablative cutting. In its simplest form, laser fusion cutting involves using a laser to melt a localized area of material on the workpiece, then cutting away the molten material with highly pressurized jets of inert gas (typically nitrogen, which doesn’t react exothermically with the cut material). CNC controls can be used to move the laser or workpiece to create continuous cuts.

Ablative laser cutting uses rapid pulses from a high-intensity laser to remove material a layer at a time. This process actually evaporates rather than melts, and therefore doesn’t require pressurized gas to remove excess material. Generally a slower process, ablative laser cutting is used to make partial cuts that don’t pass through the workpiece from top to bottom (laser engraving, for instance, is an example of an ablative process). In contrast, fusion cutting fires lasers in continuous waves or longer pulses, and therefore can only be used to cut all the way through the workpiece.

Why choose laser cutting?

Laser cutting offers a few distinct benefits. Principal among them is its ability to create extremely precise and accurate parts. Some parts can have tolerances of less than 1mm, which makes the process of laser cutting an efficient method for parts with intricate or complex features. The highly localized nature of laser cutting drastically reduces the risk that the workpiece material will warp, and pieces produced via laser cutting oftentimes do not require post-processing treatment or surface finishing.

Further, metal laser cutting does not require changing tools between operations, allows for more flexibility in design due to lack of fixed tooling, and can be highly automated, minimizing labor costs and shortening production times. Additionally, since the beam is the only tool that touches the workpiece, there’s no mechanical friction causing tool wear in the process.

Laser cutting is extremely common in industrial manufacturing, and is well-suited for producing pieces like automobile bodies, phone cases, and sheet metal. The process also finds extensive applications in the aerospace, medical, and shipbuilding sectors.

Key considerations for laser cutting

While CNC laser cutting machines are commonly used in manufacturing, effective laser cutting generally requires the input of skilled engineers following best practices. Here are three key laser cutting considerations for engineers and machine operators to keep in mind:

The material should determine the specific laser cutting process

While metal laser cutting machines garner a lot of attention, lasers can also be used to cut or engrave ceramic, wood, thermoplastics, and polymers. Engineers should select the laser cutting process best-suited to the part’s material.

Fusion laser cutting, for instance, is effective for cutting most metals and thermoplastics, whereas ablative laser cutting can be extremely efficient at cutting parts made of acrylic and polyacetal because their melting and boiling points are so close, enabling evaporation.

On the other hand, some materials are more difficult to cut with lasers. Thermoset polymers and organic materials like wood, for instance, burn rather than melt when exposed to a laser — a quality that allows for engraving or branding, but not precise cutting.

Don’t mistake an increase in laser power for an increase in efficiency

While increased laser power does mean that it’s possible to cut faster — with new developments making it possible to reach cutting speeds up to a meter per second — more raw power doesn’t directly translate to more efficient manufacturing.

To reach these high cutting speeds, the laser needs time to accelerate, which makes high wattage lasers incredibly effective for cutting large parts or parts without intricate features. These lasers offer fewer advantages for parts with complicated geometries because the laser typically has to move to another cut before it can reach full speed. Acceleration and deceleration must be taken into account when considering laser cutting efficiency.

Design the parts to align with laser cutting process requirements

It’s a common mistake to assume that the kerf width is so narrow as to be insignificant. Lasers create incredibly thin cuts — typically between 30 and 300 microns, depending on the laser wattage, setup, and process — but those kerf widths still need to be factored into the cutting design so that the resulting part remains suitable for its intended application.

Another crucial design consideration is tabbing, or the use of micro-joints to support small parts. The highly pressurized gas used in fusion cutting requires that parts be able to support their own weight, which often comes down to part thickness. Typically, part thicknesses of 2-3mm or more will be fine without tabbing, but if part thickness is less than 2mm, designers may need to add micro-joints to stabilize the part during the cutting process and prevent the pressurized gas from moving it. It can also prevent loss of and facilitate removal of small parts from the machine. These tabs can be removed easily during post-processing.

Comply with critical safety requirements

Safety is of the utmost importance in manufacturing. Only trained professionals should use laser cutting equipment. Depending on the material in use, the process can also emit harmful and toxic gasses, so employing regulation-compliant air pollution control equipment is crucial.

Laser cutting: Every detail drives efficiency

When used correctly, metal laser cutting machines promise accuracy, precision, and efficiency. While the complex material and design considerations at play mean that product teams and engineers must take a little more time upfront to ensure designs are optimized for manufacturing, the quality of resulting parts generally speaks for itself. To ensure parts are manufactured at the highest quality and speed, consider partnering with an expert on-demand manufacturer.

Fast Radius provides superior, on-demand digital manufacturing services ranging from laser cutting and urethane casting to injection molding and 3D printing. Working closely with customers during every stage of production, our team of experienced designers and engineers provide end-to-end support. From design all the way through post-processing and fulfillment, we’ve organized our workflow to create the high quality parts that customers need, when they need them. Ready to get started? Contact us today.

Visit our website to learn more about the services we provide, and check out our resource center to learn how digital manufacturing applications are used in the real world.

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