Understanding Materials and Settings for a CO2 Laser

Applies to: all AEON CO2 lasers

This guide covers the basics of finding the settings to use with your CO2 laser. Whether you are brand new to lasers or already experienced, use it as a foundation for adjusting and refining your settings to suit your needs.

What you need

• Notebook
• Scrap material
• Computer with LightBurn
• Patience

Why there is no single right setting

When it comes to settings, one size does not fit all. What works for one person may not work for another, even on the exact same machine. Small differences in the laser tube, optics, beam path, material and even the climate lead to different results. Understanding what your machine can do, and learning to run your own experiments, is the key to finding the right settings.

The scientific method

Asking someone else for settings is tempting at first. To master your laser, though, go back to your school days and the scientific method: form a hypothesis, test it, then revise it based on the outcome. The key is to change only one variable at a time, analyze the result, and draw your conclusion. Trial and error alone is frustrating, and even a lucky result is short-lived.

Operating a laser well is about controlling how a piece of material burns. The more control you have over the burn, the better the results. Knowing which variable to adjust, and when, is what makes you proficient.

What a CO2 laser can do

The machine uses electricity to generate light. That light is focused, and the focused light vaporizes the material in its path. There are five outcomes you can achieve, all of them burns of different depths. There are a few exceptions, but this is a good place to start.

• Engraving: removing material by vaporization so that a depression is left behind. Depth is controlled by the intensity of the beam, the speed at which it passes over the material, or both.
• Ablating: removing the surface layer of a coated material by vaporization, such as burning the anodized or painted layer off a steel tumbler. The result is relatively smooth, with great contrast and little or no surface penetration.
• Etching: a splintering effect that gives a superficial finish, sometimes rough or grainy to the touch. It is commonly used to mark glass, or metal with the aid of a metal marking spray or tape.
• Cutting: severing a piece of material into multiple pieces.
• Scoring: creating a fine groove for an outline. It is a cut that intentionally does not pass all the way through.

Every CO2 laser we offer can engrave, ablate, etch, cut and score. The only limits are the type of material and how thick a material your machine can cut effectively.

Keep a log

A lot of trial and error can go into finding the perfect settings, especially for materials that melt easily. When you find a combination that works, write it down. Keep a spreadsheet or journal with this information for every material test:

• File name
• Material type (SKU or source)
• Material thickness (in or mm)
• Focal lens (in or mm)
• Focus depth (mm)
• Speed (mm/s)
• Power (%)
• Lines per inch (LPI) or interval
• Air pressure (PSI)

LightBurn also has a built-in material library for logging the settings you use.

Materials

Next, pick the material. Consider how you want the final product to look and whether the material can be worked with a CO2 laser. Always check the Material Safety Data Sheet (MSDS) before using a material, so you can take the proper precautions.

Material characteristics

The characteristics and composition of a material matter when you look for settings. Acrylic behaves differently from wood, and wood behaves differently from stone. Each batch of a material can also differ from the last. This happens often with plywood, where a change in the adhesive between the plies can mean your old settings no longer give the results you are used to.

The main variables are:

• Chemical composition: this plays a large part in how a material reacts to laser energy. Materials with complex chemical structures, such as polymers and composites, can engrave differently from simple materials like wood.
• Absorption properties: a material must absorb laser energy at the wavelength of the laser to engrave efficiently. CO2 lasers operate at around 10.6 micrometers (µm), which is absorbed best by darker materials. Darker materials may need less power, and lighter materials may need more.
• Thermal properties: thermal conductivity, melting point and vaporization point affect how a material responds to the heat of the beam. Materials with low thermal conductivity can be more prone to heat damage or melting.
• Surface finish: smoothness, texture and porosity influence engraving quality and resolution. Smooth, uniform surfaces usually give sharper detail and finer lines.
• Density: materials with uniform density engrave more consistently. Variations in density can cause uneven depth or quality.
• Additives and coatings: additives, coatings and surface treatments can change absorption, thermal conductivity, surface texture and overall engraving quality.
• Moisture content: this matters most for organic materials such as wood, paper and textiles. High moisture can cause steam, charring or uneven engraving, so properly dried material is preferred.

Laserable materials

A laser can be used on a lot of materials, and each reacts differently depending on its composition and the settings used. Some common ones are listed below.

1. CO2 lasers only mark metals that are anodized or treated. A CO2 laser cannot engrave bare metal, but you can use a marking spray: the laser fuses the spray to the surface and leaves a dark mark. You can also engrave coated metals, such as powder coated tumblers.
2. Hardwoods, such as mahogany, are difficult or impossible to cut.
3. Plastics can release toxic gases when cut or engraved. Many plastics are dangerous to cut, so know exactly which kind you plan to use.
4. Chromium tanned leather and some artificial leather can release toxic gases. Make sure the leather you use will not.

Unsafe materials

The materials below are known to be unsafe or impossible to use with a CO2 laser. They pose serious risks to your health, your machine or the environment.

• Materials containing chlorine or chloride: this includes PVC (polyvinyl chloride) and vinyl. Under the heat of the beam they release chlorine gas and harmful particulates. Inhaling these fumes is a serious health risk, and the fumes also pollute the air if they are not contained.
• Chromium tanned leather and artificial leather: hexavalent chromium is a toxic compound that can be produced when leather is tanned. Leather treated with it releases harmful fumes and particulates under the beam, and inhaling them is a serious health risk.
• Resin-based materials: this includes fiberglass and carbon fiber products. Resin releases toxic fumes containing volatile organic compounds (VOCs), including formaldehyde. Some resins contain flammable additives or accelerants and can ignite under the beam.
• Plastics: this includes ABS (acrylonitrile butadiene styrene), HDPE (milk bottle plastic), polystyrene foam and polypropylene foam. These release toxic fumes containing VOCs, including chlorine and cyanide. Some plastics contain flammable additives and can ignite under the beam.
• Metal: the 10.6 µm wavelength of a CO2 laser is not absorbed well by most metals. Metals reflect most of the laser energy, so CO2 lasers are not efficient at cutting or engraving them. The reflection can also damage the laser optics and other components.
• Highly reflective materials: this includes thick polycarbonate, Lexan, graphite and mirrored surfaces. As with metal, the reflection can damage the laser optics and other components.

Settings

With an understanding of the machine and the material, it is finally time for settings. Settings control the burn by deciding how long the beam stays on the material. The more finely you tune them, the more controlled the burn.

The four variables

Consider four variables before you start a job: speed, power, lines per inch (LPI) or interval, and focal depth.

Speed (mm/s)

Speed is how quickly the laser head moves across the material while cutting or engraving. On our machines it is most commonly measured in mm/s.

• High speeds (600 mm/s and above) generally give a lighter engrave, because the laser spends less time on each spot.
• Medium speeds (100 to 600 mm/s) give a deeper, more intense engrave, because the laser spends more time on each area.
• Low speeds (50 mm/s or less) are best for cutting.

Example: Imagine moving your hand over a candle. The slower you move, the more heat you feel. Move too slowly and you get burned. Move fast enough and you feel nothing at all.

Power (% and wattage)

Power is the intensity of the beam: how much energy the laser delivers to the material. Power is measured in watts (W), but the software sets output as a percentage of the total wattage available. For example, 50% power on a 60 W tube is about 30 W of output.

Higher power gives a deeper engrave with more material removed and darker, more pronounced marks. Lower power gives a lighter engrave, suited to shallow marks and delicate designs.

Example: Picture the Lo and Hi settings on a stove. The higher the setting, the faster your food cooks. Too hot, too quickly, and there goes your dinner. It is all about finding the right temperature.

Lines per inch or interval (mm)

LPI is the number of laser passes made per inch during engraving. Interval is the physical spacing between lines. They have an inverse relationship: as LPI goes up, the interval goes down. They are two ways of measuring the same thing, which is line density and resolution. LPI tends to be easier to use and understand.

A higher LPI gives finer detail and a smoother engrave, because the passes cover the surface more densely. A lower LPI gives a coarser engrave with less detail, suited to faster jobs or larger designs.

Example: Imagine painting a room. As you swipe left to right, you overlap the previous pass to get full coverage. Stay in one spot too long, though, and the area becomes oversaturated.

Focal depth (mm)

Focal depth, also called focal length or focus distance, is the distance between the laser lens and the surface of the material. It sets where the beam converges to its smallest point, the focal point, which decides the resolution you can achieve and how much heat is concentrated in one spot.

With the correct focal depth, the beam is focused exactly on the surface and the engrave is at its best. With the wrong focal depth, the engrave can be blurred or distorted, because the beam converges above or below the surface.

There is a use for defocusing slightly, by 2 mm or less up or down. It is common when ablating powder coating from a metal cup. The dot gets larger out of focus, which helps smooth the edges of the engrave on coated metal, a less forgiving material. It is also useful when cutting thick material: placing the focal point inside the material transfers more power and makes cutting easier.

The shorter the focal distance of a lens, the smaller the dot and the more pulses fit into a small area, which suits fine detail engraving. The longer the focal distance, the larger the dot and the wider the power is spread, which suits cutting thicker material.

Example: Remember holding a magnifying glass up to the sun as a kid? Held at just the right distance from a pile of leaves, it concentrates the sunlight into a point small enough to start a fire. That intense spot is the focal point, and the distance from the glass to the leaves is the focal depth.

How to get the results you want

Different combinations of settings give different results, and changing just one can change the result completely. Test only one variable at a time. The settings also interact with each other, and understanding how is central to mastering the machine. It takes some trial and error to find what you like best.

Speed and power

Speed sets how quickly the laser traces an outline or scans a filled shape or image. Power sets how much energy the tube puts out. Together they decide how deep you go into the material.

Speed directly controls how long the material has to absorb heat. Slowing down gives it more time to burn, and speeding up gives it less. Raising the speed or lowering the power gives a shallower, lighter engrave or a shallow score. Lowering the speed or raising the power gives a deep, dark engrave, or a cut.

Arrays and wide format

High speeds are only useful over large areas, because of over-scanning. All the CO2 lasers we offer need space to overscan.

Example: A car has to travel a certain distance before it reaches top speed, and needs a certain distance to stop. The higher you set your fill speed, the more distance the laser head travels and the more space it needs to stop.

LPI or interval

Once you have the speed and power, fine-tune the result with the LPI. An LPI of 300 (0.085 mm) gives a fairly good level of detail. For more detail, try 400 (0.064 mm). For heat-sensitive materials, go lower, such as 200 (0.127 mm). Sometimes an LPI of 800 (0.032 mm) or more is needed for silky smooth edges.

Feathering

For heat-sensitive materials such as glassware and tumblers, spread the heat by taking the beam slightly out of focus. Lowering the bed 1 to 2 mm makes the spot larger and spreads the heat. It does reduce resolution, but in some cases it is the only way to keep a sensitive material from melting.

Focus at the core

For better cutting, focus the laser at the core of the material instead of at its surface. Focus as normal, then use the manual focus gauges and the Z Move function to raise the material closer to the laser head by a quarter to half of its thickness. This puts the most powerful part of the beam inside the material and keeps a larger area in focus for the cut. It is especially useful for thicker materials.

Engraving, ablating and etching

Start with a relatively quick speed (300 to 800 mm/s) and adjust the power until you reach the depth you want. A speed of 300 mm/s is usually a great place to start. Unless the item has a large area to engrave, a higher speed actually takes longer. If you are at maximum power and still not reaching the depth you want, lower the speed or raise the LPI.

Cutting

Cutting speed and power depend on the wattage of the tube. A NOVA 14 and a MIRA 9 have very different work areas, but with the same 100 W tube they will likely use the same general cutting settings.

• Thick materials (1/4” and above): a medium to high power of 60–90% and a low to medium cut speed of 5–20 mm/s is usually in the ballpark.
• Thinner materials (about 1/8” and below): start with a more conservative low to medium power of 30–60% and a medium to high cut speed of around 10–30 mm/s.

How fast can each tube wattage cut?

• 40 W tubes tend to cut best at the lower end of the speed range. Maximum cutting thickness is about 1/4”.
• 60 W tubes tend to cut best at the lower end of the speed range. Maximum cutting thickness is about 3/8”.
• 80 W to 100 W tubes will likely stay in the low to mid teens for speed. Maximum cutting thickness is about 1/2”.
• 130 W to 150 W tubes can go towards the upper end of the speed range. Maximum cutting thickness is about 5/8”.

In every case, use the power range given above for the thickness of the material.

Where the settings are in LightBurn

LightBurn has no shortage of settings. This guide covers the Cuts/Layers window, because that is where all the settings above are entered. For more, visit the LightBurn website or see LightBurn Basics.

Cuts/Layers window

The Cuts/Layers window organizes all the layers of a job and the order in which they run. Click a layer once to edit its main settings in the summary below. Double-click a layer to open the Cut Settings Editor, where you can edit the main and the more advanced settings.

Layers

A single job often uses several sets of settings. You might engrave to different depths, or engrave one part and cut out another. Layers let you assign different settings to different parts of the design, and decide how and in what order each one is handled.

The color palette at the bottom of the LightBurn window assigns a set of parameters to all or part of your design. Each color is its own layer, and you can program up to 30 unique layers. If layers become hard to tell apart, right-click the swatch in the Cuts/Layers window and the part of the drawing on that layer will blink.

Example: Imagine making a sandwich. Each layer goes on in a particular way and a particular order. Once all the layers are on, you can remove the crust or cut it in half.

Mode

Mode tells the laser whether to follow the outline of a shape (cut or score), sweep to fill the inside (engrave), or both.

• Line cuts or scores a vector graphic, which is an image made only of lines and curves.
• Fill engraves a vector graphic. Instead of outlining the image, it fills the space between the lines with parallel strokes.
• Offset Fill is like Fill, but follows the outer lines of the shape instead of using parallel lines. It is not suggested for a CO2 laser.

Speed (mm/s)

Speed sets how quickly the laser traces an outline or scans a filled shape or image.

Power Max (%)

The power the laser fires at once it reaches the speed set for that layer. When engraving in Fill mode, the laser head over-scans so that it reaches the set speed before the laser fires. When scoring or cutting, the speed naturally varies, and the power varies with it.

Power Min (%)

The power the laser fires at when it slows down for curves or corners on that layer. Generally, minimum and maximum power should be the same. A lower minimum power helps reduce uneven cut depths, because it adjusts the power to make up for changes in speed.

Example: When you drive a car, you adjust your speed often, slowing for bends and speeding up on straights. A laser is no different. Adjust the minimum power to suit the file.

Interval (mm)

The tighter the spacing, the higher the resolution, and the longer the job takes. LPI is in the advanced settings, which open when you double-click the layer.

Pass count

Pass Count sets how many times the design on the current layer is repeated. It is really only useful for deep engraves and cuts that need more than one pass. For best results, refocus the laser between passes.

Show and Output

Show chooses which layers are visible on screen. Output chooses which layers are sent to the laser. Output is helpful when a single design covers several types of material, and hiding layers helps when they start to overlap.

Summary

Getting great results comes from understanding your materials and your settings. Learn how a material is composed and how it behaves, then adjust speed, power, LPI and focal depth to suit it. With knowledge, experimentation and attention to detail, you can get the full potential out of your machine.