Which acrylic is best for my laser project?
Acrylic can be laser cut effectively with a suitable CO₂ laser. Choose cast acrylic when a clear, white engraving is important; extruded acrylic can be a good choice for cutting jobs where consistent sheet thickness matters. A clean cut edge also depends on your machine, the material specification and the settings. Start with a test piece before processing a whole sheet.
Acrylic, PMMA and plexiglass: what are you putting in the laser?
PMMA is the plastic usually referred to as acrylic or acrylic glass. Plexiglass is often used as a generic term; PLEXIGLAS® is a brand name. The name alone does not tell you how a sheet was manufactured or which coating it has.
Check the material description: is it PMMA, is it cast or extruded, and are any coatings and protective layers suitable for your process? A clear plastic sheet could also be polycarbonate or PETG. Those materials melt differently and have different requirements for fume extraction and machine compatibility. Never simply apply a PMMA profile to them.
Still deciding between plastic, wood and cardboard? Start with the material selection guide for laser cutting.
Choosing cast or extruded acrylic
Cast acrylic is often designated GS; extruded acrylic is designated XT. Both can be processed with a suitable CO₂ laser. The main differences concern engraving and thickness variation.
| Selection criterion | Cast acrylic (GS) | Extruded acrylic (XT) |
|---|---|---|
| Engraving | Usually a white, matt engraving with clear contrast | Usually less white contrast |
| Laser cutting | Suitable for smooth cut edges | Also suitable for smooth, glossy cut edges |
| Sheet thickness | Can vary more; measure for fitted joints | Generally more consistent; measurement is still necessary |
| Practical choice | Nameplates, engraved labels and visible parts | Cut parts where engraving contrast is less important |
The differences are also described in the Trotec material guide. They are not a guarantee for a particular sheet or machine.
For example, make a GS test piece first for a table sign with an engraved name. For an unprinted divider, compare GS and XT for dimensional accuracy and cutting results. Do not base your choice solely on the assumption that one production method always gives the best edge.
Which laser can cut acrylic?
CO₂ laser: suitable for many PMMA variants
A CO₂ laser is the usual choice for cutting and engraving acrylic. The maximum usable thickness varies by machine. Cutting through a sheet is also different from achieving adequate dimensional accuracy and edge quality. Check the material and machine combination against both manufacturers’ documentation. The PLEXIGLAS processing guide also emphasises that quality depends on factors including the variant, thickness and colour.
Blue diode laser: colour and pigment are decisive
A typical blue diode laser cannot reliably cut directly through clear, colourless acrylic: the material does not absorb enough of this light. Some dark, opaque variants can be processed, but the pigments and the specific machine determine the result. The word “black” on a label alone is not proof of compatibility. xTool explains this limitation for its blue diode laser.
A coating that enables surface marking does not prove that you can also cut through the sheet. Explicitly check whether the material can be cut with your model.
Fibre laser: not the standard choice for acrylic sheet
A typical fibre laser marker for metal does not replace a CO₂ cutting laser. Marking plastic and cutting through plastic sheet are different applications. Check the manufacturer’s list of materials and processes; Epilog distinguishes between CO₂ and fibre applications.
Choose appearance and thickness to suit the design
For a clear window or a sign that you want to engrave from the back, clear cast acrylic is a logical starting point. For a white background for lettering or a display, consider white acrylic . For a lightbox, pay particular attention to light transmission and diffusion: white does not automatically mean opal.
Matt, tinted and mirrored variants give a different appearance. With mirrored acrylic, the backing must also be suitable for your process. Do not transfer settings for clear PMMA to a special-effect sheet without testing.
There is no universally ideal sheet thickness. A small hanging label has different requirements from a freestanding display. Choose according to dimensions, support, load and available machine capacity. Thicker material also requires more attention to the cut and fit.
A sheet sold as 3 mm may not measure exactly 3.00 mm everywhere. Measure at several points with callipers when parts need to fit into slots. Cut a small fitting test first and assess it after cooling. For mating parts, read about kerf and tolerances in laser cutting.
Prepare the sheet, machine and workspace
Only work with materials whose composition you know. Check the product specification and, where necessary, the safety data sheet, including coatings and films. If anything is unclear, consult the supplier before using the laser.
PVC, PVC-based vinyl and other chlorine-containing materials must not be put in the laser: they can release harmful, corrosive fumes. Even a thin unidentified film is not a harmless addition. Epilog describes the risks to the machine from substances such as hydrogen chloride.
Check extraction, filters and air supply according to the machine manual. Air assist does not replace extraction. Remove combustible cutting waste, lay the sheet flat and use a suitable cutting support. Supervise the process continuously: acrylic and the vapours released can ignite. If flames persist, stop using the procedure specified for your machine.
Only leave protective film in place if the supplier confirms it is suitable for the process. For engraving, you may need to remove it on the engraving side. Test its effect on residue and detail; do not replace an unidentified film with arbitrary tape. The guide on leaving or removing protective film can help you decide.
Use a small, documented test matrix
Settings are not a fixed property of a material. Power, speed, focus, lens, air assist, machine condition, material batch and thickness all interact. A power percentage from another machine is therefore not a directly transferable recipe.
Use the following procedure to assess your process:
- Choose a documented starting profile. Start with the machine manufacturer’s recommendation for the PMMA variant and thickness concerned.
- Create a representative test design. Combine an outer contour, a small hole, a corner and, where needed, an engraving or fitted joint.
- Vary settings in a controlled way. Test a few combinations of speed and power within the permitted limits. Initially keep the focus, support and other settings unchanged.
- Assess after cooling. Check that the cut goes all the way through, and inspect the top and bottom edges, dimensions, engraving contrast and deformation. Do not force a part free if it is still attached.
- Record the result. Record the material, batch, measured thickness, machine, lens and settings alongside a photo. Repeat the check for a new batch or a changed setup.
For a series of nameplates, a miniature version of the actual design is more useful than a straight cut alone. Small letters, holes and corners can reveal problems that are barely visible on a long straight edge.
Assessing cut edges and troubleshooting
A glossy edge can still have small ridges or an angular deviation. Check that the part fits and that the visible face is free of deposits. Look for the cause of a problem before increasing the power.
| What do you see? | What can you check? |
|---|---|
| The part is not fully cut free | Material suitability, actual thickness, focus, clean optics and an appropriate machine profile |
| Dull or milky cut edge | Air assist and the interaction between speed and heat input |
| Local marks on the underside | Contact with the cutting support, contamination and reflections from the bed |
| Deformed small details | Duplicate cutting lines and heat build-up between closely spaced contours |
| Haze around the engraving | Extraction, protective film, deposited residue and the engraving profile |
With acrylic, excessive airflow can make the edge more matt. Follow the machine instructions when adjusting it; do not simply switch air assist off for more gloss. Trotec describes the relationship between air supply, edge quality and extraction. Extraction and fire control remain the priorities.
When troubleshooting, change one factor at a time. A second cutting pass is not an automatic solution: first check why the first cut was inadequate and what the manufacturer recommends for that situation.
Engraving without unwanted haze
Distinguish between the intended matt engraving and an unwanted haze around it. That haze may be surface residue, but it can also be damage to the surface. Increasing engraving power is not necessarily the solution.
Use a test piece with text, thin lines and a filled area. Check each element separately. A setting that fills an area well may make small lettering less sharp. Use the same material type when comparing engravings.
For clear signs, consider engraving the back. Mirror the text and image in the design so that they read correctly from the front. Make a small sample first to assess contrast, orientation and the effect of the background.
Cleaning, finishing and bonding
Let parts cool and observe the specified extraction time before removing them. Carefully remove the film. Clean with a soft cloth and a cleaner suitable for that acrylic. Do not rub dusty surfaces dry or use an arbitrary solvent; see the PLEXIGLAS cleaning recommendations.
A visible cut edge does not always need additional polishing. Finishing changes the surface and may alter the dimensions. First assess whether the edge meets the requirements of the application.
If you intend to bond parts, make a separate joint test piece. Laser cutting can introduce stress at the edge; contact with certain adhesives or solvents can then cause stress cracking. The PLEXIGLAS processing guide covers this relationship. Follow the instructions for the sheet and adhesive, including any required stress relief. A clear edge alone does not prove that it is ready for bonding.
From test piece to the right sheet
Before producing a series, record the required variant, thickness and finish, and which test you have approved. Then compare the acrylic range against those requirements. Check the available sizes and product specifications for the chosen variant so that your design, material and laser setup work together.