Cast vs Extruded Acrylic: Which Is Better for Laser Cutting?
Cast acrylic is better for engraving because it frosts to a bright white; extruded acrylic is cheaper, has a more consistent thickness and glue-joins easily, and cuts with a glossy edge. Both cut well on a CO2 laser. Choose cast for signs and awards, extruded for cut-only parts and boxes.
You hold two sheets of 3 mm clear acrylic. Both look identical, both are protected by the same blue-grey film. One comes out of the laser with a snowy, high-contrast engraving; the other gives a pale, whispery mark. That is the story of cast versus extruded.
Cast acrylic is PMMA made by pouring liquid monomer between glass plates and letting it polymerise. Extruded acrylic is PMMA melted and pushed through a die in a continuous sheet. The longer polymer chains in cast sheet and the stress left in extruded sheet change how each reacts to a laser.
Side-by-side comparison
| Property | Cast | Extruded |
|---|---|---|
| Engraving | Frosty white, strong contrast | Clearer, lower contrast |
| Cut edge | Clean, may look slightly frosted | Often glossier, flame-polished |
| Thickness tolerance | Looser (sheet can vary) | Tighter, more uniform |
| Internal stress | Low | Higher, can craze with solvents |
| Solvent gluing | Works, slower | Works very well |
| Heat bending | Needs higher temperature | Bends at lower temperature |
| Typical price | Higher | Lower |
| Common brand clues | "GS" in Plexiglas naming | "XT" in Plexiglas naming |
Treat the table as general tendencies; manufacturers vary, and settings must be tested on scrap.
Factors that decide which to buy
- Do you engrave? Choose cast. Engraving on extruded often looks weak.
- Do you glue boxes or displays? Extruded; its edges weld smoothly with solvent cement.
- Does the part need exact thickness? Extruded for slots and press fits, because tolerance is tighter.
- Budget? Extruded is usually cheaper for big production runs.
- Will it be bent? Extruded is easier to heat-bend.
Worked example
A maker produces 20 keychains with a logo engraved plus a 30 mm cut outline, from 3 mm clear acrylic. On cast sheet, the logo reads white and sharp, and the outline cut stays almost clear. On extruded sheet, the logo reads dull. The maker picks cast for the keychains, but buys extruded for a stack of simple coasters, where the cut edge alone is the feature. Same laser, same speed; the sheet type changed the result.
Common mistake: setting the same speed and power for cast and extruded sheets. Extruded melts at a lower temperature and often needs slightly less heat for a clean edge. Test each sheet type separately.
Settings and checks
On a CO2 laser, both cut 3 mm at about 6-10 mm/s on 40 W at 70-90%, as a typical starting range; test on scrap. For the full guide see laser cutting acrylic. If you only own a diode laser, can a diode laser cut acrylic explains why neither type of clear acrylic will cut.
Pro tip: ask the seller whether the sheet is "cast" or "extruded". If the listing does not say, a cheap price and very uniform thickness point toward extruded; engrave a corner and look at the frost.
Not sure about the material? Read what materials can you laser cut before you buy.
How to test an unknown sheet
If a sheet has no label, do a two-minute test before you commit to a project.
| Test | Cast usually | Extruded usually |
|---|---|---|
| Engrave a 10 mm square at low power | Bright frosty white | Pale grey, translucent |
| Cut a 20 mm square | Clean edge, may look slightly milky | Glossy, clear edge |
| Measure thickness at 4 points | Varies by a few tenths of a mm | Nearly identical |
| Drop a little solvent cement on an offcut | Slow to soften | Softens and bonds quickly |
Run the tests on an offcut, not on the project. Combine the results with the supplier's description and you will usually know what you have.
Next step: order one small sheet of each, cut and engrave a 30 mm test square on both, and keep them on your workbench as a reference.
Questions and answers
Is cast or extruded acrylic better for laser engraving?
Cast. It frosts to a bright white that shows details clearly. Extruded engraving is paler.
Which acrylic cuts with a more polished edge?
Extruded usually gives a glossier flame-polished edge, though cast also cuts cleanly on CO2.
Is extruded acrylic cheaper?
Generally yes, and it often has more consistent thickness.
Can I mix cast and extruded in one project?
Yes, but settings and glue behaviour differ, so test each sheet and do not assume one setting fits both.
How can I tell cast from extruded?
Check the product label or datasheet. Names such as GS (cast) and XT (extruded) are used for Plexiglas, but many sheets are not labelled clearly.
Do both work with a diode laser?
Neither clear type cuts with a 445-455 nm diode; dark opaque acrylic may cut slowly.