Fabrication guide Laser-cut edges
Laser cutting does not leave the same edge on cast and extruded acrylic. Cast is the sheet whose cut edge can be polished into a show edge. Extruded is the sheet whose cut edge is usually left frosted, or polished only if that member is not the look. Choose the route from the edge the customer will see, not from the word “laser.”
The short answer
Decision rule. If the laser-cut edge faces the customer and should read as clear, start with cell-cast acrylic and name the polish. If the edge is hidden, or a frosted cut is acceptable, extruded acrylic is usually enough. The laser is the cutting method. It is not the specification.
What the laser actually leaves
A CO2 laser cuts acrylic by melting and vaporizing a kerf. The edge you get depends on the sheet route, the thickness, the speed, and whether anyone polishes it afterward. “Laser-cut” only means the outline was cut that way. It does not mean the edge is glossy, square, or ready for a show face.
Cast sheet — the process in ISO 7823-1 — is what display shops cut when the edge will be finished. Extruded sheet — ISO 7823-2 — cuts cleanly as an outline and typically leaves a frosted edge. That frost is normal. It is not a failed cut.
Cast edge vs extruded edge
Directional. Machine settings and thickness move the result. This is not a lab table.
| Cell-cast | Extruded | |
|---|---|---|
| Edge as cut | Can come off the laser closer to a finishable edge | Typically frosted |
| After polish | The usual clear show edge on a cube | Can be improved; still not the same as cast |
| Best role | Customer-facing outline, polished | Hidden outline, or an edge that may stay matte |
| What a photo hides | Whether the polish was flame or diamond | Whether anyone polished it at all |
Do not write “glass-like laser edge” into a purchase order. Without the route and the polish method, that phrase describes a hope.
Polish after the cut
The cut and the finish are two steps.
- As-cut. Acceptable on a hidden edge, a jig, or a part no one handles as a jewel face.
- Flame polish. Faster. It clears a cast edge for many retail parts. It is not the same as a diamond polish, and it can round a sharp detail.
- Diamond or mechanical polish. The clearer, more controlled show edge. More time. The finish to name when the edge is the product.
Specifying flame on an extruded edge, or diamond on a member that is hidden, is how the edge cost and the edge result get out of line. Match the finish to the route and to who sees it.
Which sheet for which edge
Polished cube or lid rim
Cast, then a named polish. This is the edge the brand is paying for.
Internal divider
Extruded, as-cut or lightly finished. The edge is not the camera face.
Flat sign with a visible outline
Cast if the outline must read clear. Extruded if a frosted outline is acceptable and cost matters.
Slotted part
Extruded helps the fit. If that same edge is also a show edge, you are in a compromise — say which matters.
Parts where the edge is the decision: boxes, trays, and display stands.
What to write on the RFQ
- PMMA, cast or extruded, on the members that are laser-cut.
- Edge condition: as-cut, flame polished, or diamond polished — and on which edges.
- Which edges face the customer.
- That a frosted extruded edge is accepted, if it is.
A quote that says only “laser-cut acrylic” has not answered this page. Ask before you compare price.
Sanait fabricates acrylic displays and treats the edge as part of the brief. How a brief is taken is on the FAQ. Scope is on the about page.
FAQ
Should laser-cut display edges be cast or extruded?
Cast if the edge faces the customer and should be clear. Extruded if the edge is hidden or a frosted cut is acceptable.
Why is my extruded laser edge cloudy?
That is the normal as-cut result on extruded sheet. It is not, by itself, a bad cut. A clear edge on that member means a polish, or a move to cast.
Does laser cutting polish the edge?
No. The laser cuts. Polish is a later step, and flame and diamond are different steps.
Can I polish an extruded laser edge until it matches cast?
You can improve it. You should not expect the same show edge as polished cast. If the match matters, specify cast on that member.
Is a frosted edge a defect?
Only if the drawing asked for a polished or clear edge. On a hidden extruded member it is the expected condition.
What if two quotes both say laser-cut?
Align route and edge finish before you read the price. One may be extruded as-cut. The other may be cast and diamond polished.
Sources
The two sheet routes are defined by the standards below. They do not define a laser-edge gloss value.
- ISO 7823-1:2003, Plastics — Poly(methyl methacrylate) sheets — Part 1: Cast sheets. iso.org
- ISO 7823-2:2003, Plastics — Poly(methyl methacrylate) sheets — Part 2: Extruded sheets. iso.org
- “Poly(methyl methacrylate).” Wikipedia. en.wikipedia.org
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