Short conclusion
For flat acrylic profiles, letters, slots, and light engraving, a CO2 laser is usually the faster and cleaner first choice. The beam cuts without touching the sheet, and on cast PMMA it often leaves a glossy edge that needs little extra polishing.
For pockets, steps, thick blocks, controlled hole diameters, and inside corners that must match a tool radius, CNC routing is the more predictable process. The cut edge is machined, not flame-polished, so optical edges still need a separate polish if the part is a display face.
Many retail fixtures use both: laser-cut panels and CNC-machined blocks or pockets. The process should follow the feature, not a blanket rule that one method is always more precise.
What each process actually does
Acrylic in this article means poly(methyl methacrylate), PMMA, in cast sheet, extruded sheet, or block. Cutting method does not change the polymer grade. It changes heat input, edge texture, and which geometry is practical.
Laser cutting
A CO2 laser, commonly at a wavelength of 10.6 micrometers, heats a narrow path until the acrylic vaporizes. The head does not touch the sheet. Assist air blows vapor and molten residue out of the kerf. The same machine can engrave a shallow mark by lowering power or raising speed.
Typical shop work is 2D profile cutting from about 1.5 mm to roughly 20 mm. Thicker plate can be cut, but cycle time, taper, and heat staining rise quickly. Inside corners come out nearly sharp because the beam width is small, though the kerf is still a real width, not a zero-width line.
CNC cutting
A CNC router or mill removes chips with a rotating bit. The tool has a diameter, so every inside corner has a radius of at least half that diameter unless a later operation clears it. The process can cut the outline, drill and bore holes, and machine pockets or 3D contours in one setup if the fixture holds the part.
CNC is the usual route once the part is a block rather than a sheet profile, or when a pocket depth and a hole size are both on the drawing.
Structured comparison
| Question | CO2 laser cutting | CNC routing or milling |
|---|---|---|
| Contact | None. Heat and gas flow do the cutting. | Tool contact. Fixtures and tabs or tape are required. |
| Best geometry | Profiles, slots, lettering, light engraving. | Pockets, steps, bores, contours, thick blocks. |
| As-cut edge | Often glossy on cast sheet. Can show a slight taper or heat line. | Matte tool marks. Clear only after flame, vapor, or diamond polishing. |
| Inside corner | Limited by kerf, often well under 0.5 mm wide in thin sheet. | Limited by tool radius. A 6 mm bit leaves a 3 mm radius. |
| Feature tolerance | Often held around 0.1 to 0.3 mm on sheet profiles if focus and sheet flatness are controlled. Not a substitute for a bored hole callout. | Holes and pockets can be held tighter when the drawing, tool, and fixture support it. Sheet thickness still follows the mill tolerance. |
| Heat effects | Narrow heat-affected zone. Extruded sheet is more prone to melt lips and later crazing. | Friction heat if feed is low or chips recut. Air blast or proper chip load limits melting. |
| Setup speed | Fast for nested flat parts and one-off profiles. | Slower setup, better when depth features repeat. |
| Poor fit | Deep pockets, threads, optical faces that must stay flat, parts that already carry high internal stress. | Very fine openwork in thin sheet, where a laser is faster and leaves less tooling mark. |
These ranges describe ordinary acrylic display work on cast or extruded sheet. They are not inspection limits. Quote the drawing tolerance, the sheet grade, and the edge spec instead of a machine slogan.
Parameters that change the result
Published laser speeds are not transferable between shops. Power, focal length, nozzle gap, and whether the sheet is cast or extruded all move the result. What can be specified is the outcome.
Kerf: often about 0.15 to 0.4 mm on common CO2 optics in sheet under 10 mm. It widens with thickness and with a longer focal length. Nesting software should offset the path by the measured kerf, not a catalog default.
Focus: a focus set at or slightly into the sheet reduces bottom taper. A focus error shows up as a rounded top edge or a wider bottom.
Speed and power: too slow leaves a heavy melt lip and yellowing. Too fast leaves a striated, incomplete cut. The useful window is found on a coupon of the same batch.
CNC tool diameter: state the largest inside radius you can accept. If the drawing shows a sharp corner, the shop must either use a smaller tool or note the remaining radius.
Chip load: acrylic prefers a steady cut over rubbing. Dwelling in a corner melts the wall. Climb versus conventional cut changes edge haze on some tools.
Holding: vacuum or tape on sheet; clamps clear of the toolpath on block. A loose part will chip or show a tapered wall even if the program is correct.
Cast sheet versus extruded sheet
Process choice and sheet type interact. Cast PMMA generally laser-cuts with a cleaner polished edge and engraves with a whiter frost. Extruded PMMA is more consistent in thickness and often cheaper, but it softens into a lip more easily and can craze later if solvent, stress, and a laser edge meet.
Thickness is a separate limit from cutting accuracy. ISO 7823-1:2003 sets requirements for non-modified flat cast PMMA sheet and covers a thickness range of 1.5 mm to 25 mm. Extruded sheet is a different part of the same series. Thickness tolerance depends on process and nominal thickness, so a profile held to 0.2 mm can still sit on a sheet whose thickness varies by more than that. For a press fit or a stacked display, call out both the cut size and the thickness range, and ask for the batch certificate.
Optical quality also differs by grade. A general-purpose sheet and a higher-clarity grade can share the same cutting program and not look the same in a cosmetic case. Do not treat light transmission or hardness numbers from an unnamed data sheet as guaranteed for every clear sheet.
Which process fits which part
Laser is the default
Flat letters, logos, and shelf talkers where the edge is visible and a glossy cut is acceptable.
Nested panels, slots, and finger joints in 3 to 8 mm sheet.
Engraved marks, lightly frosted windows, and part numbers that do not need paint.
Openwork patterns in thin sheet, where tool radius would close the gaps.
CNC is the default
Blocks and risers with pockets, recesses, or stepped heights.
Holes that must fit a pin, magnet, or standoff, especially if the drawing states a limit.
Parts thicker than the shop laser handles cleanly, or parts where a heat line on the edge is rejected.
Contoured edges and chamfers that a beam cannot machine as a controlled angle.
Use both
A typical display box may use laser-cut walls and a CNC-pocketed base. A sign may be laser-cut, then CNC-drilled for standoffs if the hole size is critical. Splitting the work is normal. It is not a sign that the first process failed.
For related design limits on radii, bends, and polished edges, see Can Acrylic Products Be Made in Any Shape?. Cut blanks for displays and blocks are grouped under acrylic cutting and engraving and custom acrylic blocks.
Edge finish after cutting
A laser edge on cast sheet is often clear enough for a side view of a brochure holder or a letter. It is still a heat edge. Expect a faint line, slight taper through thick plate, and occasional witness marks where the cut starts.
A CNC edge is geometrically easier to control and optically dull until it is finished. Flame polishing restores gloss on simple outside edges but can round a sharp arris and add stress. Diamond polishing is slower and is the usual choice when the edge is a viewing face. Vapor polishing reaches internal features a flame cannot, with its own effect on fine detail.
State the finish in words: as-cut laser, machined, flame polished, or diamond polished. A note that only says clear is not an edge specification.
What to put on the drawing
Material: cast or extruded PMMA, color, and thickness, plus whether thickness is nominal or a checked range.
Which faces are seen, and the edge process allowed on those faces.
Critical sizes only. Over-tolerancing every profile raises cost without changing the display.
Inside radii, or a note that laser kerf or a named tool radius is acceptable.
Hole function: clearance, press, or threaded insert. Acrylic threads in the plastic itself are a weak default.
Engraving depth as a visual target, not an unchecked 0.01 mm depth, unless the mark is functional.
Masking: keep the protective film on through cutting if the face must stay unscratched.
FAQ
Is laser cutting more accurate than CNC on acrylic?
Not as a general rule. Lasers are accurate on flat profiles when kerf is measured and the sheet is flat. CNC is usually better when the important sizes are hole diameters, pocket depths, or features on a thick block. Sheet thickness tolerance can dwarf either cutting error.
Does laser cutting seal or strengthen acrylic?
No. It vaporizes a path and may leave a glossy edge. It does not improve impact performance. A poor laser setup can add stress that shows up later as crazing, especially on extruded sheet near solvents or tight bends.
Why do some laser-cut edges look yellow or ridged?
Speed, power, focus, or airflow is off for that thickness, or the sheet is a grade that melts instead of vaporizing cleanly. Extruded sheet and recycled-content sheet do this more often. A same-batch coupon is the practical check.
Can CNC match a polished laser edge?
Not in the cutting pass. The machined face needs flame, diamond, or vapor polishing. After polishing, a CNC edge can look as clear as a laser edge, sometimes straighter on thick parts.
What thickness is too much for a laser?
There is no single cutoff. Many display shops stay with laser profiles up to about 12 to 20 mm and move thicker plate or deep pockets to CNC. The limit is edge taper, cycle time, and the machine on the floor, not a property of PMMA.
Are the fumes only an odor issue?
No. Laser cutting PMMA releases vapor that should be extracted and filtered. Shops treat this as a ventilation requirement, not a cosmetic one. Mechanical routing also needs chip and dust collection.
Author and factory context
Who runs sk-display.com. SK Display Co., Ltd. is a custom acrylic display and fabrication factory in Dongguan, Guangdong, China. The site is sk-display.com. Work is wholesale and made to order, not retail stock. Public company background is on the about page. Cutting examples sit in acrylic cutting and engraving. Enquiries go through contact.
In that shop, flat display panels, holders, and engraved marks are usually laser-cut. Pockets, thick blocks, and holes with a stated fit are usually CNC-cut, then polished only where the edge is in view. Sample lead time is often a few working days. Production timing depends on finish, quantity, and whether bonding or printing follows the cut.
Sources
ISO 7823-1:2003, Plastics - Poly(methyl methacrylate) sheets - Types, dimensions and characteristics - Part 1: Cast sheets. Scope includes non-modified flat cast PMMA sheet from 1.5 mm to 25 mm. Thickness and other characteristics are grade-dependent. ISO 7823-1:2003.
PubChem record for poly(methyl methacrylate), used here only to identify the polymer. PubChem PMMA.
OSHA laser hazards overview, for the point that laser work is an exposure-control issue, not only a cut-quality issue. OSHA laser hazards.
No competitor fabrication sites are cited. Shop ranges in the table are practice notes from display work, not values copied from a certified test report.