Laser CNC Plastic Cutting Service: How to Pick One That Holds Tolerance
Laser cutting removes material with a focused beam, so the choice of machine, wavelength and assist gas decides whether your part comes off the bed clean or charred. This page is for design engineers and sourcing staff comparing shops. Read it and you will know which plastics belong on a laser, which belong on a mill, and what to ask before you release a PO.
In this article
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Key takeaways
Laser cutting vs CNC milling for plastic parts
Use this when a drawing could go either way.
| Criterion | Laser cutting | CNC milling |
|---|---|---|
| Best geometry | Flat sheet profiles, holes, slots | 3D pockets, threads, tight bosses |
| Edge finish | Polished or lightly re-melted, Ra 1.6–3.2 μm | Ra 0.8–1.6 μm, tool marks possible |
| Typical thickness | Up to about 12 mm per pass | Any thickness within travel |
| Hole aspect ratio | Roughly 1:1 thickness, less in thick stock | Deep holes with peck cycles |
| Tolerance on profile | ±0.1 to ±0.25 mm on sheet | ±0.005 mm where fixtured |
| Heat effect | Small heat-affected zone at the kerf | Mechanical, no char |
| Setup cost | Low, no dedicated fixture | Fixture and tooling time |
| Best fit | Prototype panels, covers, gaskets | Load-bearing and mating parts |
Supplier checklist by part type
Match the question to the part you are buying.
| Part type | What to ask | Red flag |
|---|---|---|
| Flat cover panel | Edge finish and flatness after cutting | No mention of extraction or assist gas |
| Gasket or spacer | Kerf compensation on the fit profile | Quote ignores kerf allowance |
| Drill jig | Hole position tolerance and datum | Profile tolerance quoted for holes |
| Medical housing | ISO 13485 and cleaning method | No traceability on material lot |
| Automotive bracket | IATF 16949 and PPAP support | Tolerance stated without units |
| Thick section part | Whether they will mill instead | Insists the laser is always best |
When to cut on the laser, when to mill
Pick the laser for flat thermoplastic profiles up to about 12 mm where edge polish and speed matter more than tight bores. Pick milling when the part has 3D features, filled or high-temperature polymer, or any callout at ±0.005 mm. Send the drawing and we will tell you which one your part needs.
What a laser actually does to a thermoplastic
A CO2 laser emits at 10.6 μm, which most thermoplastics absorb well. The beam melts and vaporizes a narrow kerf, and an air or nitrogen jet blows the melt out of the cut. There is no blade pressure, so thin sheet does not deform. That is the main reason a laser CNC plastic cutting service works well on 0.5 mm to 3 mm stock that would flex under a cutter.
The heat does not vanish. It spreads sideways into a heat-affected zone, usually 0.1 to 0.5 mm wide depending on speed and power. In PMMA and PC that zone re-solidifies glossy and is often acceptable as-is. In ABS, POM and PA you may see a pale re-melted lip that needs a light scrape or vapor wipe before the part looks right.
Thickness changes everything. A 3 mm acrylic sheet cuts at high speed with a clean edge. Push past roughly 12 mm and the kerf widens, the edge goes cloudy, and the bottom edge may show dross. At that point a mill is usually faster and cleaner, even though the laser can technically get through.
- 1Kerf widthTypically 0.1–0.3 mm; account for it in mating fits
- 2Heat-affected zone0.1–0.5 mm; visible as a color or gloss change
- 3Assist gasCompressed air for most plastics, nitrogen for oxidation-sensitive grades
Which plastics belong on the bed
Unfilled grades are the safe list. ABS, PC, PMMA, POM, PP, HDPE and PA all cut predictably with air assist and good extraction. PVC is the exception you should flag: it releases hydrogen chloride, which attacks optics and needs dedicated extraction. Many shops refuse PVC on a shared machine, and that refusal is a sign of a shop that knows its equipment.
Filled and high-temperature grades are the problem set. Glass-filled and carbon-filled nylon or POM cut badly because the filler does not vaporize; it leaves a rough, abrasive edge and the kerf wanders. PEEK and PEI need high power and slow speed, and the edge usually comes off brown. For those parts, 3-axis or 5-axis milling gives a far better result.
There is also a flatness question. Laser beds hold sheet flat by vacuum or by weights, but a warped sheet will cut out of focus and the kerf will vary along the path. If your stock arrives bowed, expect the shop to flatten it first or quote a mill instead.
- 1Clean cutsABS, PC, PMMA, POM, PP, HDPE, unfilled PA
- 2Cut with carePVC (extraction), thin PC (yellowing), foam-core sheet
- 3Move to millingGlass-filled, carbon-filled, PEEK, PEI, thick sections
What to send with the RFQ
Vector geometry is the starting point. DXF and DWG are the most reliable because the shop can read layer names, units and line weights directly. A high-resolution PDF or CDR also works if the curves stay clean. STEP and IGES files can be processed, but the shop has to extract the sheet profile from the solid, so add a note saying which face is the cut plane.
Say what the part does, not only what it looks like. A cover panel needs a good edge and a reasonable profile tolerance. A gasket or a spacer that sits between two mating faces needs a controlled kerf allowance. A drill jig needs hole positions tied to a datum. That one sentence changes how the shop nests and fixtures the job.
Finish and inspection scope belong in the same email. If edges must be vapor-polished, or holes must be reamed after cutting, list it. If you need a dimensional report, ask at quote stage, because adding it after the parts are cut means a second setup.
- 1Preferred.dxf or .dwg with units and layers set
- 2AcceptableHigh-resolution .pdf, .cdr, or .step with a cut-plane note
- 3Always includeMaterial grade, thickness, tolerance, finish, quantity
Holding tolerance on a laser bed
Profile tolerance on laser-cut plastic is not the same number as machined tolerance. On a well-set bed with flat stock, expect ±0.1 to ±0.25 mm on the outline. Hole position follows the same order. That is fine for panels, brackets and covers, and not fine for a bearing seat.
If a drawing calls for ±0.005 mm, that number comes from a machining center, not from the beam. Some features on the same part can be laser-cut and then finished on a mill: cut the rough profile on the bed, then skim a critical bore or slot to size. Splitting the work that way keeps cycle time low and still meets the tight callout.
Kerf allowance is the other half of the story. The beam removes 0.1 to 0.3 mm of material, so a nominal 10 mm slot will come out wider if the toolpath is not compensated. A shop that asks for your fit intent, not just your nominal dimensions, is compensating correctly.
- 1Sheet profile±0.1 to ±0.25 mm on flat stock
- 2Hole positionSame order as profile unless reamed after cutting
- 3Critical featuresSkim on a mill to reach ±0.005 mm
How to judge a laser CNC plastic cutting service
Start with the quote itself. A usable quote states material grade, thickness, tolerance, edge finish, inspection scope and lead time. A single number with no scope cannot be compared with another shop's number. Ask what is excluded: polishing, reaming, marking and reports are common add-ons.
Then ask what happens when the job is not a good laser fit. A shop that only runs a laser will cut your PEEK panel anyway and ship a brown edge. A shop with milling capacity will tell you to move the part to a 3-axis or 5-axis machine and quote it that way. That honesty saves a scrapped lot.
Certifications matter when your part feeds a regulated line. ISO 9001:2015 covers general quality systems, IATF 16949:2016 covers automotive, ISO 13485:2016 covers medical devices and ISO 27001:2022 covers information security. If your drawings are sensitive, ask for an NDA before you upload.
- 1Quote scopeMaterial, thickness, tolerance, finish, inspection, lead time
- 2Process honestyWill they move a bad-fit part to a mill?
- 3PaperworkISO 9001, IATF 16949, ISO 13485, ISO 27001, NDA on request
Step by step: from drawing to cut parts
- 11. Confirm the process fitsCheck material, thickness and feature size. Flat profiles up to about 12 mm and holes with roughly 1:1 aspect ratio suit the laser. Pockets, threads and 3D contours go to milling.
- 22. Send vector geometry with intentDXF or DWG with units set. Note the material grade, sheet thickness and which dimensions are critical. Add fit intent for any slot or hole that mates with another part.
- 33. Agree tolerance and finish in writingState profile tolerance (±0.1 to ±0.25 mm is realistic), edge finish, and whether holes need reaming. Ask for a dimensional report if the part is going into a regulated assembly.
- 44. Review the DFM note before cuttingA good shop returns a DFM analysis with the quote. Read it for kerf notes, minimum hole size and any warning about heat marks on your chosen grade.
- 55. Approve the first articleOn a new geometry, cut one part and check the critical dimensions and edge condition. Adjust power, speed or focus before the full run. This is cheaper than sorting a full lot.
- 66. Lock inspection scopeConfirm what is measured, what is recorded and what ships with the parts. Raw material check, in-process monitoring and final inspection are the baseline; add reports if your customer requires them.
Laser CNC plastic cutting questions
What file formats do you accept for laser cutting?
Vector files are best: DXF and DWG give the cleanest path, with units and layers set. High-resolution PDF and CDR files are also accepted.
STEP and IGES models can be processed, but we extract the sheet profile from the solid, so tell us which face is the cut plane.
Can you cut glass-filled or carbon-filled plastic?
It is possible but rarely worth it. The filler does not vaporize, so the edge comes out rough and the kerf can wander. Tool wear and cleanup add cost.
For filled grades we usually recommend milling the part instead. Send the drawing and we will say which route gives the better result.
How thick can you cut in one pass?
Most thermoplastics cut cleanly up to about 12 mm on a CO2 bed with the right assist gas. Beyond that the kerf widens and the lower edge can show dross.
On thick sections, milling usually wins on edge quality and cycle time. We quote both when the thickness is borderline.
Will the cut edge be polished?
It depends on the polymer. PMMA and PC re-solidify glossy at the kerf and often need no extra work. ABS, POM and PA can leave a light re-melted lip.
If your drawing calls for a specific edge appearance, say so at quote stage. Vapor polishing or a light wipe can be added as a separate operation.
What tolerance can you hold on laser-cut plastic?
On flat sheet with good stock, expect ±0.1 to ±0.25 mm on the profile and on hole position. That suits panels, covers, gaskets and spacers.
If a feature needs ±0.005 mm, we cut the profile on the laser and skim that feature on a machining center. The two operations run in one shop.
Do you sign an NDA before I upload drawings?
Yes. Uploads are treated as confidential and an NDA is available on request. Ask before you send the files and we will return a signed copy.
We also hold ISO 27001:2022 for information security, which covers how customer data is stored and accessed.
Send your plastic part drawing for a process check
Upload your DXF, DWG or STEP file and get a quotation with a free DFM analysis within 12 hours. No minimum order quantity, from one prototype to 10,000+ parts.
12-hour quote + DFMNo minimum order quantity100% inspection before shipmentNDA on request
More machining notes
We publish setup notes, tooling trials and inspection data from the factory floor.
