We machine PMMA on 127 CNC centers, from a single clear lens cover to 10,000-unit runs. Tolerances to ±0.005 mm, flame-polished edges, and full inspection before every shipment.
PMMA is soft, clear, and brittle at the same time. Four problems show up on almost every first run.
PMMA melts when the tool dwells. The heat leaves a white haze along the cut that no amount of hand polishing fully removes. Feed rate, spindle speed, and cutter geometry have to be matched to the sheet, not to a generic plastic recipe.
Cast acrylic is brittle under point loads. Clamping pressure that is fine on aluminum will craze a 6 mm panel before the first pass. We use soft jaws and low-pressure fixtures, and we check the sheet for pre-existing stress before it goes on the table.
Solvent vapors, thread-cutting oils, and paper masking left on too long all attack the surface. A part that measures perfectly can still fail visual inspection once it is bonded or cleaned. Masking type and removal timing matter as much as the cut.
Acrylic moves when the clamping force comes off. A 1.5 mm wall that reads true in the fixture can spring 0.1 mm once free. We rough, stress-relieve where needed, then take a light finishing pass to hold the dimension the drawing actually calls for.
Two capabilities carry most acrylic work: thermal control at the cutter, and edge finishing that does not distort the part.
Acrylic cuts cleanly when the chip leaves the flute before it reheats the wall. We run single-flute and two-flute cutters with high helix angles, air blast instead of flood coolant, and feed rates set by chip load rather than by spindle maximum. The goal is a chip that looks like a comma, not dust.
For deep pockets and thick sheet, we program trochoidal paths so the cutter engages a constant arc instead of a full-width bite. That keeps the temperature even along the profile and avoids the local melting that turns a clear edge opaque.
Machined acrylic has a matte edge unless you finish it. Flame polishing gives the clearest result on straight edges and simple curves, and it is fast. Vapor polishing reaches internal bores and tight radii that a torch cannot touch, but it needs tighter process control because the surface is being dissolved, not melted.
We pick the method from the drawing, not from habit. A light guide or a display window gets flame polishing. A fluid manifold with internal channels gets vapor polishing or a mechanical polish, depending on how much material removal the tolerance allows.
The two grades machine differently. Pick by the part, not by the price of the sheet.
| Property | Cast acrylic | Extruded acrylic |
|---|---|---|
| Machining behavior | Chips cleanly, less gumming | Softer, tends to smear at high rpm |
| Optical clarity | Higher, better for windows | Slight haze on thick sections |
| Thickness tolerance | Tighter across the sheet | More variation sheet to sheet |
| Best suited to | Optical parts, thick panels | Flat panels, simple profiles |
| Solvent bonding | Strong, predictable joints | Fast bonding, more stress risk |
| Cost | Higher per sheet | Lower per sheet |
PMMA is one material in a shop that machines metals and plastics on the same floor.
Flat panels, pockets, and profiles up to 4,000 mm. The workhorse for display windows, covers, and enclosures.
Rotary work for cylindrical lenses, tubes, and parts with features on more than one face.
16 simultaneous 5-axis centers for contoured optical surfaces and undercut geometry in one setup.
Mill-turn centers handle acrylic bushings, spacers, and insulator bodies with tight concentricity.
One-off clear parts for fit checks and design review, shipped before tooling is committed.
Flame polishing, vapor polishing, bead blasting, and laser engraving with a 1.5 mm minimum character height.
Numbers apply to PMMA and other engineering plastics unless noted.
| Item | Range | Notes |
|---|---|---|
| Achievable tolerance | ±0.005 mm | On critical features, with stable fixturing |
| Fine surface finish | Ra 0.2–0.8 μm | After polishing operations |
| As-machined finish | Ra 1.6–3.2 μm | Straight off the cutter |
| Maximum part size | 4,000 mm | Single axis, 4,000 × 400 × 150 mm |
| Rotary work | Ø400 mm | Table capacity on mill-turn centers |
| Sheet thickness | Typically 1–50 mm | Cast and extruded grades |
| Quality rate | 99.99% | Across inspected production |
Holding a number on acrylic is harder than on aluminum. We fixture soft, cut cool, and verify after the part is free of the vise.
Founded in 2011. The process knowledge comes from parts that failed early and were fixed, not from a material data sheet.
Milling, turning, and finishing in three wholly-owned plants covering 7,600 m². No brokering your job out.
Send a STEP file and a drawing. You get a quotation and a free DFM analysis within 12 hours.
Once the drawing is locked, production can start within 24 hours. Parts typically ship in 3–5 days.
Raw material check, in-process monitoring, and final inspection on every order. Reports on request.
Light guides and window covers need edge clarity and no internal stress marks, because any haze shows under backlight.
Instrument covers and fluid manifolds must be cleanable and dimensionally repeatable batch to batch, with traceable inspection.
Guard panels and inspection windows take impact and vibration. Acrylic gives the clarity without the weight of glass.
Interior light elements and sensor covers need color consistency and edge quality that survives bonding and aging.
Yes, with the right parameters. PMMA machines faster than most metals and leaves a good surface if the cutter stays cool and the chip clears. The failure mode is heat, not hardness.
It is a poor choice when the part needs high impact strength, continuous outdoor UV exposure without a coating, or operating temperatures above roughly 80 °C.
Clamping pressure and thermal growth are the two variables that matter most. We use soft jaws and low-pressure fixtures so the part is not distorted while it is being measured.
We also finish after releasing the vise where the geometry allows, and check critical dimensions with the part at rest rather than in the fixture.
As-machined, acrylic edges are matte. They look frosted and scatter light.
Flame polishing or vapor polishing restores clarity. The right method depends on geometry: flame for open external edges, vapor for internal bores and tight radii.
Both. Cast acrylic gives better optical clarity and holds thickness more consistently, so it suits optical parts and thick panels.
Extruded acrylic is cheaper and bonds quickly, but it smears more easily at high spindle speeds. Tell us the grade on the drawing and we program to it.
Up to 4,000 mm on the long axis, with a travel envelope of 4,000 × 400 × 150 mm on the large machines.
For parts beyond that, we can machine in sections and bond, but the joint will be visible in a clear part. Review that trade-off before committing.
Not from cutting forces, but it can craze from point loads and from pre-existing stress in the sheet. Cast acrylic sometimes arrives stressed from the supplier.
We inspect incoming sheet and adjust clamping when a batch shows stress. Sharp internal corners in the design are also a risk, so we add radii where the drawing allows.
Flame polishing, vapor polishing, mechanical polishing, bead blasting, and laser engraving. Laser marking has a 1.5 mm minimum character height.
As-machined surfaces sit at Ra 1.6–3.2 μm. Polished surfaces reach Ra 0.2–0.8 μm depending on geometry and access.
A STEP or IGES file plus a 2D drawing with tolerances and finish callouts. Tell us the acrylic grade if it is specified.
Quotation and a free DFM analysis come back within 12 hours. There is no minimum order quantity, so a single prototype is fine. Uploads stay confidential and we can sign an NDA on request.
Upload the STEP file and the 2D drawing. We return a price, a DFM review, and the finishing method we recommend for your geometry.
12-hour quote100% inspectionNo minimum order quantityNDA on request
Trusted by engineers and manufacturers worldwide
Upload your 3D model or 2D drawing and get a quotation with a free DFM analysis. Maximum processing size 4,000 mm.
CNC Metals 13 grades
CNC Plastics 10 grades
Machines & processes 12 options
Surface & post-processing 10 options
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