Acrylic CNC Machining

DEK's acrylic CNC machining turns cast and extruded PMMA into optically clear parts with ±0.01 mm on critical features and prototypes in 3–5 days. Sharp tooling, air-blast cooling and a polishing route restore full transparency.

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±0.01 mm
Critical Features
3–5 days
Prototype Lead Time
92%
Light Transmission

Clear acrylic machined parts with holes and features

ISO 9001:2015 Certified AS9100D and ISO 13485 certified

Why Acrylic Machining Needs a Careful Shop

Acrylic punishes shops that cut it like aluminum: it crazes, chips and clouds under heat, clamping pressure or the wrong coolant. PMMA is one of the materials covered by our plastic CNC machining services, run on the same 3-, 4- and 5-axis mills as your metal parts.

Because acrylic parts usually mount into metal housings, we machine the aluminum or stainless companion parts in the same order and check the fit before both ship. Browse the full range under CNC machining plastics.

ISO 9001:2015, ISO 13485 and AS9100D
Engineer-reviewed pricing within 6 hours
No MOQ, from 1 to 10,000+ pieces
IQC, IPQC, FAI and OQC on CMM

Three clear machined acrylic parts on dark surface

Acrylic Grades We Machine

Cast PMMA: 1.19 g/cm³, 65–75 MPa tensile strength, 80 °C max service. Specify cast if the part is polished, bonded or over 12 mm thick.

Cast acrylic (PMMA-C)
92% light transmission
Higher molecular weight, lower internal stress. The default for optical parts, thick blocks and anything that will be polished or bonded.
Extruded acrylic
Lower cost, tighter thickness
PMMA-E is softer, gummier at the cutter and more prone to crazing. Good for flat covers and simple cut-outs at stock thickness.
Impact-modified acrylic
Added toughness
For guards and handled components that take knocks, at a small cost in clarity compared with standard cast sheet.
UV-filtering grades
UV-transmitting or filtering
UV-transmitting and UV-filtering grades for instrument windows and photo-curing fixtures that must control the light passing through.
Mirrored sheet
Colored, frosted, mirrored
Colored, frosted and mirrored sheet for display and signage parts where appearance matters more than optical clarity.
Cast PMMA (typical)
~70 × 10⁻⁶/K expansion
Three times aluminum's expansion, 0.3% water absorption in 24 h and 80 °C service (extruded grades about 70 °C). Plan clearances accordingly.

CNC mill cutting clear acrylic manifold with internal channels

±0.01 mm
Small rigid features
±0.05 mm
Thin or large sheet parts
Ra 0.2 µm
Polished acrylic faces
Ra 0.8–1.6
As-machined finish (µm)

Acrylic CNC Machining Processes

In clear acrylic machining, PMMA machining tolerances are measured after 24 hours at room temperature, with haze and edge clarity checked too.

1

CNC Milling

3-, 4- and 5-axis CNC milling for pockets, windows, chamfered edges, engraved text and freeform lens surfaces, using sharp polished-flute tooling.
2

CNC Turning

Round lenses, sight glasses, light pipes and threaded caps turned with air-blast cooling to avoid heat that clouds or crazes the surface.
3

Drilling and Tapping

Peck cycles and reduced feed at breakthrough stop chip-out; threaded inserts go into holes that see repeated assembly instead of interference fits.
4

Polishing and Bonding

Flame, vapor and diamond polishing, laser marking and solvent bonding. For sheet enclosures, see custom acrylic fabrication.

Design & Machining Tips for Acrylic

Rules our engineers apply to keep custom acrylic parts free of cracks, crazing and fit problems.

1

Stress Relief by Annealing

We anneal cast blanks at about 80 °C with a slow cool before finish passes, and again before solvent bonding or exposure to alcohols, which otherwise craze edges.
2

Thermal Expansion

A 70 mm acrylic lens grows about 0.13 mm more than its aluminum barrel over a 40 °C swing. Leave radial clearance or use a compliant retaining ring.
3

Sharp Corners

Internal corners start cracks: specify a radius of at least 0.5 mm (1 mm preferred). External edges get a 0.3 mm chamfer unless they are flame polished.
4

Thin Walls

Keep walls at 1.5 mm or more, 2 mm where the part will be polished or bonded. We can hold 0.8 mm on short spans with a backing fixture.
5

Cracking and Crazing

Air blast or a non-aromatic coolant, low clamping pressure on soft jaws or vacuum fixtures, and no press-fit pins. Specify tapped inserts, not interference fits.
6

Holes and Optical Faces

Zero-rake plastic drills, 0.05 mm oversize for through-fasteners, countersunk heads. On optical faces, call out flatness and scratch-dig, not a linear dimension.

When to Choose Acrylic vs Polycarbonate or PET

How acrylic compares with polycarbonate and PET. If no transparent window is needed, aluminum machining holds tighter tolerances.

Criteria	This MaterialAcrylic	Polycarbonate	PET
Choose it for	Lenses, light guides	Guards, visors	Chemical exposure
Light transmission	92%	88%	–
Impact strength	Lower	10–20× acrylic	–
Polishability	Best	Lower	Lower
Scratch / UV	Resistant, UV stable	Less resistant	–
Food contact	–	–	Approvals

Where Custom Acrylic Parts Are Used

From microfluidic manifolds to cabin lighting lenses, machined PMMA serves wherever a part must be clear, light and precise.

Finishing Options for Polished Acrylic Parts

CNC machining plus finish: restore optical clarity, frost a diffuser face or mark part numbers on your acrylic parts.

Acrylic Finishes

Need another finish on PMMA? See all finishing options

Acrylic Machining FAQ

Common questions from engineers specifying machined PMMA parts.

Can acrylic be CNC machined without cracking?

Yes, when the shop controls heat and stress. We use sharp polished-flute cutters, air or compatible coolant, low clamping force, annealing before finish passes, and radii on internal corners. Crazing almost always traces back to skipped annealing or solvent exposure of a stressed part.

Should I specify cast or extruded acrylic for machining?

Cast for anything optical, thick, polished or bonded; it machines cleaner and holds less internal stress. Extruded for thin, flat, low-cost covers where stock thickness is used as-is.

How do you polish machined acrylic?

Flame polishing for straight edges, diamond or buff polishing for flat faces, and vapor polishing for complex or internal surfaces. Polished acrylic returns to 90%+ light transmission with Ra 0.2 µm or better.

What tolerance is realistic for acrylic CNC machining?

±0.01 mm on small rigid features, ±0.05 mm on large sheet parts. Thermal expansion is three times that of aluminum, so we inspect at 20 °C and recommend clearance in metal-to-acrylic fits.