Acrylic CNC Machining Services
RpProto provides high-precision acrylic CNC machining services. As part of our plastic CNC machining capabilities, we deliver crystal-clear PMMA parts with tight tolerances and optical-grade surface finishes — for prototyping and low-volume production.
Achievable tolerance
Light transmittance
Certified quality
Our Capabilities
Our plastics-dedicated CNC machining centers run 3-axis and 5-axis machining configurations, minimising contamination risk from metal chips.
- Max part size (3-axis): 600 × 500 × 300 mm
- Max part size (5-axis): 500 × 400 × 250 mm
- Standard tolerance: ±0.05 mm
- Tight tolerance: ±0.02 mm
- Surface flatness: 0.03 mm / 100 mm
Acrylic / PMMA Material
PMMA is suitable for applications requiring the greatest accuracy and surface smoothness.
RpProto work with three primary grades.
| Property | Optical-Grade PMMA | General-Purpose PMMA | Impact-Modified PMMA |
|---|---|---|---|
| Light transmittance | ≥ 93% | ≥ 92% | 88–91% |
| Surface hardness | Rockwell M100 | Rockwell M95 | Rockwell M85 |
| Tensile strength | 8,500–9,000 PSI | 8,000 PSI | 6,500–7,500 PSI |
| Max temperature | 80 °C | 80 °C | 75 °C |
| Typical applications | Lenses, optics, light guides | Covers, housings, prototypes | Safety glazing, panels |
| Relative cost | High | Standard | Medium |
Optical-grade PMMA is cast to minimise internal stress and surface haze, ideal for lenses and inspection windows. General-purpose extruded PMMA is cost-efficient for functional prototypes. Impact-modified grades sacrifice some transparency to gain toughness for safety panels and vibration-exposed parts. Not sure which fits your application? See our plastic materials selection guide or contact our engineering team for a free review before quoting.
Finish Options
The final appearance of a machined acrylic part depends as much on post-processing as on cutting strategy. See the full range of surface finishes for CNC machining — multiple treatments can be combined to achieve the desired result.
Mechanical Polishing
Progressive-grit sanding (400 → 2000 grit) followed by buffing compound brings machined surfaces to near-optical clarity. Best for flat and gently curved faces where dimensional tolerance must be maintained.
Surface roughness: Ra 0.4–0.8 μm
Flame Polishing
A controlled flame passes quickly across the acrylic surface, causing the outermost molecular layer to flow and resolidify as a mirror-smooth skin. Achieves the highest optical clarity of any method — ideal for edges, channels, and contoured profiles.
Surface roughness: Ra < 0.1 μm
Diamond Fly-Cut Finishing
A single-crystal diamond tool traces the surface at high speed, leaving a sub-micron Ra finish without thermal input. Reserved for optical-grade PMMA windows and precision lenses with tight parallelism or flatness specifications.
Surface roughness: Ra < 0.05 μm
Acrylic Parts We Have Machined
Our precision acrylic components serve a wide range of industries. From medical optics to consumer electronics, precision acrylic machining spans demanding industries with uncompromising quality requirements.
Medical devices
PMMA diagnostic instrument housings with a 90% light-transmittance requirement and ±0.03 mm slot tolerances.
Electronics
Acrylic display covers prototypes, housings, and protective components for devices. cosmetic-grade front face — machined in a single 5-axis setup.
Automotive
Interior trim prototypes and inspection windows for automotive prototyping — including colour-matching fixtures and under-hood transparent covers.
Optical Components
PMMA lenses, edge-lit LED light guide panels, and optical windows with exceptional clarity.
Ready to Machine Your Acrylic Parts?
Upload your CAD files and get an instant quote. Our team is ready to help bring your acrylic parts to life with precision and quality.
ISO 9001:2015 Certified
Free Engineering Review
NDA Available
Common Questions
For transparent and functional parts, CNC machining offers much better surface quality, strength, and dimensional accuracy. FDM and SLA printing produce visible layer lines and internal stresses that compromise clarity. For small, complex internal geometries, hybrid approaches (print + machine) are sometimes optimal.
Yes. For parts with complex internal structures or undercuts, our Vacuum Casting process can produce acrylic-like parts using polyurethane resins with similar optical and mechanical properties. Quantities of 10–50 pieces often achieve lower per-unit cost via casting than CNC machining.
Yes. We stock clear, frosted, black, white, and grey PMMA as standard. Coloured cast acrylic in custom tints can be sourced on request, typically adding 2–3 business days to the lead time. All grades are available in 3 mm to 50 mm thickness.
Standard CNC machining achieves ±0.05 mm on general dimensions. With diamond fly-cut finishing on optical-grade PMMA, we achieve flatness of 0.03 mm per 100 mm and Ra < 0.05 μm. All parts are inspected per our quality control process.
Yes. We sign mutual NDAs before file transfer for any customer who requests confidentiality. Contact us before uploading files and we will arrange the agreement, typically within one business day.