PMMA (Acrylic) CNC Machining
CNC machining of PMMA acrylic: collected property envelope with service conditions, optical and cosmetic selection points, and quotation inputs.
Last updated: 2026-10-29
PMMA — acrylic, the Plexiglas family — is the optical plastic: water-clear, weather-stable, and polishable to a glass-like finish at a fraction of glass’s weight. Light guides, lenses, diffusers, signage and cosmetic panels are its natural territory, and it machines and flame-polishes cleanly into precisely those parts.
It is a hard-and-brittle plastic: elongation at break is small, notches propagate cracks, and impact is its weak suit compared with polycarbonate. Temperature service is also modest. Where a part must survive blows or run hot, the selection conversation moves — often to polycarbonate, trading some optical purity for toughness.
Specifications
| Property | Value | Condition |
|---|---|---|
| Tensile strength | 50–77 MPa | general-purpose grades |
| Flexural strength | 90–130 MPa | general-purpose grades |
| Elongation | 2–3% | at break — hard, brittle behavior |
| Continuous use temperature | 65–95 °C | maximum continuous use, working-condition dependent |
| Density | 1.17–1.20 | generic cast/acrylic PMMA |
| Hardness | Not established in the collected evidence — confirm at quotation. | |
Values above are rendered from the collected model-evidence layer, each carrying the heat-treatment condition it was reported under; fields without collected evidence are stated as not established rather than estimated. Requirements outside the table are confirmed for the specific geometry and batch at quotation.
Applications & Selection Points
Light guides, lenses and diffusers
The optical core: light-pipes, lens elements, display windows and edge-lit panels. Clarity and weatherability are why outdoor signage and automotive lamp components have trusted the material for decades. Machined edges and surfaces respond well to polishing — plan the finishing step into the quote.
Cosmetic and architectural panels
Machined fascias, instrument windows, display stands and protective screens. The material dyes and tints well, and its surface hardness — modest as plastics go — still outperforms polycarbonate for scratch resistance in handling service.
Temperature and load boundaries
Continuous hot service and structural loads are out: the usable temperature band is moderate, and stress concentrations crack it. Near heat sources or under repeated impact, polycarbonate is the tougher neighbor — at the cost of lower scratch and optical purity.
Machining and finishing planning
Brittle means the process plan matters: sharp tooling, light clamping and stress-relieving practice avoid chatter cracks; edges polish or flame-treat to clarity. Say which faces are optical — they deserve a finishing line item, and quoting them as raw-machined disappoints.
Frequently Asked Questions
Acrylic or polycarbonate for my transparent part?
Optics and scratch resistance: acrylic. Impact and temperature: polycarbonate. Acrylic stays clearer and polishable, polycarbonate survives blows and heat but scratches and needs hard coating for cosmetic life. Outdoor weathering favors acrylic. Decide which failure would actually hurt — a cracked lens or a scratched one.
Can machined acrylic parts be made optically clear?
Machined surfaces come out translucent; clarity comes from finishing — diamond turning, polishing or flame treatment on the faces that matter. It works well, but it is a process step with its own tolerance and cost. Call out optical faces explicitly so the quote includes them.
What does a quote need for machined acrylic?
The model with tolerances, sheet thickness and grade (cast vs extruded behaves differently in machining), which faces are optical or cosmetic, quantity, and any edge-finish specification (polished, flame-treated, machined-as-is).
Ordering & Documentation
Documents
Send the model with tolerances and mark optical and cosmetic faces — clarity expectations must be written, not implied. Name cast or extruded stock if the difference matters to the part.
Quotation
Priced from the model, stock form, edge and face finishing requirements, and quantity. Polishing is a genuine line item on optical work; expect it quoted separately from machining.
Sample & Supply
First articles approve optical clarity and edge finish under real light — screen inspection misses what a customer sees in use. Repeat batches run to forecast; pack with protection on finished faces.
Storage & Shipping
The material scratches: ship with masked or interleaved faces, never loose bulk. Store flat, away from heat — the sheet memory warps panels left leaning in warm spaces.