Cast Acrylic Sheet PMMA
Comprehensive technical specification for cast acrylic sheet (PMMA) used in Canadian fabrication, woodworking, and machining operations. Includes exact tolerances, standard sheet sizes, machinability traits, and common floor defects.
Material Overview & Common Uses
Cast acrylic sheet (PMMA) is a high-clarity, UV-stable thermoplastic widely used in Canadian fabrication shops for signage, point-of-purchase displays, light diffusers, aquariums, protective barriers, and architectural glazing. Unlike extruded acrylic, cast acrylic offers superior optical clarity, better chemical resistance, and more consistent thickness tolerance. It is available in a range of colours, textures, and surface finishes (gloss, matte, satin). Common thicknesses range from 1.5 mm to 25 mm, with standard sheet sizes of 1220 mm x 2440 mm (4' x 8') and 1525 mm x 3050 mm (5' x 10'). Cast acrylic is preferred for applications requiring high transparency, low haze, and excellent weatherability. It is also used in CNC routing, laser cutting, and thermoforming operations.
Core Technical Properties & Sizing
| Property | Value / Standard |
|---|---|
| Thickness Tolerance (≤6 mm) | ±0.5 mm (ASTM D4802) |
| Thickness Tolerance (6–12 mm) | ±0.8 mm (ASTM D4802) |
| Thickness Tolerance (12–25 mm) | ±1.0 mm (ASTM D4802) |
| Standard Sheet Sizes | 1220 x 2440 mm / 1525 x 3050 mm / 1830 x 2440 mm |
| Density | 1.19 g/cm³ |
| Tensile Strength | 70–80 MPa (ASTM D638) |
| Flexural Modulus | 3.1 GPa (ASTM D790) |
| Impact Strength (Izod notched) | 0.2–0.4 J/cm (ASTM D256) |
| Hardness | Rockwell M-95 (ASTM D785) |
| Light Transmission | 92% (ASTM D1003) |
| Haze | <1% (ASTM D1003) |
| Coefficient of Thermal Expansion | 7.0 x 10⁻⁵ /°C |
| Max Continuous Service Temperature | 80°C |
| Flammability | UL 94 HB (Self-extinguishing) |
| Water Absorption | 0.3% (24 hr, ASTM D570) |
| Chemical Resistance | Resists dilute acids/alkalis; attacked by ketones/esters |
| UV Stability | Excellent (UV-stabilized grades); yellowing possible in non-stabilized |
Machinability, Tooling & Feeds
| Operation | Parameter | Recommendation |
|---|---|---|
| CNC Routing | Tooling | Single-flute or O-flute compression cutter (carbide/PCD) |
| CNC Routing | Spindle Speed | 12,000–18,000 RPM |
| CNC Routing | Feed Rate | 2–5 m/min |
| CNC Routing | Cooling | Coolant mist or compressed air |
| Drilling | Spindle Speed | 3,000–6,000 RPM |
| Drilling | Feed Rate | 0.1–0.3 mm/rev |
| Drilling | Point Angle | 118° (slow helix to reduce chipping) |
| Laser Cutting | Laser Type | CO₂ (10.6 µm) |
| Laser Cutting (6 mm) | Speed / Power | 10–20 mm/s at 80–120 W |
| Thermoforming | Preheat | 80°C for 2 hours |
| Thermoforming | Forming Temperature | 150–180°C |
| Sawing | Blade Specs | Carbide-tipped, 80–100 teeth, 0° hook angle |
| Tapping | Thread Form | 60° thread form, 75% thread depth |
| Edge Finishing | Method | Scraper / 400–600 grit sandpaper / Flame polish |
Common Defects & Quality Control
| Defect | Cause | QC Limit / Action |
|---|---|---|
| Surface Scratches | Improper handling / storage | Max 2 per sheet, <0.1 mm deep, <50 mm long |
| Edge Chipping | Dull tooling / aggressive feeds | Reject if visible after finishing |
| Crazing | Chemical attack / thermal stress | Reject immediately |
| Bubbles / Voids | Improper casting / contamination | Max 3 per sheet, <0.5 mm diameter |
| Yellowing | UV exposure (non-stabilized) | Reject if discoloured |
| Warpage | Uneven cooling / improper storage | Reject if >1 mm bow across 1220 mm |
| Haze / Cloudiness | Moisture / improper processing | Reject if >1% haze |
| Delamination | Poor bonding (laminated grades) | Reject immediately |
| Stress Cracking | Solvent / mechanical stress | Reject immediately |
| Thickness Variation | Poor casting control | Must be within ±0.5 mm (≤6 mm sheet) |
Storage, Handling & Racking Guidelines
Store cast acrylic sheets vertically in a dedicated rack with padded supports (e.g., foam or rubber) to prevent scratching and warpage. Keep sheets in original packaging (polyethylene film) until use. When handling, wear clean cotton gloves to avoid fingerprints and oils. Use a two-person lift for sheets >1220 mm. Implement FIFO (first-in, first-out) inventory rotation. Inspect incoming sheets for damage and record defects. For waste management, segregate scrap acrylic for recycling (PMMA is recyclable).
| Parameter | Specification |
|---|---|
| Storage Orientation | Vertical, 5–10° from vertical to prevent bowing |
| Max Stack Height | 20 sheets per rack |
| Temperature Range | 15–25°C |
| Relative Humidity | 40–60% |
| Rack Dividers | Padded, spaced at 150 mm intervals |
| Environmental Protection | No direct sunlight, heat sources, or chemical fumes |
| Inventory Rotation | FIFO (First-In, First-Out) |
| Shipping Protection | Edge protectors and corrugated cardboard interleaving |