Cast Acrylic Sheet: Thickness, Fabrication & Optical Clarity Guide

Content

1 Thickness Options for Cast Acrylic by Application
2 Fabrication Methods for Cast Acrylic Sheet
3 Optical Clarity and Light Transmission Performance
4 Edge Finishing and Polishing Methods
5 Application-Specific Selection Guide

Direct Conclusion: Cast acrylic sheet offers thicknesses from 0.8mm (film grades) to 100mm (architectural glazing), with 1.5mm-25mm most common for fabrication. Optical clarity achieves 92% total light transmission (higher than glass at 89%) with 0.5% haze for clear grades. Compatible fabrication methods: laser cutting (1-25mm), CNC routing, diamond drilling, and thermoforming at 150-180°C. Thinner sheets (1-5mm) suit display cases; thicker (15-50mm) used for aquariums and machine guards.

Cast acrylic sheet (polymethyl methacrylate, PMMA) is manufactured by cell casting between glass plates, producing material with superior optical clarity and stress resistance compared to extruded acrylic. The casting process yields consistent thickness, better chemical resistance, and excellent thermoforming properties. For complete technical data sheets and color options, visit the cast acrylic sheet product catalog.

Thickness Options for Cast Acrylic by Application

Cast acrylic sheet is available in nominal thicknesses from 0.8mm up to 100mm. Actual thickness tolerance for cast sheet is ±5% (versus ±10% for extruded), allowing precise fabrication. Standard sheet sizes: 1220 x 2440 mm, 1524 x 3048 mm, and 2032 x 3048 mm.

Thickness Range	Typical Applications	Fabrication Method	Weight (kg/m²)
0.8 - 1.5 mm	Display windows, membrane switch overlays, photo frames	Laser cut, die cutting	1.0 - 1.9 kg
2 - 5 mm	Point-of-purchase displays, picture frames, light panels	Laser/CNC, bending, gluing	2.4 - 5.9 kg
6 - 10 mm	Signage, shelving, machine guards, shower screens	CNC routing, drilling, polishing	7.1 - 11.9 kg
12 - 20 mm	Aquariums, security glazing, furniture, reception counters	Saw cutting, edge bonding, thermoforming	14.3 - 23.8 kg
25 - 50 mm	Large aquariums, bullet-resistant glazing, optical components	Water jet, multi-pass saw, annealing required	29.8 - 59.5 kg
60 - 100 mm	Deep-sea viewing windows, nuclear shielding, optical lenses	Specialized water jet, diamond tools, stress relieving	71.4 - 119 kg

Fabrication Methods for Cast Acrylic Sheet

Cast acrylic is more fabrication-friendly than extruded acrylic due to lower internal stress and wider molecular weight distribution. Below are the primary methods with specific parameters.

Cutting Methods

Laser cutting (1-25mm thickness): CO₂ laser (80-400 watts) produces flame-polished edge. Parameters: 10-30 mm/s speed, 80-100% power. Edge quality superior to mechanical cutting. Not recommended above 25mm due to taper.
CNC routing (2-50mm): Single-flute carbide cutter, 12000-18000 rpm, feed rate 1.5-3 m/min. Use compressed air cooling to prevent melting.
Table saw (3-50mm): Carbide-tipped blade with 60-80 teeth, negative rake angle. Cut at 3000-4000 rpm with blade projection 12mm above material.
Water jet (5-100mm): Garnet abrasive, 380 MPa pressure. Produces satin edge requiring polishing. Best for thick sheet over 40mm.

Drilling and Hole Making

Twist drill: Standard HSS drill ground to 90° point angle (not 118°). Back-up wood prevents exit cracking. RPM: 1000-2000 for 5mm holes, 500-700 for 20mm holes.
Forstner bit: Best for holes 10-50mm diameter. Slow speed 400-600 rpm, light feed pressure.
Laser drilling (thin sheet): For holes under 3mm diameter in sheets under 6mm thickness.

Critical fabrication rule: Anneal cast acrylic before machining if material has visible stress (birefringence under polarized light). Heat at 80°C for 2 hours per 10mm thickness, then cool 1 hour per 5mm thickness.

Thermoforming and Bending

Cast acrylic is ideal for thermoforming because the amorphous polymer structure allows even heating and stretching. Key parameters:

Oven temperature: 150-180°C (300-350°F). Do not exceed 190°C to avoid bubbling.
Heating time: 2-3 minutes per 1mm thickness (example: 3mm sheet = 6-9 minutes).
Line bending (strip heating): Use nichrome wire heater at 160°C. Heating time for 3mm: 45-60 seconds. Bend radius minimum 3x thickness.
Vacuum forming: Forming temperature 160-170°C. Draft angle required: 3-5° minimum. Shrinkage allowance: 0.5-0.7%.
Pressure forming: For high-detail parts (buttons, knobs). 2-5 bar pressure, mold temperature 80°C.

Optical Clarity and Light Transmission Performance

Cast acrylic offers the highest optical clarity among transparent plastics, exceeding glass for specific metrics:

Optical Property	Cast Acrylic (3mm)	Glass (3mm float)	Extruded Acrylic (3mm)
Total Light Transmission (visible)	92%	89-91%	91%
Haze (clear grade)	0.5%	0.2-0.5%	0.8-1.2%
Refractive Index (nd)	1.491	1.523	1.490
UV Transmission (350nm)	3% (UV blocking grade available)	85% (without coating)	5%
Yellowness Index (after 1000h QUV)	ΔYI < 2.0	ΔYI < 0.5	ΔYI 4-6

Cast acrylic outperforms extruded acrylic in optical clarity due to absence of residual stress lines (extruded sheets show parallel flow lines under polariscope). For display applications, cast acrylic provides crystal-clear edges when laser cut, whereas extruded can develop micro-cracks at cut edges.

Edge Finishing and Polishing Methods

For premium display and signage applications, edge finish quality determines perceived product value.

Flame polishing: Hydrogen-oxygen flame sweeps over cut edge at 50-100 mm/s. Produces crystal-clear edge. Only for cast acrylic (extruded crazes). Risk of edge distortion on thin sheet under 3mm.
Diamond polishing (mechanical): Progressive grits 240, 400, 600, then 1200. Final buff with cerium oxide. Produces matte satin finish, not optically clear.
Solvent polishing: Methylene chloride wipes edge. Creates smooth surface but may cause stress cracking in fabricated parts. Not recommended for load-bearing edges.
Laser cut edge: Flame-polished automatically. Best for letters and complex shapes where flame polishing is difficult.

Application-Specific Selection Guide

Retail Displays and POP: 2-5mm cast acrylic, laser cut, flame-polished edges. Water-clear grade for high perceived value. UV-stabilized if near windows.

Aquariums and Vivariums: 12-25mm cast acrylic, CNC routed edges, solvent-bonded with methylene chloride. Require stress-relieved annealing before bonding. Light transmission 92% maintains color fidelity.

Machine Guards and Safety Shields: 6-12mm impact-modified cast acrylic. Laser cut or water jet. Haze tolerance higher (2-3% acceptable). Specify abrasion-resistant coating for cleaning.

Signage and Light Boxes: 3-8mm, thermoformed for dimensional letters. Edge-lit signs require 92% transmission - cast acrylic outperforms polycarbonate which has 86-89% transmission.

Optical Lenses and Light Guides: 10-50mm, diamond-turned surfaces. Require optical-grade cast acrylic (less than 0.3% haze). Light transmission 92-93% at 3mm, 89% at 25mm thickness.

For detailed fabrication guidelines, optical test reports, and material selection for specific applications, explore the complete cast acrylic sheet range. Technical support for laser cutting parameters, thermoforming tool design, and bonding methods is available. Standard sheets (3mm, 5mm, 10mm) ship within 48 hours; custom thicknesses and sizes require 10-14 working days.