Acrylic signage sits at the premium end of the sign market: lobby logos, illuminated letters, retail displays, directional systems and awards. For buyers, the material looks deceptively uniform - a clear or colored glossy sheet - yet the difference between cast and extruded acrylic, and between a 3 mm and a 10 mm panel, decides whether a sign machines cleanly, survives outdoors for a decade, or cracks during installation. This guide explains how cast and extruded acrylic differ, how to choose a thickness for each application, and which mounting options to specify, so your next acrylic sign order arrives fit for purpose the first time.
Cast vs Extruded: Two Different Manufacturing Routes
Both materials are PMMA (polymethyl methacrylate), but they are made differently, and the process drives the properties.
Cast acrylic is produced by pouring liquid methyl methacrylate monomer between glass plates and curing it slowly in an oven - a batch process that yields a high-molecular-weight sheet with very low internal stress. It machines, engraves and laser-cuts beautifully, resists solvents, and weathers outdoors for ten years or more without yellowing. Thicknesses run from about 1.5 mm to 50 mm and beyond.
Extruded acrylic is made by forcing molten PMMA pellets through a die on a continuous line - fast, consistent and cheaper, typically 20 to 40 percent below cast pricing. Thickness tolerance is tighter (around plus or minus 5 percent), but the sheet carries more internal stress, scratches more easily, can melt or craze under laser cutting, and may yellow within three to five years outdoors unless UV-stabilized. Standard extruded gauges run roughly 0.8 to 12 mm.
Property Comparison: Cast vs Extruded
| Property | Cast Acrylic | Extruded Acrylic |
|---|---|---|
| Light transmission (clear) | Up to 92 percent | About 88-90 percent |
| Thickness range | 1.5-50+ mm | 0.8-12 mm |
| Thickness tolerance | Wider (about plus/minus 10 percent) | Tight (about plus/minus 5 percent) |
| Surface hardness / scratch resistance | Higher | Lower |
| Internal stress | Very low - clean machining | Higher - can craze or melt at edges |
| Outdoor UV stability | Excellent, 10+ years | Moderate, 3-5 years unless stabilized |
| Thermoforming | Excellent, predictable | Good; directional grain can show |
| Relative cost | Baseline (higher) | 20-40 percent lower |
Rule of thumb: specify cast for anything with visible laser-cut edges, engraved logos, solvent-bonded joints, thickness over 6 mm, or long outdoor exposure. Extruded is the sensible economy choice for thin indoor panels, protective covers and high-volume budget signage.
Choosing the Right Thickness
Thickness governs rigidity, weight, mounting method and price. Common practice in the sign industry:
- 2-3 mm - indoor displays, point-of-sale panels, printed inserts and photo frames. Too flexible for freestanding outdoor signs.
- 3-5 mm - the standard range for wall-mounted office signs, door plates and directory panels fixed with standoffs or adhesive.
- 5-8 mm - reception logos and dimensional lettering where a chunky edge reads as quality; also suitable for smaller illuminated signs.
- 8-10 mm - premium freestanding panels, countertop displays and LED edge-lit signs, where light travels through the polished edge.
- 10 mm and above - architectural features, thick trophy blocks and heavy-duty outdoor panels; cast acrylic only at these gauges.
When in doubt, go one gauge thicker on any sign larger than 600 mm in either dimension - thin large panels bow and reflect light unevenly. Weight also doubles with thickness, which affects both freight cost and the strength of the fixing hardware required.
Printing and Decoration Options
Acrylic accepts several decoration routes, and the right one depends on the look you want and the wear environment:
- Second-surface (reverse) printing prints mirrored artwork on the back of clear acrylic so it is viewed through the sheet. The glossy front protects the ink completely - the professional standard for panel signs and overlays.
- UV direct printing on the face gives vivid, scratch-resistant color for retail and exhibition graphics.
- Screen printing delivers exact spot colors and thick, durable ink for high-volume runs of simple designs.
- Applied vinyl graphics suit short runs, multi-color logos and easy updates.
- Laser engraving and CNC routing create frosted etched detail, dimensional letters and custom shapes; cast acrylic produces the cleanest engraved edges.
Back-painted or vinyl-backed colored panels are another common route to solid brand colors without printing at all.
Edge finishing deserves a line in the specification too. Saw-cut edges are matte and industrial; diamond-polished edges are glass-clear and suit visible edges on premium panels; flame polishing is a fast middle option for cast material. For any sign where the edge is visible to the customer, state the required finish explicitly - it changes both appearance and price.
Mounting and Installation Options
The mounting method should be decided at order stage, because it determines drilling and edge finishing:
- Standoff fixings - metal barrels that hold the panel 15-25 mm off the wall; the classic corporate look. Requires drilled holes, so send a fixing template with the order.
- Adhesive pads or VHB tape - invisible fixing for lighter panels on smooth walls; no drilling, but surface preparation is critical.
- Clear adhesive or screw caps - economical for door signs and notices.
- Channel and frame systems - the panel slides into an aluminium frame; good for directories with changeable inserts.
- LED edge-lighting - engraved clear acrylic lit from the edge for illuminated wayfinding; specify polished edges and cast material.
- Hanging systems - cable or chain suspension for ceilings and shopfronts.
Common Specification Mistakes to Avoid
Four errors account for most acrylic sign problems buyers report. First, ordering "acrylic" without stating cast or extruded - the quotes you compare may not be the same material at all. Second, specifying extruded acrylic for laser-cut logos, then receiving matte, stressed edges that need polishing. Third, using thin extruded sheet outdoors, where UV exposure embrittles it within a few years. Fourth, forgetting tolerances: cast sheet thickness can vary by around plus or minus 10 percent, which matters for slotted frames and assemblies - if a precise gauge is critical, say so on the order. Write the material type, thickness, finish, decoration route and mounting method into every RFQ and these problems disappear.
Indoor vs Outdoor: Where Each Grade Belongs
The indoor-outdoor question simplifies material selection considerably. Indoors - retail displays, exhibition panels, office directories, trophies - extruded acrylic performs perfectly well, because UV exposure and weather are absent; its lower cost and tighter gauge tolerance are pure advantages. Many buyers standardize on extruded for all indoor point-of-sale work and reserve cast for signature pieces.
Outdoors, the balance tips firmly to cast. Sunlight is the enemy: unstabilized extruded sheet yellows and embrittles within three to five years, while cast acrylic holds clarity for a decade or more. Temperature cycling matters too - cast's lower internal stress means fewer stress cracks around drilled fixing holes through winter freeze-thaw cycles. For illuminated signs, choose cast regardless of location: LED edge-lighting exposes every internal stress line in extruded material, while cast lights evenly along the engraved design.
How Sainthouse Can Help
Sainthouse Technology has produced custom acrylic signs in Qingdao, China since 1998. We fabricate and print cast and extruded acrylic from 2 mm upward, offering UV direct printing, second-surface screen printing, laser cutting, engraving, edge polishing and drilled mounting to your template. Minimum orders start from 500 pieces, with a finished physical sample approved before production begins. Send your dimensions, artwork and fixing method, and we will recommend the material and gauge that fits the job.
References
- Walglas - Cast Acrylic vs Extruded Acrylic: Which One Fits Your Project: https://www.walglasplastic.com/?p=1339/
- Jumei Acrylic - Cast vs Extruded Acrylic Sheets: Complete Comparison Guide: https://jumei-acrylic.com/cast-vs-extruded-acrylic-sheets-key-differences-explained/
- OLFA Plastic - Cast vs Extruded Acrylic: B2B Buyer's Guide: https://olfaplastic.com/cast-vs-extruded-acrylic-sheet-b2b-buyers-guide/
- Wetop Acrylic - Cast vs Extruded Acrylic: Cost Gap and Tolerances: https://wetopacrylic.com/guide/cast-vs-extruded-acrylic