Cast acrylic is made by pouring liquid MMA (methyl methacrylate) resin into glass molds and letting it cure. Extruded acrylic is made by pushing heated resin through rollers at high speed. Both types transmit up to 92% of visible light and weigh about half as much as glass. But the manufacturing method creates real differences in tolerances, machining behavior, chemical resistance, and price that affect which one you should pick for your project. For more information, see the poly(methyl methacrylate) (Wikipedia).
I've worked with both types for years at KASTLITE, and the short version is this: cast acrylic machines better, comes in more colors and thicknesses, and resists chemicals and crazing. Extruded acrylic costs less, has tighter thickness tolerances, and thermoforms more easily. The right choice depends on your application. For more information, see the cast acrylic (Wikipedia).
How Cast Acrylic Is Made
Cast acrylic starts as liquid MMA monomer. Manufacturers pour this liquid between two sheets of tempered glass separated by a flexible gasket. The assembly goes into an autoclave or water bath where heat triggers polymerization. The resin hardens into a solid sheet over several hours.
This slow curing process produces longer polymer chains with higher molecular weight. The result is a harder, denser sheet with better scratch resistance and optical clarity than extruded alternatives. Because each sheet is made individually (or in small batches using cell casting), manufacturers can produce a wide range of thicknesses, from less than 1mm up to 100mm or more. Color options are also broader since each batch can use a different pigment formula.
The tradeoff is speed. Cell casting is labor-intensive and slow compared to extrusion. That's the main reason cast acrylic costs more.
How Extruded Acrylic Is Made
Extruded acrylic uses a continuous manufacturing process. Acrylic pellets or granules are fed into a heated barrel, melted, and forced through a die. The molten material passes between polished rollers that set the final thickness. The sheet cools as it moves down a conveyor and is cut to standard sizes.
This process runs continuously and produces large volumes quickly. The polymer chains in extruded acrylic are shorter than those in cast acrylic because the resin doesn't have time for full polymerization. Shorter chains mean the material is softer, has a lower melting point, and bonds more easily with solvent cements.
Extruded sheets typically max out around 20mm thick, though most suppliers stock up to about 10mm. The continuous process limits color variety since changing pigments requires stopping and purging the entire production line.
Cast vs Extruded Acrylic: Side-by-Side Comparison
| Property | Cast Acrylic | Extruded Acrylic |
|---|---|---|
| Manufacturing method | Poured into molds, slow cure | Pushed through rollers, continuous |
| Light transmission | Up to 92% | Up to 92% |
| Thickness tolerance | Wider (varies by thickness, roughly +/- 10-15%) | Tighter (roughly +/- 5% or better) |
| Maximum thickness available | Up to 100mm+ | Typically up to 20mm |
| Molecular weight | Higher (longer polymer chains) | Lower (shorter polymer chains) |
| Hardness | Harder, more scratch-resistant | Softer |
| Chemical resistance | Better, resists solvents and crazing | Lower, more prone to crazing from solvents |
| Laser cutting performance | Clean edges, less melting, polished finish | More likely to melt and produce rough edges |
| Thermoforming | Higher forming temperature needed | Lower melting point, easier to thermoform |
| Solvent cementing | Bonds well but requires more time | Bonds faster and easier |
| Color and finish options | Wide range (small batch flexibility) | Limited (continuous process restricts changes) |
| UV resistance | Degrades only about 3% over 10 years outdoors | Similar UV stability when UV-stabilized |
| Price | About 20% more expensive | Lower cost per sheet |
When to Choose Cast Acrylic
Cast acrylic is the better choice when your project demands precision machining, optical clarity, or long-term durability. Here are the most common applications where cast wins:
Laser cutting and engraving. Cast acrylic produces clean, flame-polished edges when laser cut. The higher molecular weight means the material vaporizes cleanly instead of melting and re-fusing. If you run a sign shop, display business, or maker space, cast is the go-to for laser work.
Signage and point-of-purchase displays. The wider color range and superior optical clarity make cast acrylic the standard for retail signage, museum displays, and trade show materials. KASTLITE stocks clear acrylic and colored acrylic sheets for these applications.
Thick sheet applications. Need acrylic thicker than 20mm? Cast is your only option. Aquariums, architectural glazing, and structural panels all require cast acrylic in heavy gauges.
Chemical exposure environments. Cast acrylic resists crazing from cleaning agents, solvents, and industrial chemicals better than extruded. For laboratory shields, industrial machine guards, or retail displays near fragrance products, cast is the safer bet.
Outdoor installations. High-quality cast acrylic (like Perspex or ACRYLITE) degrades only about 3% over 10 years of outdoor UV exposure. That makes it a strong fit for outdoor signs, skylights, and architectural features where the sheet will be exposed to weather for years.
When to Choose Extruded Acrylic
Extruded acrylic makes sense when budget, thermoforming, or tight thickness control matter more than machining quality. Common use cases include:
Economy glazing and protective barriers. For sneeze guards, window glazing, picture framing, and other applications where you need clear, flat sheets at a lower price point, extruded acrylic does the job. Browse KASTLITE's acrylic sheet collection for standard sizes.
Thermoforming and vacuum forming. Extruded acrylic has a lower softening temperature, so it bends and forms more easily under heat. If you're making formed trays, curved displays, or molded covers, extruded sheets will cooperate with your equipment better than cast.
Solvent bonding projects. The shorter polymer chains in extruded acrylic react faster with solvent cements like Weld-On 4 or Scigrip 16. Joints form quicker and often produce strong bonds with less effort. If your project involves a lot of cementing, extruded saves time.
Large-volume orders on a budget. When you need hundreds or thousands of identical sheets and laser cutting quality isn't a priority, extruded acrylic's lower price adds up. At roughly 20% less per sheet than cast, the savings on a bulk order can be significant.
Simple fabrication. Scoring, snapping, and basic sawing all work well with extruded acrylic. For DIY projects, school supplies, or basic construction applications, extruded is usually good enough.
Thickness Tolerance Differences
This is one of the most misunderstood differences between the two types. Thickness tolerance refers to how much the actual sheet thickness can vary from the stated (nominal) size.
Cast acrylic has wider tolerances. Because each sheet is made in a mold with flexible gaskets, there's natural variation. A nominal 6.4mm (1/4") cast sheet might actually measure anywhere from 5.1mm to 7.4mm, depending on the manufacturer. That's roughly a +/- 10-15% range. The ISO 7823-1 standard defines cast tolerances using the formula: +/- (0.4 + 0.1 x nominal thickness in mm).
Extruded acrylic has tighter tolerances. The roller process produces sheets with more consistent thickness. A nominal 6.4mm extruded sheet typically stays within 5.7mm to 7.1mm, or about +/- 5%. Some manufacturers achieve even tighter control, especially on thinner gauges.
Why does this matter? If you're building a project where multiple sheets need to fit flush, like a multi-panel display or a fixture with stacked layers, extruded acrylic's consistency reduces shimming and alignment headaches. If you're machining a single thick sheet for a custom part, the tolerance difference is less of a concern.
When ordering plastic sheets for precision work, always ask your supplier for actual measured thickness, not just the nominal size. At KASTLITE, we measure and document sheet thickness so you know exactly what you're getting.
Cost Comparison
Cast acrylic typically costs about 20% more than extruded acrylic in comparable sizes. The price gap comes from the manufacturing process: cell casting is slower, more labor-intensive, and produces smaller batch sizes than continuous extrusion.
Here's how to think about cost for your project:
- Small project, few sheets: The per-sheet price difference might be only a few dollars. Pick the type that matches your fabrication needs, not the cheaper one.
- Mid-size project (10-50 sheets): The 20% gap starts to add up. If you're doing simple cuts and don't need laser-quality edges, extruded saves real money.
- Large orders (100+ sheets): The savings from extruded acrylic can be substantial. But factor in waste: if extruded acrylic melts or chips during machining, the scrap cost may erase the per-sheet savings.
Also consider the hidden cost of rework. Cast acrylic machines more predictably, so you're less likely to ruin sheets during fabrication. One ruined cast sheet is cheaper than three ruined extruded sheets that you thought would work.
For current pricing on cut-to-size acrylic sheets, check our 1/8" cut-to-size clear acrylic and 1/4" cut-to-size clear acrylic product pages.
Frequently Asked Questions
Can you tell cast and extruded acrylic apart by looking at them?
Not easily. Both types are clear and glossy in their standard form. Cast acrylic sometimes has a very slight edge in optical clarity, but the difference is hard to spot with the naked eye. The real differences show up during fabrication, not visual inspection.
Which type is better for laser cutting?
Cast acrylic, hands down. It vaporizes cleanly under a laser beam and leaves flame-polished edges. Extruded acrylic tends to melt and re-fuse, creating rough or gummy edges that need extra finishing. If you own a Glowforge, Epilog, or similar CO2 laser, buy cast.
Is one type stronger than the other?
Cast acrylic is harder and more scratch-resistant due to its higher molecular weight. But "stronger" depends on context. Both types have similar impact resistance. For applications where surface hardness matters (display cases, machine guards), cast wins. For impact resistance, they're comparable.
Can I use extruded acrylic outdoors?
Yes, as long as it's UV-stabilized. Most commercial-grade extruded acrylic includes UV stabilizers that prevent yellowing. However, cast acrylic generally has better long-term outdoor performance. Brands like ACRYLITE and Perspex guarantee minimal degradation (about 3% over 10 years) for their cast sheets.
Does extruded acrylic yellow faster than cast?
Not necessarily. Yellowing depends more on the UV stabilizer package than the manufacturing method. Both types can last decades outdoors if properly formulated. That said, budget extruded sheets without UV stabilizers will yellow faster than premium cast sheets with full UV packages.
Which type is better for bending with a strip heater?
Extruded acrylic. Its lower softening temperature means it bends at lower heat settings and is less likely to bubble or crack during forming. If your project involves a lot of heat bending, extruded is easier to work with.
What is PMMA, and is it the same as acrylic?
PMMA stands for polymethyl methacrylate. It's the chemical name for acrylic plastic. Plexiglass, Perspex, Lucite, and ACRYLITE are all brand names for PMMA sheets. Both cast and extruded acrylic are PMMA. The difference is in how the PMMA is formed into sheets, not in the base chemistry.
Shop Acrylic Sheets at KASTLITE
KASTLITE is a US manufacturer based in Clearwater, FL. We stock both cast and extruded acrylic sheets in standard sizes and offer cut-to-size services for custom projects. Whether you need clear acrylic sheets, colored acrylic, or polycarbonate alternatives, we ship direct from our warehouse.
Want to compare acrylic to other materials like polycarbonate, PETG, or PVC? See our ASTM material data reference for side-by-side specs.
Once you pick cast or extruded, you still need to choose the right thickness. See our thickness guide for application-specific recommendations.
For projects that need more impact resistance than acrylic, PETG is worth considering. See our PETG guide.
Not sure which type fits your project? Contact our team and we'll help you pick the right material. You can also explore our acrylic shapes for pre-cut circles, squares, triangles, and more.
For more material guides, read our beginner's guide to ABS plastic sheets and browse the full plastic sheets collection.