Acrylic sheet becomes soft and pliable when heated-behaving almost like a sheet of flexible rubber. It may then be formed into almost any shape. As the sheet cools, it hardens and retains the formed shape, provided it has been held in place during the cooling process.
The only functional difference between Cast and the Extruded acrylic sheet is the temperature ranges in which they are pliable. Do not exceed them. Excessively high temperatures may cause the sheets to blister and burn. The extruded acrylic sheet will better define tight radii or deep draws.
Cast acrylic sheet should be heated to between 340° and 380°F (171° and 193°C).
Extruded sheet should be heated to between 290°F and 320°F (145°C and 160°C).
Line bending or thermoforming Abrasion Resistant acrylic sheet is not recommended. Cold forming is possible. To calculate the minimum bend radius of curvature, multiply the thickness of the sheet to be used by 330. Tighter radii may result in crazing or cracking of the coating.
Never heat acrylic sheet in a kitchen oven. Acrylic sheets produce highly flammable fumes when decomposed overheating. These gases are potentially explosive if allowed to collect in an unventilated area.
Most kitchen ovens do not have accurate temperature control. Temperatures can be off as much as 75°F (42°C), possibly allowing the acrylic to overheat.
And because air is not forcibly circulated in a standard kitchen oven, the fumes will accumulate. When they come into contact with the heat source, there will likely be an explosion. Repeat: DO NOT heat acrylic in a kitchen oven.
Forming with a strip heater
A strip heater is undoubtedly the most useful acrylic-forming device in the home craftsman's arsenal. Used properly, it is perfectly safe. A correctly assembled strip heater will not exceed safe heat. Unfortunately, a strip heater can only be used to form straight-line bends; but that is usually all that's necessary for most home projects. It will allow you to make those bends with minimal trouble and electricity.
A strip heater heats only the area to be formed. There's no need to heat the entire sheet if you only intend to make a straight-line bend. It heats quickly. And with little care, you'll get excellent results because the rest of the piece stays cool.
Heating and forming an acrylic sheet with a strip heater is not difficult. When properly heated, the acrylic may be easily bent into smooth, clean corners. With patience and a little practice, you should soon be able to achieve excellent results.
First, remove the masking paper from the line of the bend. The rest of the masking paper should be left in place to protect the unheated area. Then lay the sheet on the heater with the bend line directly above the exposed heating element so the bend will be made away from the heated side. The length of heating time will vary according to the thickness of the sheet. An acrylic sheet thicker than 3/16" (4.5 mm) should be heated on both sides for a proper bend. Heat the sheet until it begins to sag at the bend line. Don't bend the sheet before it is fully heated or partially cooled. This will result in irregular and creased corners and high internal stress.
Forming jigs and clamps should be used for best results. They can be made of wood and used over and over. Make preformed jigs for certain angles or even special shapes for individual projects. Variable angle jigs can be made with two pieces of wood hinged together and help at the desired angle with a variable brace, as shown. Felt, flannel, or flocked rubber should line any surface that may come into contact with the heated acrylic. Wear heavy cotton gloves when handling heated acrylic sheet. They'll protect your hands as well as the sheet.
Note: Acrylic sheet may be formed into almost any shape. However, specialized heating and forming equipment are usually required for all but the simplest projects.
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Title: Forming Cast & Extruded Acrylic Sheet Description: Instructions on heat forming acrylic sheet Published: 4/9/2009 Last Edited: 1/4/2023
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Cast acrylic is known for its optical clarity and superior surface finish, making it ideal for applications requiring high transparency or intricate designs. On the other hand, extruded acrylic offers better impact resistance and is more suitable for applications that require durability and strength.
One of the easiest ways to distinguish between the two is by checking the thickness of the sheet. Extruded acrylic sheets have a more consistent thickness, whereas cast acrylic sheets may show slight variations. The surface finish and optical properties are also better in cast acrylic.
Available in a broad range of standard and custom colors for a variety of applications, cast acrylic is more pliable than extruded, less likely to bend, chip, or melt during milling. Because extruded material is limited in thickness, cast acrylic is a better option for larger structures, installations, etc.
Extruded Acrylic Sheet. Acrylic is used in many industries, including signage and marine. In addition, unlike transportation, manufacturing, construction, pharmaceuticals, and food production, trade safety concerns are of glass and offer a wealth of benefits.
Initial costs of extrusions are attractive as well. Die engineering fees for new custom shapes are much less than when compared to castings. Extruded aluminum shapes are also produced with an excellent surface finish and are typically stronger in comparison.
Acrylic is a remarkably versatile material, because it is as transparent as the finest optical glass but it is also ten times as strong and only half the weight.
Cost: Extruded is marginally cheaper and therefore any requirement for a large quantity of sheets/panels, where the benefits of cast acrylic are not important, is likely to be more cost effective produced in Extruded acrylic.
This clarity means it easily replaces glass for almost any application, and extruded acrylic is far more impact resistant than glass. It also resists electrical current and UV radiation well.
You can bend both cast acrylic sheet and extruded acrylic (the budget version). With a little experience and careful preparation, you'll achieve great results! Not just professionals but also handy DIYers can get started with bending acrylic using a paint burner, a heat spiral or a convection oven.
All of the acrylic sheet Emco Plastics sells is manufactured with plenty of Ultra-violet stabilizer (UV) protection. This means that with proper maintenance of the Plexiglas® acrylic sheet, it should last 10 years or more before it ever yellows.
Thin acrylic sheets (3/16” or less) are very easy to cut by hand using a scoring knife or dull utility blade. Thicker plexiglass can also be cut by hand, but it's much easier and more efficient if you use a power tool to achieve clean, straight cuts.
Acrylic and glass also share a lot of similar qualities in the sense that they're both transparent and they both let in a lot of natural lighting. The reason acrylic costs more is because it's a lot stronger and more weather-, scratch-, and impact-resistant than glass.
While acrylic is robust, it still needs support when used in large sheets so opt for a thicker sheet when in doubt if the dimensions are on the larger side. As an example, if the sheet is up to 1.5 sq.metres, 3mm should suffice, while anything between 1.5 and 2 sq.metres should have a minimum thickness of 4mm.
Cast and extruded acrylic glass is among the thermoplastics with the highest surface hardness, as well as offering excellent scratch resistance. This is confirmed by the pencil hardness test, among others.
Furthermore, extrusion dies are relatively cheaper than die-cast moulds and are easier to make. Extrusion is an adaptable and cheaper process that can be adjusted at short notice. This makes extrusion ideal for shorter production runs.
Acrylic is available in a choice of two material types - Cast or Extruded. Cast acrylic is regarded as a better-quality material and is manufactured in smaller batches.Extruded has historically been less expensive, and manufactured in longer production cycles.
Cast engraves frosted, extruded engraves clear. Extruded smells more and worse when laser cut and engraved. Extruded often comes with a plastic backing. Cast comes with a brown paper backing.
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