Acrylic is an extremely versatile material which is used in a wide range of environments. Acrylic sheeting is available in a huge range of variations, including; clear, coloured, mirrored, frosted and even with a brushed aluminium effect.
Extruded acrylic and cast acrylic are the two main types of sheet acrylic you will come across. Although they may initially look similar, the two have quite different properties and one is also much more expensive than the other.
It is important to be aware of the differences between the two so you can pick the type most suitable for your needs.
Extruded and cast acrylic sheets differ mainly in their thermal and chemical properties which are caused by the manufacturing process. There are also several other differences as outlined below which you may wish to consider when choosing acrylic sheet for your home DIY project.
Key differences you should be aware of when working with acrylic sheets:
Due to the way the sheets are made cast acrylic tend to have slight variations in the thickness of the sheet whereas extruded sheets are much more uniform, with next to no variation. This makes extruded acrylic ideal for vacuum forming or situations where more detailed precise shapes are needed.
Cast acrylic has an isotropic response to temperature meaning there is a maximum shrinkage of 2% in all directions. It may be important to note that acrylic expands and contracts at a much greater rate than glass. Extruded acrylic, on the other hand, shows differences in shrinkage depending on the thickness and direction of extrusion.
Benefits of Extruded sheets
Benefits of Cast acrylic sheets
Both types of acrylic benefit from being durable and long lasting, showing excellent resistance to natural aging. Most manufactures will guarantee against noticeable yellowing for approximately 10 years.
Often it may not be made obvious which type of acrylic you are buying, especially online. Cast acrylic can be as much as double the price of extruded acrylic so if nothing is mentioned and it seems cheap, the chances are it is extruded acrylic.
In vacuum forming or thermoforming fabrication, the material is just as important as the mold. If a lower-quality plastic sheet is used, the end product could be compromised. The color of the sheet could be uneven and inconsistent. Unpredictable melting could occur, causing irregular gauge thickness. Longer curing and drying could add operation time and cost to the fabrication process. In other words, having the best vacuum formable plastic sheet will always yield the best-finished product.
In short, vacuum forming is a stripped down, simpler adaptation of thermoforming. With vacuum forming, a heated, pliant plastic sheet is stretched on top or inside of a mold. The formable sheet then conforms to the shape of the mold with the application of a vacuum to ensure the plastic fills the mold, tightly and neatly. Once the sheet is formed, the vacuum is released, along with the now-formed plastic sheet.
Vacuum forming is ideal for prototyping and manufacturing parts with a shorter-run production output due to being an easy and economical operation. It is also an outstanding way to fabricate more shallow molds without the higher operational costs associated with thermoforming. Newer, technological advances have allowed vacuum forming with deeper molds, as long as the formable sheet is of higher quality and is mechanically stretched before application to the mold.
When selecting the material for your project, forming plastic is an ideal option. Vacuum formable plastic sheets, usually made of PVC (Polyvinyl Chloride) are designed especially for the vacuum forming or thermoforming process. They can withstand heat application without melting or breaking down. They are also highly regarded for their ease of processing and are inexpensive in comparison to other sheets. Be sure to choose a plastic or PVC sheet that meets your specific requirements, such as thickness, color, surface texture, and overall size. Look for a product that offers precise gauge control and consistent color with lot-to-lot traceability. This way, there will be no differences between manufacturing runs.
There are a variety of applications that benefit from both vacuum/thermoforming and formable plastic sheets. The production of kiosks and automated teller machines include external plastic structures that accommodate delicate, internal mechanisms securely and with branded aesthetics. Since the formable sheets are highly customizable, medical device housing and electronic equipment cases can be properly fitted for a precise fit and appropriate protection. On a smaller scale, electrical components are a perfect application because of the inherent flame retardance of the formable plastic sheet material.
If you are considering your options for a small run of manufactured molded parts or experimenting with a prototype, vacuum forming/thermoforming with vacuum formable plastic sheets is an excellent choice. While the manufacturing process itself is straightforward, the selection of an industry-proven formable sheet will provide high-performance durability without cutting into your bottom line. Be sure to choose a high-quality formable plastic sheet that will hold up to the demands of your next project; you will have a consistent, reliable end product every time.