Types of Plexi
Plexiglass comes in many different names, colors, and thicknesses. The types are very important as some are more flexible, scratch resistant or heat retardant. Most Plexi comes with a protective sheet covering both sides to protect it while working it.
Here are some types of plexiglass:
- Polycarbonate from hardware stores is fairly rigid, scratches and cracks easily. Has a pliability at 240°F (115.5°C), isn’t as resistant compared to UV special types. It can be found in clear, tinted, frosted, colors and UV reactive.
- Lexan is a brand name and it is more flexible, UV resistant. It is not as prone to cracking, scratching, and pliability temperature of 280°F (137.7°C). Lexan can be found in clear, tinted, frosted, colors and UV reactive.
- Acrylic is another type of plexiglass with most of the same characteristics, except it’s pliability temperature of 500°F (260°C) and doesn’t come in UV reactive.
- Copolyester is very flexible, isn’t UV resistant and has more impact strength than acrylic. It is pliable at about temperature of 250°F (121°C), and is only found in clear.
- Clear Polyvinyl Chloride (PVC) is very rigid, scratches and cracks resistant. Has a pliability at temperatures of 245° F (118°C), is good High heat as well as self-extinguishing, is not UV stabilized and comes in colors as well as clear.
All the types listed above can be cut, drilled, engraved, bent and finished with great results. Thicknesses are 1/16"(1.5mm) and up. The thickness change in size in about 1/16" increments and usually comes with a removable protective film on both sides.
Most common modding thicknesses with Protective film
Depending on the place of purchase, most of these can be in sizes from 8" x 12" (203mm x 304mm) up to full sheets which are usually 4’ x 8’(1.22m x 2.44m). With all the different types of plexi listed make sure you make the right choices on glues, cleaners and usage.
Prep work for Plexi
Once an idea is in mind, an order of process is needed. I will show you two mods as examples of different processes in layout, cutting, drilling, engraving and finishing. A clean work area is a key to any good mod and it is very important when working with plastics. It can be easily be marred compared to other parts of the PC. Your work area should be a clean surface with a clean cloth to wipe off shavings from work being done. Besides safety glasses, gloves are needed as the plastic bits coming from power tools are hot and the edges can be as sharp as glass.
Layout
When working with plastics it is a good idea to have plastic or wooden rules and squares. They are less likely to scratch the plexi by accident. Marking requires a felt tip indelible marker on the plastic protective sheet or pencil on paper protective coverings.
Layout tools
Once all the tools and measurements are at hand transfer them to the plexi glass, giving a little extra for finishing. Mark the front and double-check the layout. Like the old saying goes "measure twice-cut once".
Layout marks for a window
Layout marks for a bracket
Another important part of layout work is the order of work. This order can help with success or break the sheet. In most cases the correct order is drilling, cutting, engraving, finishing if desired and finally mounting. The reason for drilling first, especially near an edge, is so that the more material you have the safer it is and less likely to crack. Cutting is the next step. That is so that we know the piece fits with good alignment before the last steps can be done.
Drilling
A variable speed drill seems to work best and what ever size of hole you want to drill always have sharp bits. A dull bit can melt the plexi or cause a chip, crack or splinter. There are different types of bits available that work well in plastics. These include standard high-speed, step, chamber and hole saw bits.
High-speed bits – come in many sizes, and in sets. Good for small and pilot holes.
Step bit(top) – Also under the name Unibit with several sizes in steps of 1/16" on one bit.
Chamber bit(bottom) – An angled bit made for cutting for flathead screws like fan screws.
Hole saw bits – An arbor (shaft with a center bit) and a round saw to cut large holes. The arbor can used with several saws for different holes. A must do is using scrap wood to support the piece being drilled. This will help keep the plastic from chipping and protect the bits from damage. For any size hole drill a small pilot hole first so that larger bits will not move off center while drilling.
Pilot holes
Finished holes
When drilling make sure the drill is angled to the correct angle you want for the finished hole. Being a little off can make it hard or next to impossible to get things to align during assembly. Use very little pressure as too much can cause a chip or crack. With larger holes using masking tape on both sides in the area being drilled, this will help against cracking. Sometimes running a holesaw in reverse on the plexi is best, less chance of cracking and you can run it really fast.
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