acrylic, lexan and plastics FAQ

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Here’s yet another of my forum posts archived here on my own site for posterity. This is a FAQ document I drew up on construction techniques for working with plastics.

Q: What is the difference between Lexan/Acrylic/Plexiglass etc.

A:
Lexan is a trademark of GE plastics.
Plexiglas is a trademark of the Atoglas division of Atofina Chemicals. (Thanks to Larry Daniel of Atofina for the correction)
Lucite is a trademark of E.I.DuPont DeNemours & Co.
Acrylite is a trademark of American Cynamid Co.
Perspex is a trademark of ICI Group.

Lexan is polycarbonate.
Plexiglas, Lucite, Acrylite, Perspex and acrylic are polyacrylate.

Polycarbonate is harder than polyacrylate, and if someone wants to go dig up the physical properties listings, there’s probably a wealth of other differences. I don’t think it matters much in a case modding context.

Lexan is much more shatter resistant than Acrylic. Acrylic is more scratch resistant than Lexan.

Acrylic is available in different grades:
Extruded material is manufactured by pushing pellets through a highly polished die. There can be slight imperfections in the surface. Extruded material is usually less expensive and more difficult to work with.

Acrylic can also be cast There are different casting methods, with the more expensive material being more uniform in thickness. Cell cast is the highest grade, and continuous cast is in the middle.

For more material properties, see MatWeb
For additional plstics information, try Plexiglas primer.

Q: What are some good plastic suppliers sites?

A:
Ridout Plastics
San Diego Plastics (hurts my eyes)
US Plastic
Modern Plastics
TAP
Delvie’s

But always check your local area for the best deals first.

Q: How do I glue acrylic pieces together?

A: IPS Weld-on #3 or #4 are suitable adhesives available from your plastics supplier. You can use other products, but these are specially formulated. Use #3 if you’re working with Lexan. Use #4 if you’re working with Acrylic. #3 may make your seams appear cloudy if applied in humid conditions. The adhesive is the consistency of water. Use a needle applicator available from your supplier to apply the adhesive. Edges to be glued should not be polished. Use corner clamps to hold the joint together under mild pressure. Apply the cement to the inside of the joint, keeping the joint horizontal. The adhesive will flow into the joint by capillary action. The bond will set in about an hour, but allow eight hours or more for the adhesive to fully cure before removing the clamps.

Q: Can I form/bend Acrylic sheet?

A: Use a heat gun to get the material warm enough to soften. Use a form to control the shape of your pieces. Lining your form with felt can help prevent the plastic sticking to the form (thanks, mashie). Acrylic is flammable, so using a torch to heat it for forming is a bad idea. Thicker material will need to be heated on both sides. Plastic supply houses also carry strip heaters for bending.

Q: How do I drill holes in Acrylic?

A: The best choice is a drill bit designed for plastics. It will have a different cut angle than a bit for metals. Plastic bits are available from your plastics supplier. You can successfully use an ordinary drill bit. Use a low speed, and use a bit of soap to lubricate the bit. Don’t advance the bit too far at once–back it out occasionally. Using a drill press is preferable to a hand drill.

Q: How do I cut Acrylic?

Leave the protective paper or plastic in place during cutting.

A: For straight cuts, in order of preference:

Have your supplier cut it. Their tools are better.
Use a router.
Use a tablesaw with a triple-cut blade (blade > $100)
Use other circular saw, with a blade with > 5 teeth per inch, 0 degrees rake.
Use a jigsaw with a finetooth blade. (plastics stores carry one, or use a metal blade)
Score and break the piece (best for 1/8″ material)
Use a rotary tool at s l o w speed
Use a hacksaw
Use kung fu

When sawing material thicker than 1/8″, use water to cool the blade during the cut. A little soap or wax on the blade can help with lubrication.

Q: Can I polish up the edges of my piece?

A: Do not polish edges that are to be glued. But other edges can be polished by successively sanding with finer grit sandpaper, or using a buffer and compound, or flame polishing.

To get a sharp edge with sandpaper, use a sanding block to keep the edge flat. If you want a rounded edge, use hand sanding. Using wet/dry sandpaper with water will give the best results.

Using a buffer can polish your edge very quickly. Either sand until smooth and then buff with blue compound, or buff first with red compound, then blue on a separate buffing wheel. Don’t allow the buffer to catch the edge of the material, it may get thrown.

Using a torch to polish the edges works well too on thicknesses above 1/8″. Be careful with this technique–acrylic is flammable. Using a micro torch gives good control. The flame polished edges can thicken slightly, so you may not want to use the technique if that affects your design.

Q: I want to look at pretty acrylic/lexan cases, where are they?

A: Right here:
wookiecrisp: http://www.neima.com/pleximod01.shtml
qwertyuiop: http://www.emon.freeserve.co.uk/ (pics only)
arby: http://mp3car.com/usersites/arby/box.html
arby again: http://mp3box.2y.net/case
Jayme: http://www.reality.net/case/
Princess Die: http://plexi.dbltree.com/ (warning: flash intro!)
ftjandra: http://www.mindspring.com/~ftjandra/plexi_cube/
delbert: http://forums.bit-tech.net/showthread.php?s=&threadid=10864
linear: http://www.bit-tech.net/article/72/

Q: My drill bits chip up the plexi/acrylic when I drill holes. Isn’t there a better way?

A: (courtesy of Cold Dog) Though pricey, I highly recommend the plastic drill bits over at US Plastic. I bought all the sizes from 1/4″ down and they leave a nice clean hole. Using a regular drill bit is not too bad if you are drilling with a 1/8″ drill bit or less but going larger and it starts to become chip city. If you must use regular drill bits, start small and work your way up one size at a time. Though I haven’t tried it, one recommendation I’ve heard of is to flatten the cutting edge on a regular drill bit and supposedly it won’t chip the plexi. Might extend the life of those old, worn out drill bits…

A: The Craftics Plas-Drill bits are quite nice. They have a 90° face angle and do quite nicely in a drill press. Pros use custom ground bits with diamond dust impregnated on their surface. The Craftics are quite adequate for DIY use.



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