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Thread: vacuum forming plastic types...

  1. #1
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    vacuum forming plastic types...

    From what I understand, styrene, A.B.S., butyrate, vinyl, and acetate are the best plastics used for vacuum forming. Are there any others? Can you use acrylic like plexi-glass?

    I was also wondering what objects are made of this type of plastics, lying around the house. I wanted to experiment a little with plastics I can find before purchasing large sheets. I have read that you can form your own sheets in the oven, but I am not sure which plastics to use.


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  2. #2
    Quote Originally Posted by chroniccodez View Post
    From what I understand, styrene, A.B.S., butyrate, vinyl, and acetate are the best plastics used for vacuum forming. Are there any others? Can you use acrylic like plexi-glass?
    Yes, you can use acrylic. About half my vacuum formed stuff is acrylic. It's not as stretchy when hot as PETG or styrene, so it's nice to have a high vacuum system. (I have one that originally used a kitchen vacuum sealer as a vacuum pump. That worked fine, with a 7-gallon surge tank. I have a "real" vacuum pump now, so I can draw a bigger tank down in a few minutes, but the Food Saver worked fine for small stuff.)

    You can also vacuum form some foams. I make stuff out of EVA "craft foam"---the colored foam they sell at craft stores---and it's easy on regular homemade gear using a kitchen oven. (One tip, though---it has a fairly low thermoforming temperature, and it doesn't ever sag.) I use 2, 3 and 4 mm craft foam to make form-fitting flexible rubbery masks. The 2 mm foam is very cheap, and makes a very flexible form-fitting mask that fits like a glove if you form it over a life cast of a face. The 3 mm is 3 times stiffer, which is good for masks with not-form-fitting parts, and the 6 mm stuff is several times stiffer than that. (Stiffness is proportional to the cube of the thickness, so doubling the thickness makes it 8 times more rigid.) I've also vacuum-formed 10 mm lightweight EVA foam from a camping mat, with no problems. (Naturally, it rounds shapes out quite a bit, to about a half-inch radius.)

    Recently I tried vacuum forming some 1/4" thick plastic which I think is Sintra or Celtec or something similar, which I got from the dumpster behind a plastics place. (Sintra's a slightly-foamed rigid PVC-and-something-else blend plastic, about half the density of solid plastic, usually used for signage.) I did manage to vacuum form it, but burned the surface in places a bit. I need to refine my technique some, but I think it will work great after a couple more tries. I made a mask out of the 1/4" stuff, and where it wasn't a little burned (a streak of tiny zit-like bubbles) it has a beautiful glossy very-finely-textured surface. It is also strong enough to stand on.

    I think the Sintra-type stuff is going to turn out to be very useful for making fairly strong objects like equipment housings and maybe paintball masks. It's dense enough that it's not fragile, but because it's not TOO dense, you can make thicker and therefore stronger things out of it, without it being ridiculously heavy. (Halving the density lets you make it twice as thick and therefore considerably more rigid for the same amount of plastic, while still having a fairly hard surface which is nice in itself, and can take paint well.)

    I'm going to have to get some 1/8" Sintra... that should be a breeze to vacuum form. (At least with a high-vac system.)

    Another plastic that people use is polycarbonates like Lexan. That's the stuff that CDs and DVD's are made of (and expensive non-disposable water bottles). It's very tough stuff. People use it to make RC car and truck bodies, among other things, because it can take a lot of abuse.

    You can buy various-sized sheets of acrylic (Plexiglas, Perspex, and Acrylite are some of the brand names) and polycarbonate (Lexan et al.) in the glazing department of a home improvement store like Lowes or Home Depot. It's not really cheap, though---if you're going to use much of it, you're better off buying bigger sheets from a plastics place.

    If you're experimenting on the cheap, try hitting the dumpsters behind sign shops, small plastics places, and maybe places that make custom windows.

    Some people also vacuum form polyethylene and polypropylene, but I've never tried those. (Polyethylene is the stuff that a lot of recyclable drink bottles are made out of, that's milky white.)

    Some people vacuum form thin rigid sheet foams, like thinly-sliced Styrofoam. (The blue fine-textured stuff, or the pink Owens Corning equivalent, not the coarse white bead foam, which will come apart after you heat it.) It's apparently somewhat tricky, but I intend to try it.

    I was also wondering what objects are made of this type of plastics, lying around the house. I wanted to experiment a little with plastics I can find before purchasing large sheets. I have read that you can form your own sheets in the oven, but I am not sure which plastics to use.
    One of my favorite plastics is suspended ceiling diffuser panels for fluorescent lights---2 x 4 sheets of textured styrene or acrylic. The clear "cracked ice" texture is just beautiful, and the "white mist" (if you can find it) is a nice fine-grained texture for translucent stuff. (Like making light diffusers.)

    If you form those textured plastics over a positive buck with the flat side out, you get a muted version of the texture coming through on the outside, so you can get surfaces that are smooth but randomly irregular, like beaten metal.

    If you want to make small, clear things, you can use 3-liter pop bottles. They're made of PETG, which is easy to vacuum form. (People use them for model airplane cockpit canopies and sometimes nose cowlings.) If you cut the ends off a 3-liter bottle and split it at one of the mold marks, you can unroll it and get a nice little rectangle of PETG about 6 inches or so by 13 inches or so. (With an unfortunate mold mark right across the middle.) Let the PETG dry for a couple of days if the bottle recently had liquid in it.

    Another source of small clear plastic---usually clear PVC, I think---is packaging. Look for the big blister packs for various consumer items, which often have a flat piece for the back. (Or the lids to boxes like greeting cards come in.) If you decide you like the stuff, though, it's worth buying in big sheets from a plastics supplier. (Thin stuff is not very expensive per square foot in 4 x 8 sheets from a plastics supply place. Once you're buying big sheets, you're mostly paying for the actual material, not the sheet, so the cost is roughly proportional to the thickness of the plastic)

    Last edited by drcrash; 04-02-2007 at 04:03 PM. Reason: tag typo


  3. #3
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    Wow! Thanks drcrash! I think you covered just about everything haha.

    I was wondering, how much vacuum power do you think I would need for acrylic forming? I will be using acylic sheets no more than 1/4" thick, but most likely I will be sticking to 1/8".

    I am a student at the moment so I am completely broke. So I will be building my own vacuum system.



  4. #4

    cheap but good high-vacuum system

    Quote Originally Posted by chroniccodez View Post
    I was wondering, how much vacuum power do you think I would need for acrylic forming? I will be using acylic sheets no more than 1/4" thick, but most likely I will be sticking to 1/8".

    I am a student at the moment so I am completely broke. So I will be building my own vacuum system.
    I like having high vacuum for 1/8" acrylic, and you'd definitely want it for 1/4".

    What are you making? Some things don't need a very strong vacuum, because they don't have any sharp concavities you need to pull the plastic into.

    How big a machine do you need?

    Have a look at my high-vacuum system for my small machines... this cost me less than $50 because I found a "vacuum pump"---a kitchen Food Saver vacuum sealer---for $3 at the Goodwill Blue Hanger store:

    http://www.hobbymolding.com/hm_forum...opic.php?t=365

    A warning---there's porn spam at the end of the thread. (The hobbymolding site has been overrun by spammers and apparently there's nobody actually moderating it.) Sorry about that.



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