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Obssessed Haunter
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I've seen this discussed a little, but no one has ever talked about bending a 4x8 sheet of thin plexi into a semi circle.
Any idea ?

If I had something the shape I wanted.... then lay the plexi on top of it.. would there be any way that a HOT summer day would slowly bend the latex if it was our in the sun ?
Or if I did this AND used a heat gun on it... I just didn't know if the heat gun would do the job on such a large piece of plexiglass.

Ultimately, I want to make a TUBE out of plexiglass. 2 sheets of plexi would give me a circle about 2 1/2' in diameter. Big enough for a body.
 

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Sorry Lynn, but plexi needs to get up to about 180-225 degrees to get a smooth bend out of it and a heat gun is too localized to do what you're looking for. you can buy plexi glass piping and tubes up to a 12-14 inch diameter in any length you could possibly want. What are you going to build, and what size pipe do you need?
 

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oops... scratch that last sentence I should learn to read the posts all the way through, you should be able to find what you are looking for from a plexi glass manufacturer, you can look them up on line. Most will sell items to the public. Good luck.
 

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A heat gun might work. Just slowly work your way around. I have used a torch held above the surface to heat smaller pieces. The trick is if you heat it too much it will shrink and then start to curl.

You may want to give the hot summer day a try, but keep in mind if the plastic is resting on grass you will create a green house that is remarkably efficient at killing grass.

For ease, I would recommend a bank of heaters so the surface is evenly heated making bending much easier. Plexi sets up remarkably quickly and I don't think you could get even bends with a single heat gun.

Edit: Another alternative you may want to look at is rotocasting with clear resin.
 

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1031 Props
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A radiant heater might do the trick. I have one that i bought from home depot for 60.00 that attaches to a propane tank. It Kicks out about 30k BTU. what you could do is either set the Plexiglass in front of it and slowly bend it that way. Or, you couldgo over it since heat rises. this would allow the heat to weaken the plexi glass and gravity would create your bends and curves.

This is what i have and it gets HOT! in fron of it and above when its cranked all the way up.
 

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Bending a large sheet

I've done this before by laying the sheet on top of a cardboard concrete tube then placing some weight on either side of the tube then using a heat gun to slowly and evenly heat the plexi where it covers the tube. The tubes can be found at Home Depot or Lowes cheap and come in diameters up to 12" and 3 or 4 ft. long. Laying the sheet on some black paper in the sun might help the process along but I think the heat gun will be needed to get it to the bending point.
 

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Hey a cheap way to pick up plexi glass is go to your local hockey arena and ask if they have old plexi glass that they are looking to get rid of.
It has to be a indoor arena too.
 

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Please I'd just like to say to all of you before you go and start heating up plexi glass with heat guns and radiant heaters - plexi gives off noxious and carcinogenic fumes when heated :eek:, please if you do this do it in a well ventilated area, and use extreme caution as plexi is also very flamable when heated also. I've had a great deal of experience with plexi glass over the years. It's a great material but just proceed with caution.:rolleyes:
 

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Obssessed Haunter
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Discussion Starter #11
Didn't think about the bank of heaters ! That may work. I figured the heat gun would not heat a large enough of an area.... then when the gun was moved to a new area... the old area would cool down !

I figured I would use some type of 'tube' for a jig or pattern... Just gotta figure out how to heat it....
Thanks for the help everybody. And I'll keep in mind to work with it in a place thats ventilated well.
Deathly, have you done a piece of plexi that large ?
 

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for an extreme way if you had access to a steel pipe the circumface that you needed you could clamp the sheet to the outside throw some hot coals wood or BBQ inside the pipe and after awhile the pipe will get hot couple hrs then you can slowly bend it around the pipe and clamp as you go.after your done remove the coals allow to cool couple hrs and slide it off. Or cut you some circles the size you need 3-4 maybe more space them out attach 2x2 between each circle and then attach sheet metal over the circles so you have a wood frame with sheet metal skin then clamp your plexi and heat away with a propane heater or use an old baseboard heater on some kinda stand.the sheet metal will help spread out the heat and help keep it all warm all over.
 

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One last thing, when heating plexi keep your heat source in constant motion as plexi "blisters" when heated too much in on spot, bubbles erupt from the surface and scar your plexi. good luck
 

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[Deathly, have you done a piece of plexi that large ?[/QUOTE]

Yes, my brother and I used it to make windshields for boats. The trick is to heat it evenly and slowly and let gravity do the rest. Over heating will cause problems and fumes so be careful. You might also check to see if you've got any plastic fabrication shops around. The one near us has a heated roller setup now for doing this very nicely. They make podiums and display cases this way. I've been able to get scraps of plexi and methylene chloride (the solvent that welds plexi together) from them, they are always interested in my projects.

You might also consider making a hexagon or octagon by making bends at even intervals with a strip heater. We made a jig out of steel angle iron and a few of electric water heater elements to do this. For round bends we used an old spot light strip loaded with heat lamps in a row. We clamped it to legs with casters so we could adjust the heat somewhat by raising or lowering or moving it over the plexi.

We always work outside or in an open garage so fumes were never an issue.
 

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Obssessed Haunter
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Discussion Starter #15
Thanks Deathly.... at least I know its possible. I think I will just try making my "jig". And apply heat to it... maybe with a salamander type heater ( or 2 or 3 of them).... Sounds like if I just don't over heat it and take my time.... I'm gonna have to wait until summer, so I can do this outside.
I don't have any kind of plastics manufacturers around....

Thanks all..... at least I feel a little confident that I can possibly do this !
 
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