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PostPosted: May 11, 2016, 1:05 pm 
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Any one know how to heat bend plastic and get a large radius out of it? like a 2" or 3" radius

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PostPosted: May 11, 2016, 2:40 pm 
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type of plastic? Matters for plastic transition temperature
thickness? you dont want to overstress the outside of the bend or it will crack even when heated
color? important for infrared heating. Also some of the pigments cause different processing characteristics
length of bend and overall size of piece? really a question about tooling and heating apparatus

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PostPosted: May 11, 2016, 2:54 pm 
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i can get any type if plastic but abs or acrylic. again i can get any thickness but maybe .125. it needs to be somewhat rigid for a mold.

the bend needs to be about 18- 24" lg

making something similar to this....
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PostPosted: May 11, 2016, 3:18 pm 
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plexiglass is somewhat standard for this type of thing. One thing to watch for is it contains water, so you should heat it slowly and allow it to dry or you will get bubbles in it. I guess that also gives you an idea on temperatures. Remove any backing materials before this.

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PostPosted: May 11, 2016, 3:55 pm 
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+1 on the plexiglass.

Depending on your sheet size, or how big of an oven you have, you can heat it in a conventional oven (lower temp setting, and depends on what kind of composition the glass has) to a pliable point, then remove and drop it over a wooden buck.

clamp it to the buck and let it cool naturally. Its best to do it on a fairly warm day (70+°) as it reduces the chances of cracking or splintering while cooling if the buck is a closer temperature to the material. I want to say the pliability point of plexiglass is somewhere around 200° but don't quote me on that.

alternatively, if you are using thinner stuff.. a quality heat gun will do the trick. Form a buck, lay plexiglass over and heat until the plexiglass takes the shape, with gentle pressure of course.

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PostPosted: May 11, 2016, 4:18 pm 
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yeah i have bent plexi before but nothing with a large radius. i was hoping to bend it around a 2 or 3" piece of pvc that is clamped down.

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PostPosted: May 12, 2016, 1:22 am 
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ABS is easy to come by, and if the thickness is a modest proportion of the radius (like 1/4" or less for a 3" radius) it'll form nicely when heated. The problem with ABS (and most other plastics) it it expands a bunch when heated so it's easy to get potato chip shapes if you're not gentle on how much you heat and how drastic the gradient between heated and non-heated sections. But steel/aluminum pipe/tubing will probably serve you better than PVC for your molds...PVC gets soft when heated too,

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PostPosted: May 12, 2016, 2:33 am 
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A buddy of mine make aircraft AC systems and he uses ABS types of plastics. He heat the sheet in an overhead infrared oven and then lowers it onto a wooden buck on a vacuum table. Works slick.

Tom

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PostPosted: May 12, 2016, 8:56 am 
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JackMcCornack wrote:
ABS is easy to come by, and if the thickness is a modest proportion of the radius (like 1/4" or less for a 3" radius) it'll form nicely when heated. The problem with ABS (and most other plastics) it it expands a bunch when heated so it's easy to get potato chip shapes if you're not gentle on how much you heat and how drastic the gradient between heated and non-heated sections. But steel/aluminum pipe/tubing will probably serve you better than PVC for your molds...PVC gets soft when heated too,


and releases nasty smelly stuff!

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PostPosted: May 12, 2016, 9:21 am 
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Does it need to be a large radius? A sharp bend can be made in Lexan using a press brake. Maybe up to .093 thick? There is no need to heat it. it might work in a box brake too.

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PostPosted: May 12, 2016, 10:19 am 
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I don't have access to any type of brake and i would like the radius to match the rear hoop radius. i think i just need to try a few things scrap lexan and abs are easy to come by and are cheap. it would be nice it my vacuum former was 2" larger ; (

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PostPosted: May 12, 2016, 3:32 pm 
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mjalaly wrote:
I don't have access to any type of brake and i would like the radius to match the rear hoop radius. i think i just need to try a few things scrap lexan and abs are easy to come by and are cheap. it would be nice it my vacuum former was 2" larger ; (



Do it in two have with a flange in the middle that bolts both halves together. Gives it ridgidity, riggiddity Added stiffness also.

Tom

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PostPosted: May 12, 2016, 3:43 pm 
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Off Road SHO wrote:
mjalaly wrote:
I don't have access to any type of brake and i would like the radius to match the rear hoop radius. i think i just need to try a few things scrap lexan and abs are easy to come by and are cheap. it would be nice it my vacuum former was 2" larger ; (



Do it in two have with a flange in the middle that bolts both halves together. Gives it ridgidity, riggiddity Added stiffness also.

Tom


you mean on the vacuum former?

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PostPosted: May 16, 2016, 4:42 am 
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Does it have to be transparent?

If not I would look at Kydex. It is a plastic that is very easy to work with. All molding can be done using a kitchen oven.


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PostPosted: May 16, 2016, 9:04 am 
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i couldnt get it to bend at all using a heat gun. it seems like the 24" bend distance is just way to long and it cools too quickly.

guess its back to making a plug and fiberglass mold.

this is also an option if i can find an oven big enough
http://www.antiqueairfield.com/articles ... rt-trainer

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