View Full Version : whats the best way to heat and bend plexiglass or lexan?


CHOPMERC
08-16-2007, 04:58 PM
hey guys, i'm gonna be putting a plexiglass or lexan back window in my 51 ford victoria...the car is chopped 5 inches, and i want to retain all the rubber (new rubber of course) and install the plexi just as the glass would be installed, but i'm wondering the best way to heat and bend it...i've heard that lexan would be the better choice because its less brittle....any suggestions?

chaddilac
08-16-2007, 05:24 PM
I've heard of using a heat gun, but leave the protectant on it while doing it... Sorry that's all I got!

aabbcco
08-16-2007, 06:00 PM
I looked into doing the same thing for a project I was working on - I ended up using polycarbonite - the same stuff used for the divider in cop cars - it bends easily w/o breaking or heat, but does cost more and is softer (scratches easier) than plex - but it takes a lot to break it.

A friend told me one way is to build a shape template out of dense insulation foam, cover it and shape it w/ drywall mud/plaster and either use a regular oven (I'd find a salvaged one) to heat it to form to the shape or build your own out of hardy backer/cement board if the part is too big. If you go to a plastics supplier, they can give you tips on temps vs thickness vs cook time - I would plan on some experimenting starting with low temps and long cook times to avoid blistering/warping of the material - and have a extinguisher ready just in case. This was too much effort for my project and thats why I went to the polycarbonate.

RopeSeals???
08-16-2007, 06:07 PM
The homebuilt airplane guys do it all the time.
I've heard of using anything from a home oven, pizza oven, or a homemade contraption made with oven broiler elements inside...

The trick is even heat and a good "buck"(I think that's what they call the piece that the Plexiglass part lays on in the oven)

See if you have any local EAA(experimental aircraft assoc.)chapters near where you live, they should be able to help.

squirrel
08-16-2007, 06:13 PM
hint: polycarbonate IS lexan, or rather lexan is one brand of polycarbonate.

THe kids hate plexiglass on their robots because it shatters, they only use polycabonate. And poly will bend without heat, but tight bends are easier with heat. It will bend a long ways before it takes a set.

Vorhese
08-16-2007, 06:16 PM
I've used a heat gun on 1/8 and 1/4" acrylic many times with good results. I usually build a wood (MDF) jig.

CHOPMERC
08-16-2007, 06:24 PM
hint: polycarbonate IS lexan, or rather lexan is one brand of polycarbonate.

THe kids hate plexiglass on their robots because it shatters, they only use polycabonate. And poly will bend without heat, but tight bends are easier with heat. It will bend a long ways before it takes a set.

squirrel, i think the consensus is to go with lexan...but, the 51 vic has some sharply rounded corners and i planned on using the original rubber to hold them in...do you think some light heat from a heat gun will be adequate to get these pieces to hold their shape??

squirrel
08-16-2007, 06:25 PM
probably depends on how thick you use. You might try experimenting with rolling the lexan over your leg or something else round to try to get it to bend "cold".

old beet
08-16-2007, 06:26 PM
Maybe clamp the new pieces to a stock window. That will get you pretty close. Use a hair dryer, they will take shape..........OLDBEET

CHOPMERC
08-16-2007, 06:31 PM
thanks guys.....

CURIOUS RASH
08-16-2007, 06:38 PM
I've bent it with an actual heat gun before. I wonder if a hair dryer can do it what will happen in the sun.

We bend the stuff at work all the time but we eaither use a sheet metal break or the vaccuum former.

I think an important part to shaping it will not only be even heating, but even cooling.

hotrod1940
08-16-2007, 07:18 PM
probably depends on how thick you use. You might try experimenting with rolling the lexan over your leg or something else round to try to get it to bend "cold".

Won't bend cold, takes at least 350 degrees to shape to full mold. Sharper degree bends can be done with a heat strip. Talk to a sign face manufacturer if you can find one in your area. Molds should have 15 degree slant to get it to release from the mold. There are a couple of tech articles under vacuum forming in the search, I think.

Wild Turkey
08-16-2007, 08:20 PM
Good advice above.

Polycarbonate (Lexan, etc) is the shatterproof version. Take a sharp knife to the edge of a piece and you can shave a sliver off like a piece of hard wood.

Acrylic (Plexiglas, etc) will chip instead of cut.

Trick is to heat the area you want bent without getting any one spot too hot. Direct flame is NOT a good idea.

A buck or other form to bend it over is a good idea -- when it gets to bending temp it is very soft.

For a sharp bend I'd try a piece of metal bent to the shape needed (dont forget to allow for the thickness of the material being bent:rolleyes: ) Heat the metal and let it heat the plastic.

Another problem is keeping the viewing area flat to avoid distortion. Another reason to consider a buck to support the middle while bending the ends.

Good luck!:cool:

thecarfarmer
08-16-2007, 09:04 PM
One thing to watch out for; you can boil the water in it (yes, it absorbs a little) if you heat it too quick. Been there done that.

More:

http://www.portplastics.com/architect/page22.html

-bill

J'st Wandering
08-16-2007, 09:33 PM
I bent plexiglass for the front windows in a camper. I laid the plexiglass on a rug and heated it with a heat gun. I used one of those point and shoot thermometers to monitor the temperature. I do not remember what the magical temperature is but you hit a temperature where it gets soft. Then bent the plexiglass to where you want it and hold it there for a bit while it cools. The first one that I did did not get a nice curve to it but the second one worked out well. Trick is to get the heat spread out evenly. I used 1/8 inch thick plexiglass. Neal

testpilot
08-16-2007, 09:52 PM
hey guys
here is a cheap tip for the heat gun try a wagner paint stripper gun AT home depot