POT: Acrylic Bending Jig

Possibly OT. Excuse the x-posting, but there doesn't seem to be one group for this stuff.

I want to bend some Acrylic, so I plan to build a jig. (Too much free time) The plan is to use a couple of knife hinges to separate (1") two pieces of particle board (insulated). I will place some NiChrome wire (2') between the two boards and heat it up with a 24V transformer and a light dimmer. Once the Plexi is warm enough, I'll move my hinge to the desire location and clamp it off.

Has anyone attempted something similar? Should I clamp the Plexi on both sides of the hinge when bending or do I need to allow one side to move, to prevent cracking?

Reply to
Bill Stock
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"Bill Stock" wrote in news:O snipped-for-privacy@rogers.com:

Forget the putting of the nichrome between boards(you wanna collect insurance?)

I'm going from memory, but I believe the book "This Old Boat' describes what you are doing. I don't remember it saying to clamp both edges, but I suspect that has more to do with the size of the piece than anything else. Take a look at the book, I have tried many things from it and all have worked, I don't see why that project would be any different.

Reply to
Didereaux

A simple, not-very-expensive option is to use heat tape which warms the plastic enough for the bend. Take a look at:

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(If the link is broken, to to
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and search on "Plastrip heater".)

Alex

Reply to
Auerbach

Bending acrylic is fairly simple but toaster wire at 24V might not give you enough heat. At the plastics shop I worked at they hat a kluged strip heater like you describe but it had a cal rod heating element running at

220V about 3 or 4 inches from the plastic.

Try setting up some bricks about an inch apart and then take some foil and wrap it around the bricks so it will droop in the middle to make a reflector.

For the heater coil, take your ni-chrome and coil it around an 1/8 inch rod and when you have a coil tightly wrapped about 3/4 of the length of the piece you will be bending. Remove the core and stretch out the coil to length. You can try your transformer, but I suspect you might want to run this at 110V. It kind of depends on the size and of the wire and the length. If it glows white you have too much voltage, or too short of a length.

You might also want to dry out the plastic prior to forming. Acrylic absorbs moisture that will cause a rice crispies effect as the plastic softens. We had an oven where we would dry sheets overnight at about 150F with air circulation.

Good luck.

Reply to
Roger Shoaf

Much safer:

Reply to
CheezWiz

I fear you won't get enough 'heat' that way.

I did a fluted ashtray 6" or so - and I warmed it in a small bench top kiln. The acrylic was rubbery long enough to get it into the bottom and top clamp.

Temp isn't the story - heat or calories is.

Martin

Reply to
Martin H. Eastburn

Not quite like that, I clamped up some in the bench vice, then heated with a hot air gun, then bent it around some wooden forms. It worked reasonably well. It helps to have an assistant (SWMBO) and leather gloves for all.

Barry Lennox

Reply to
Barry Lennox

Fri, Dec 3, 2004, 6:14am (EST+5) snipped-for-privacy@here.not.there (CheezWiz) put out: Much safer:

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But pricey. I got a little ceramic heater, the type with a fan, and it oscillates, for about $19-20 at K-Mart. Screwed up and had it pointed at a telephone, about 16" away from it, and it on only half powr

- softened the plastic enough to change its shape.

Or, if you want to go even cheaper, try borrowing your wife's hair blower, bet that'd work too.

JOAT Be who you are and say what you feel, because those who mind dont matter, and those who matter dont mind.

- Dr Seuss

Reply to
J T

If its a pipe you're bending, you can fill it with sand before bending it, this will stop the pipe from getting kinks once bent.!

Reply to
Happy'Cam'per

Made many tables and plotting boards with bends using a heat gun, the oven in your kitchen works well too if the pieces will fit.

Reply to
Beecrofter

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Reply to
jack

Thanks Roger,

I've been looking for a detailed 'how to' for one of these gadgets, without too much luck. It seems most people use a car battery or a Variac for the power source. Neither of which I have laying around. The other big unknown is the wire guage/ohms as you indicated. I was considering 36 guage, but I suspect it won't generate enough heat. At least the wire is cheap enough for experimenting.

Reply to
Bill Stock

you might try contacting euclid, who make resistive elements for kilns.

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can tell you how much you need at what gauge at what power to produce the heat that you need. they're very helpful if you give them a call and talk to them directly. they may also have what you need in stock.

regards, charlie cave creek, az

Reply to
Charles Spitzer

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> But pricey. I got a little ceramic heater, the type with a fan,

How'd you know I was a cheap bastard? :) Yes, I thought the $50 was a little spendy, but the big problem is that these guys use UPS. Since I'm north of the border, it would be more like $100 by the time they're done with their gouging. Besides, they're on strike up here now.

I considered the blow torch route, but the idea of standing there for half an hour breathing monomers or getting impatient and burning the plastic didn't turn me on.

Reply to
Bill Stock

if you go to your favorite thrift store and buy an old toaster, hair dryer, or electric grill, you'll get nice heating elements, properly sized, really cheap. Put them in series with a lamp dimmer so you can control temperature.

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Reply to
william_b_noble

Fri, Dec 3, 2004, 10:15am (EST-3) snipped-for-privacy@nowhere.com (william_b_noble) says: if you go to your favorite thrift store and buy an old toaster, hair dryer, or electric grill, you'll get nice heating elements, properly sized, really cheap. Put them in series with a lamp dimmer so you can control temperature.

Or maybe just put a big cardboard box over the whole project, or tent it, to keep the heat in. Be best to keep a close eye tho, to make sure you don't set it all on fire.

JOAT Be who you are and say what you feel, because those who mind dont matter, and those who matter dont mind.

- Dr Seuss

Reply to
J T

Some data to help you calculate what you need:

Reply to
J

I bought a strip heater from a local plastics shop, and they had instructions on how to mount & hook it up. It was about 15 years ago, and I don't think I still have the info, but I've got the heater still mounted on a board with fiberglass felt insulation. Just plug it in, wait a bit & bend.

The heater is a flat flexible woven sort of thing, about 30" long. It probably doesn't draw more than a few hundred watts. It's mounted in a groove between two pieces of the felt covered in aluminum foil. No Variac required. It takes about 5-10 minutes to warm up enough to bend

1/8" plexy, but it's always worked nicely. I don't recall trying to bend anything heavier, but I think it will work up to 1/4" if you are patient.

Doug White

Reply to
Doug White

Thanks, very useful.

Reply to
Bill Stock

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