Oven temp to bend thin acrylics?

[Anonymous]

If I were to get brave enough (read: permission from the chef) to try baking up some acrylic into custom shapes whats a good temp to set the oven to?

Also, would it be good to try and add some humidity to the oven (a can of boiling water) or is it best cooked dry?

I imagine different temps might be best for different thicknesses and if so I sure would appreciate a little more info on what temps different thicknesses should have.

(And no, this isn't for anyting commercial, I'm not even sure I'll try what I'm thinking.. - Custom-shaped overflows..)

Thanks!
Norm

 

[Anonymous]

You need James or Fergy to chime in and answer this one. I will be interested to hear what there answer is.

Louey

 

[Anonymous]

from what I've been told, acrylic off gasses an explosive gas when cooked, that is why all ovens for that use are electic based. I've cooked it in my gas oven many times (before being told about the "explosive gasses"), I always used the lowest settings with pretty good success. Too hot and you'll get bubbles (which can look cool though, nice textures)

 

[Anonymous]

It is true that most thermo plastic will give off dangerous gases when heated above certain temperature, and it is not recommand to use kitchen oven for bending due to possible overheating.

I use a heating stripe I brought from an acrylic supplier to make acrylic bend. It allow a small strip area to be heated, making the bend clean and professional.

Commerical acrylic oven is a large walk-in container for bending bull-nose and other complicated shape, as well as for annealing the plastic. It is never use for making a simple bend.

Beside the danger of fire (acrylic fire is very difficult to put out, and it gives off very nasty fume when burnt), heating the whole panel also make the plastic very difficult to work with. It may not be an issue about optical distortion with overflow, but there are so many issue with it that I strongely against the use of kitchen oven.

You either buy it ready-made, or use several separate flat piece to glue into a box, or get a heating stripe for acrylic.

With that said, the temperature to heat acrylic depends on the molecular weight. Casted acrylic has a higher molecular weight than extruded. You need slightly higher temperature for higher molecular weight. For bending, you need somewhere between 100C-170C. Thicker sheet need slightly higher temperature unless you are heating it from both sides. Do not go above 170C for extruded or 190C for casted. It will bubbles.

For reference, any flame with temperature higher than 300C will cause acrylic to burn, and without any presence of flame, acrylic will self ignite around 460C. Try to remember this fact if you ever smoke while sanding acrylic with a motorized sander

 

[Anonymous]

Hmmm... With that info I'm not sure it's a good idea if the chef reads this thread..


Thanks for the info!

 

[Mihai]

How about a heat gun? That should localize the heat and give you better control...

M.

 

[Anonymous]

Heat gun makes a broad heating area, and the forced air make it worse. Unless you want to make a dimple, it is not going to be useful for bending.

You need heat as IR, not hot air force out of a nozzle.

However, heat gun can be used to bend small acrylic rod....

 

[Mihai]

I was thinking of moving the heat gun from left to right along the line where you want the bend in. Not that I tried (I didn't), I just thought that it might work.

M.

 

[Acrylics]

for small pieces, set the oven at about 300-325F and have an oven thermometer in there to be sure as standard built in over thermometers are notoriously bad. Actual forming temp is usually 270-290F depending on material.
Place the piece on a cookie sheet or similar so that if it overheats it will not drip into oven element. 1/4" should take 5-6 minutes and pick up using a spring clamp or oven mits.
Contrary to others' experiences, I always do thicker material at a lower temp to get it to heat more slowly and evenly, thicker material is expensive so go slow or you'll fry it.
Also contrary to others' experiences, commercial ovens can be either electric, IR, or gas, and these explosive gasses are not really common as such, it's more the monomer vapors that are released that can cause dizzines, nausea, vomiting, etc in some people, so keep the windows open and a fan going in case you're sensitive to this. If the smell of cutting acrylic really bothers you - don't try this at home.
It is best to cook dry as one of the reasons acrylic fries is the moisture in the material itself.
Heat guns can work, but not necessarily very well at doing line bends. You can buy a heat strip or make your own strip heater for a few bux.

HTH,
James

 

[MonKei]

I have used a heat gun to bend acrylic. it seemed to work well.. trick I used was to lay the acrylic over some flat surface with a strait ledge (workbench, counter, chest freezer, etc.) place a piece of wood (2x4 or something strait and flat) or something that wont burn like that along the bend line, the bendline you want being right over the edge of the work area... hold the wood in place using your hand (wearing yardwork gloves to sheild from heat) and heat with gun moving back and forth along your bend line, when the plastic warms up to the bending temp, it will start to droop and you should give it a little push down to see if it will bend down some more, continue heating/bending until you get the bend you want and voila, if you did it correctly, you should get a nice clean strait bend.

 

[Anonymous]

Outstanding, thanks James, MonKei!

 

[Fl_Seagull]

I have found clamping the material between two wood paint stirrers work well.

http://reefs.org/phpBB2/viewtopic.php?t=50433

 

[RobinsonFam1]

i have used heat guns for bending alot of acrylic into some hard angles. it can be done with time on your side. i have never had any problems or burns or bubbles.