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Picture of How To Oven Form Acrylic
Or atleast how I oven formed acrylic. A few weeks ago I sent out a file (acrylic flatware) to Ponoko to be laser cut. These are the steps I took to form the flatware into usable shapes. It's very easy to do!

What you need:
Acrylic
Oven
Baking Sheet
Aluminum Foil
Timer
Felt - for handling the acrylic and to prevent scratches
Tools for forming

Tools for forming may include:
a Mold - any object/shape you can press the acrylic into to give it shape
mallet and/or a peen for shaping

Caution, Ive only tried this in an Electric Oven. I cant recommend for gas ovens.

Im forming the flatware and using 2 forks and 2 spoons I already have to shape my acrylic fork and spoon.

I also turned it into a video, you can watch that down below or click through the rest of the steps.


Step 1: Preheat oven to 300 degrees Fahrenheit

Simple enough.
 
Chitaracainz2 months ago

FYI, tonight I oven bent 10mm acrylic. I baked it at 180 Celsius (350 F) for about 12min. I was only putting in a simple bend so I used wood blocks cut at the angle I needed, one for each side of the acrylic plus the cool metal bench to press against. The 10mm bent as a curve rather than a tight angle, which is fine for my project. The inside of the angle has the impression of my wood block! If someone needed a tight angle I suspect thinner acrylic would be easier, or perhaps heat it for longer. As I need the rest of the acrylic relatively straight and one of my pieces has bent a little out of line, I decided not to risk additional heating. ;-)

BoByS5 months ago

Dear Kiki! Thank you for the great tutorial. Definitely will try it.

But I can't understand, how it's possible to be "15 minutes for each 1/43 thickness was the rule of thumb". So you need to put a 1/43 thick sheet in the oven for 15 minutes? Correct me if I'm wrong but if the sheet is thinner you'll need less time. I think it should be 15 SECONDS.

3mm is about 1/84 inch, not 3/253. Your numbers seem to be off, but I'm glad the timing worked for you.

Can you add some links to your references? You say you "heard 15 minutes for each 1/43 thickness", but I can't seem to find good consistent sources anywhere on the internet.

My ruler says there's about 25mm in one inch, so 3mm would be about 3/25ths of an inch.

3mm = .11811 inches
1/84 = .0119047619
3/25= .12
I think the thousandths we're arguing is probably negligible to the heat forming, although I do admit your decimal is prettier than mine.

kiki brown bear (author)  FullofMonsters5 years ago
 Sorry for any misinformation, I'm just a student currently and experimenting for the first time. Thanks for the correction.

I couldn't find any consistent timing anywhere either. I heard "15 minutes" from my professor for the class I was making the flatware for, Doug Bucci. Or you can find his blog here. I don't remember correctly, it was either an answer someone else had told him or he figured from his own experimenting.

I hope that helps.
No worries! I'd just like to learn more about working with plastics in this way and am a little frustrated about not being able to find consistent information. I think the time and temperature varies a bit by manufacturer and other factors, so we'll just have to practice and play it by ear.

Has anyone used a gas oven instead? thanks

I just found this post, and for whatever it's worth, yes — this definitely works with a gas oven. I had set my gas oven to to 300°F and placed two, 12-inch acrylic, translucent-blue tubes (about 3mm thick) on the center rack. They tubes were malleable after about 5 minutes. I used thick winter gloves to remove the tubes and I quickly shaped them by hand, like clay. They were almost hard after 40 seconds, so I would shapes them a little at a time and then place them back into the oven for another 2 minutes between steps. I did this about 3 or 4 times before being satisfied. The acrylic was still resilient enough that if I did not hold it in place, it would slowly try to return to its original shape, so once I was done I quickly dosed it in cold water. During heating there was a smell, but it was not horrible and certainly did not ruin anything, though I would recommend having a window open. I also would not recommend keeping the acrylic in the oven for more than 20 minutes total, as it was starting to melt and fuse to the tinfoil and anything longer could definitely cause greater problems to air quality and the oven.

final product had bubbles from the gaseous nature of the oven :/
I read somewhere that fumes are given off that could be explosive

Tony
C.W.B.913 years ago
Is this method able to be done on a larger scale such as a mold of my on face or something more simple such as a large lense for a mask? if someone who knows could email me at flexo123@hotmail.com or best.casey@gmail.com that would be awesome thanks
BlkDragon963 years ago
Pardon me if I'm being dense here, but are these "safe" to eat off of? Will they breakdown or give off nasty chemicals as time goes on?
Matt94 years ago
Haha, If only.
If only i had found this instructable earlier. Turn's out oven's don't like some of the paper sheeting on the pieces of the acrylic. It also turns out lungs don't like acrylic fumes. It also turns out neither does the oven. Soo in the end i've been poisoned by fumes, particles and now i need a new oven. If only heyy.
: I
jayman13104 years ago
Did it fume out your oven? Is there any smell left afterwards? I don't wanna have cookies that taste like plastic after this...
Nevermind. I tried it. Only a slight smell left afterwards, to those wondering.
panks5 years ago
This is really terrific! I would have never thought of shaping it this way. Have you ever tried cutting it with an xacto knife while it is hot?
kiki brown bear (author)  panks5 years ago
No I haven't. That's really interesting, I've never even thought about it.

Have you tried it, did you get good results?
What kind of felt did you use? It seems like wool-based felts tend produce a bit of lint at times, but I'd be nervous using the acrylic craft felts because it seems like they could be susceptible to melting from the heat too...
kiki brown bear (author)  spiralshannon6 years ago
I used Eco-felt. It's made from 100% post-consumer recycled plastic bottles. Since the acrylic cools down so quickly, the felt isn't heating up very much. In my experience anyway, I never had it on the acrylic for more than 2 minutes and it didn't melt at all. The whole forming process is very quick. If you have any more questions don't hesitate to let me know.
Thanks! I tried it with some wool-blend felt that I had lying around, and it worked out beautifully!
robomaniac6 years ago
Very interesting! Will try it. Thanks! ps- You love orange! :-)
gemznbeadz6 years ago
Thank you so much for posting this informational tutorial. I've been wanting to use Ponoko for a while now, but hadn't thought about forming the resulting shape. I just have one question: as a fused glass artist, I'm used to finding all sorts of concave items to slump glass into. Did you consider putting the acrylic in the oven on top of the fork or spoon you were forming it to?
Plastic, while working SORT of like glass, is done at a state with less "flow". Where you can get glass hot enough to slump into the mold, and get a good form... with plastics, you need pressure, either by hand, or vacu-forming, to get good results. Also, the hot metal will retain the heat longer than the plastic...leading to a much longer setting time, allowing for more chances to make a mistake :-(
I see. I didn't know about the pressure aspect of the forming. Is something made of metal the best to use as a form? What other materials have you tried?
well, for PET (melts at 220°C and it starts to soften at 40°C) I've vacu-formed over pyrex glassware, plaster, and metal mostly. I've SEEN forming done on a buck made with a foam core, and bondo surface. Seemed to work pretty well. One of the problems inherent with "slumping" PET plastics is... if you get them too close to the melting temperature, they go brittle.
rivetgeek6 years ago
this would work a lot better with color pictures.
kiki brown bear (author)  rivetgeek6 years ago
The images aren't very good because they're stills from the video. I thought I would just highlight what I'm trying to show by desaturating the rest of the image. I'll upload full colors ones.