Vacuforming question

[Mr. Nagata]

I've been dabbling with vacuforming for a couple of upcoming projects. Basically, I built a very small table attached to a shop-vac and have been heating the styrene with a heat gun. Works fine for small stuff.

I'm hoping to build a slightly larger table now, but the frame/media will be too large to heat evenly with a heat gun. I've seen folks put the frame in the oven. But how long do you heat the sheets and at what temperature? And is there anything else I need to know?

 

[CustomCreations]

http://www.crclarke.co.uk/Support/pdf/thermo.pdf

Its a really good document to read through, I used to teach vacforming ;-)
Main thing I learned is the plastic should be bouncy rather than saggy, before forming. If its saggy it can cause webbing.
I think the temps are mentioned in the article for slump molding.

Most of your questions are answered in the PDF, just go slow. Plastics 'window' for heating is very narrow, so it reaches its working temp very quickly.

D

 

[jackdoud]

You need to watch the sheet as it heats. It will initially sag then tighten up. When it sags the second time that's when it's ready. The amount of sag you need depends on what your forming and the thickness of your plastic so it takes some trial and error.

Different plastic takes different temps, I usually go for around 400*F when forming .08 HIPS

 

[kimncris]

My frame is very small because our oven is ancient, but I just turn the oven all the way up and wait for the plastic to become wiggly. It takes less than 30 seconds on thin stuff so you have to be observant!

 

[Mr. Nagata]

Thanks for the tips. This is really helpful. I notice on that document that the plastic window for styrene is roughly 225 to 300 degrees F. Does that mean the oven should be set at that temp, or should it be set higher?

Also, how far does the sheet sag? I'm sure it depends on how big/thin the sheet it, but should I prop the frame up so the plastic doesn't touch the over rack?

 

[stormtrooperguy]

wow, that's a great pdf. very cool, though i confess to only understanding portions of it.

 

[jackdoud]

Also, how far does the sheet sag? I'm sure it depends on how big/thin the sheet it, but should I prop the frame up so the plastic doesn't touch the over rack?

Yeah, it depends on how big the sheet is. My table's 10"x9" and I usually pull with .75"-1" of sag. A large sheet can have 3"-4" of sag or more depending on how soft you want the plastic. You have to be careful as the heating is exponential, as soon as it starts to go you have very little time to pull it out. You definitely need to have something protecting the heating elements.

 

[Skaught]

When I've done it in my kitchen oven, I know it's ready when it ripples slightly when tapped. I've done it in my stove fully closed as well with a larger frame sticking out slightly. The part sticking out I heat gun.

Scott

 

[deck5]

Thanks for the tips. This is really helpful. I notice on that document that the plastic window for styrene is roughly 225 to 300 degrees F. Does that mean the oven should be set at that temp, or should it be set higher?

Also, how far does the sheet sag? I'm sure it depends on how big/thin the sheet it, but should I prop the frame up so the plastic doesn't touch the over rack?

I balance the frame on upside-down drinking glasses.

 

[Celtic Demon]

I balance the frame on upside-down drinking glasses.

Thanks for the info! Was wondering how people did this!

 

[Smiling Demon]

Or, you could just make your frame fit your oven so it slides in just like the racks. Just remove one rack from your oven and slide in your frame!
No balancing act needed!

 

[deck5]

Or, you could just make your frame fit your oven so it slides in just like the racks. Just remove one rack from your oven and slide in your frame!
No balancing act needed!

I did one like that, but found I had to be too careful that the plastic didn't come especially close to the edge of the frame, or the proximity to the metal wall of the oven would cause it to melt.