DIY Vacuum Forming

[cmittle]

Do not use acrylic it is very brittle and will shatter easily if contacted. Thats even in warmish temperatures, just imagine what winter would do to that. I'd suggest Lexan (aka polycarbonate). Both of these materials are sold in sheets at my local Lowe's. Lexan is quite a bit more expensive than acrylic, but I'd hate to see you get finished go for a drive and have your hubcap explode. Also this would create a hazard on the road if it did happen.

[instarx]

I spent many years in occupational health evaluating and monitoring employee exposures to volatile compounds from plastics and composites, and you don't have anything to worry about when heating plastic in your oven. The temperatures aren't high enough, the amount of plastic is small, you aren't going to do it very often, and the plastic is only going to be brought quickly to temperature - not held there for a long time. There may be be a mild plastic smell, but no health hazard.

It won't ruin your oven, and just opening the door when you are finished will allow any vapor to escape. If you want to be absolutely sure just keep the oven door slightly open when the plastic is inside. I doubt you'll even smell anything - you aren't trying to burn it, just soften it.

[Ford Man]

I use to work at a facility where molded polyurethane car bumpers and body components. The chemical components used to make polyurethane have a warning label stating that exposure can cause cancer. There were several people that worked there that if they were exposed to the raw materials for more than a few minutes would get where they could barely breath. I know several of them were take to the emergency room for these symtoms. I don't want anything like that going into the oven my food is being prepared in.

[Bicycle Bob]

Before vacuum-forming polycarbonate (Lex**) you should soak it at about 190 F for 8 hours to drive the moisture out, lest you get steam bubbles. Acrylic is still used on racing cars. It is on the brittle side, but is manageable. Uvex is probably the best for cheap and tough with easy formability.
For a simple shape like moon covers, you can use free-blowing or even sagging. You can also use a male mold, and drape the hot plastic over it, smoothing it with cotton gloves or rags.
Heat guns are good for controlled bulges; bad for even heating. Ovens can be uneven too - you might want to use some tricks to minimize radiant variations and circulate the air.
Unless you see smoke, the fumes are negligible - anyone worried about their kitchen oven could run it to a higher temperature, empty, to volatize any residuals.

[cmittle]

Originally Posted by Bicycle Bob

Before vacuum-forming polycarbonate (Lex**) you should soak it at about 190 F for 8 hours to drive the moisture out, lest you get steam bubbles. Acrylic is still used on racing cars. It is on the brittle side, but is manageable. Uvex is probably the best for cheap and tough with easy formability.
For a simple shape like moon covers, you can use free-blowing or even sagging. You can also use a male mold, and drape the hot plastic over it, smoothing it with cotton gloves or rags.
Heat guns are good for controlled bulges; bad for even heating. Ovens can be uneven too - you might want to use some tricks to minimize radiant variations and circulate the air.
Unless you see smoke, the fumes are negligible - anyone worried about their kitchen oven could run it to a higher temperature, empty, to volatize any residuals.

I was under the impression that it needed to be placed with a dessicant to remove moisture from the material. I did a little bit of research that indicated this about a year and a half ago when I was drape forming a couple of things. Also I've toured an injection molding facility near my home town a couple of times and I remember they said they have to run the polycarbonate through a dehydrator system for a long time before they use it as well.

It sounds to me like you've done this before so maybe your trick works I'm just not sure that I follow. Could you elaborate?

thanks,
Cory

[my first gmc]

How about heat lamps?

[Bicycle Bob]

Dessicant sounds like a neat process if you have it handy. Much depends upon the humidity where the sheets have been stored. If you live in AridZone"A" the stuff may be good to go. Just test a little sample up to a really floppy forming temperature, and see if it gets bubbles. If it does, bake longer, near but not over boiling temperature for your altitude. Domestic ovens, BTW, all have a vent exiting through one of the top burners.

[Shawn D.]

Originally Posted by Ford Man

The chemical components used to make polyurethane have a warning label stating that exposure can cause cancer.

The key is "components used to make polyurethane." The end product is not harmful.

[captainslug]

If you want to save a good deal of money, check your local phone book for plastics shops. Some sell their off-cuts at $1-$2 PER POUND rather than the full sheet price. If you're making smaller parts this can save you 90% of the cost of the sheet. Just bring a tape measure and have some idea of how much plastic you will need.

I tend to buy 50 pounds of polycarbonate once a year from Piedmont Plastics, Inc. - much more than just sheets, rods, tubes which has many locations in the Eastern US.

[instarx]

Originally Posted by Ford Man

I use to work at a facility where molded polyurethane car bumpers and body components. The chemical components used to make polyurethane have a warning label stating that exposure can cause cancer. There were several people that worked there that if they were exposed to the raw materials for more than a few minutes would get where they could barely breath. I know several of them were take to the emergency room for these symtoms. I don't want anything like that going into the oven my food is being prepared in.

Making plastic from raw chemicals and heating a plastic article are two very different things.

Of course you are free to be as cautious as you want to be, but in my professional opinion the risk of any negative health effects from heating a few ounces of plastic in your oven is near zero. It is about as hazardous as the "new car smell" when you buy a new car - which comes from off-gassing of the plasticizers used in interior components.

And by the way - shame on that company for sensitizing their employees. That does not have to happen.