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Molding Thermal Plastic
- Thread starter nobbie48
- Start date
Not a bad intro. He didn't get it hot enough. For most plastics as you start to heat, they will ripple, as you continue to heat, the ripples disappear, then you pull. His 1" thick steel around the outside pulls tons of heat out of the plastic. I would make that differently (angle iron instead of solid bar) and/or preheat. If possible a vacuum accumulator helps a lot too to get a good pull. I did this for a few years in a past life. Be careful what plastic you are heating as some give off nasty vapor (acid).
For that small a part I would use a cheap toaster oven, maybe one shared by a DIY powder coater. The temperatures would be more consistent. I've bent plexi with hot air and it's too easy to over heat.
The other issue is the grid pattern left by the screen. It might not be desirable. Considering the price of tupperware for older bikes it's a good starting point.
If you want to pull parts that big, you definitely need a lot of changes to that rig. For most parts, the flat on the bottom where the screen is is waste anyway. You need your mold to have the surface finish you want and you don't worry about the off-cut. We made parts up to 4'x8' with ~3" draw (easy if you can get the sheet to heat evenly) and 3'x6' with an ~24" draw (those ones were a prick).
A battery cover for an old Goldwing came to mind. They flew off and got run over. I see originals for hundreds of dollars but there are reasonably cheap fiberglass copies. Like most things the complexities expand exponentially with size and experience can be an expensive acquisition.
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