DIY Vacuum Forming

[Indie]

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.

This is EXACTLY the info I need. Am trying to VF .030" polycarbonate sheets and was getting these D@@n bubbles. Had me scratching my head. I never would have thought of steam bubbles.

Thanks. It is very much appreciated.

Indie

[aerohead]

Originally Posted by cfg83

Hello -

Thanks for the advice. Since the operative word phrase "if you're doing it right" is in play, I don't think I will try it with our oven. I need room to make mistakes. I would need to find another way to achieve the same thing.

CarloSW2

An insulated metal box with ceramic lamp holders and heat lamps can bring a thermoform sheet,as ABS up to it's yield point,where it begins to sag and ready for forming.------- A local shop would secure the sheet to a frame.When ready,the frame was quick-clamped ( all air-ram driven ) over the form and onto the vacuum table.A simple foot-actuated valve enabled vacuum from a large accumulator to communicate with the table,drawing the part down over the perforated pattern.--------- The perforations were very small and prevented any of the material to flash into the voids.------- Within 30-seconds they de-clamped the part and sent it to a trim station where a router,following a trim fixture template cut away any superflous material.------------ It's pretty amazing to watch.You could pull a part the size of Jeep front end in a single piece!

[Bicycle Bob]

For casual use, even drywall is rated for vacuum forming temperatures. A bit of metal shielding around the heaters should be all you need. Old stove elements make good heaters - running at 120 V they don't glow. The most important thing is to put a fan inside the oven, with the motor outside, to get even heating. Another neat trick is to use a length of I-beam drapery track extending out the door of a narrow, tall oven. You can use cheap paper clamps and drapery rollers to suspend a sheet or a frame, and then slide it out into position for drawing. The clamp can be hinged from the bottom of the mold.

[Vekke]

I started manufacturing my own "small" 720 mm x 720 mm vacuum farming table. Vacuum box is now ready and glues are drying. Now I will start making brackets for holding that plactic sheet.

vacuum forming table box.jpg - Windows Live

Hole spacing is 50 mm and size 2mm for each hole. My subcaontractor advised to use 1 mm holes, but those are too small for my drill :/.

[Vekke]

First test piece tried out with bad luck. As you can see from the pictures i tried to meld the abs outside and it was -3 celsius. With that fire heater I was only able to melt about 400mm soft enough. So when I placed that plastic sheet to my vacuum forming table I did not get no suction because the abs did not touch the table. Also the "tool" was sucted inside with regular 1400 watt Volta vacuum cleaner.

DIY vacuum forming heater.JPG - Windows Live

Next stage is to build proper heating system that I will get that full abs sheet soft and try again...

[Bicycle Bob]

In the description of my oven set-up above, it is not explicit that the mold flange is also vertical, to receive the hot sheet with a minimum of fuss and delay. When I was in the biz, we made our oven from sheet asbestos and aluminum angle extrusions. Now, you'd get 'glass reinforced sheets of concrete instead, but I think that drywall and corner bead would do the job well enough.

[2TALLTARY]

You shouldn't have a problem heating lexan in your oven but you should also try a heat gun. It might take a little longer but it should work. I found a some data sheets that might help at iplasticsupply.com and hightechplastics.com