One major problem with a manual pump is the time required to create a full vacuum. A shop-vac will create much more than sufficient suction for molding cases. In my case, vacuuming in a Canadian Winter, I had little over 20 seconds to take the heated plastic out of the oven, out the door, gently place it over the mold (vertically downward over the weatherproofing seal, being careful not to stretch it) and turn the shop-vac on before it solidified and became unmoldable.

I suppose this is for a warmer climate?

Not sure about the climate issue, unless Canadian plastic adapts its thermoforming temperature to the climate.

How thick was your plastic, and what was the shape like? Was there fine detail or deep draw?

In my experience, high vacuum gives you about 2x or so improvement in resolution, approaching the thickness of the plastic, so you get about 4x as much "information" showing. (Actually better if you form into a female mold, so that the mold side is what shows.)

It sounds like you must have been forming reasonably thick plastic, or you wouldn't have had 20 seconds before it cooled too much.

The time to draw down the tank isn't a big deal if you're doing one-off case work, and you don't use too big a tank. If you're doing production work, you want a reasonably serious vacuum pump to draw down your tank in about the same amount of time it takes to heat the next piece of plastic.

(BTW, Doug Walsh has a good deal on surplus 4.5 CFM vacuum pumps at www.build-stuff.com right now---less than $100 shipped---so even a high-end setup isn't horribly expensive. The plumbing and a big tank cost less than the pump.)

I was using 0.060" Styrene. Rather thin. But if you say your method works, I'll accept it, as long as you have personally performed it, which by the looks of your tutorials, you have.

Yes. I've built several vacuum formers and formed a variety of materials, from .030" styrene and textured acrylic diffuser panels to 1/4" PVC and 3/8" EVA foam.

Here's a new video of the good fast cheap kitchen-oven setup in action:



(The youtube version looks better:

http://youtube.com/watch?v=hGBRiYhxRTM

but I don't know how to embed it on a phpBB.)

That's great. I like the idea of the guide posts, don't know why I never thought of that.

How did you get your mold to release so easily? I coated mine in a layer of silicone grease but it still got vacuumed on and I had to drill into the wooden mold and stand on the plastic, pulling on the screw in the hole i drilled, in order to remove it.

Wow! I saw the youtube movie three posts up now, and I think I can actually do that! All he has is a shop vac and a table right? I figure if I make the table on the front page of this thread and use his frame and guide I can vac form a case!

EDIT: What about this vac, will it work?

http://www.lowes.com/lowes/lkn?action=p ... lpage=none

DON'T go buy a shop vac for vacuum forming. Shop vacs are way overrated for vacuum forming, and if you're going to spend money on something that sucks, it's better to put it towards a real vacuum pump. (A vacuum pump can pull several times harder than any vacuum cleaner.)

(Doug Walsh is selling nice vacuum pumps for under $100, shipped, as I write this, at www.build-stuff.com )

Shop vacs these days aren't any more powerful than good household canister vacuums. They're just bulkier because they suck the air through a big bucket. Both are limited by the amps you can pull on a normal household 120V circuit.

You can get a great vacuum forming vacuum cleaner for $5, or maybe $2, if there's a Goodwill Outlet Store (a.k.a. Blue Hanger Store a.k.a. The Bins) near you.

Look for a high amperage (10 or 12 amps or more) or high wattage (1200 watts or more) canister vacuum. (The wattage or amperage will usually be printed on a sticker or formed into the plastic near the place where the electrical cord comes out.)

I usually use a little 1000-watt Shark hand vacuum, which pulls harder than my 5.5 HP shop vacuum.

Shop vacs can pull a lot of air against little resistance, but they don't really pull all that hard when it counts. (When most of the air has been pulled out---which any vacuum cleaner can do---and you need to pull HARD to get good detail.)

I don't have any wood working tools so anyone have tips on working with clay?

Every time I try to make a mold it ends up shrinking. I tried making a large slab and then just sanding it down to the right size, but it cracked too much while drying.

Any other materials I could use besides wood?

What's the best product to use to lube the wood?

Your mold will shrink a little with clay. You need to make it to size, let it dry, then add more clay as needed, let it dry, then once more. Also, the more water in the clay the more it will crack. Also, the thicker the mold the more likely to crack (I found this out).

Look at my guide if it helps.

I just found a very educational guide to vacuum forming. It's written more toward large-scale manufacturers, but the information in this PDF is very useful. If you're researching what vacuum forming is and how it's done, then read this. It also gives great information about things to keep in mind when making your mold, such as draft angles. It even has a list of advised temperatures for melting your plastic. Very useful!

PDF link

Sigged

That sounds wrong on sooo many levels.

Edit: Great guide from Make Magazine's Kip Kay


http://www.metacafe.com/watch/1251365/m ... uum_former


http://cachefly.oreilly.com/make/vacuum_former.pdf

0.08 cm seems so thin! Is this thick enough for structural stability for an entire case, or do you usually have an internal frame that holds the components?

you can add a frame if you want, but I found as long as you don't use a mold that's too tall, then it won't stretch enough to make it flimsy.

Is there another site that sells .80 cm Polystyrene sheets? Since the site link in the op doesn't work.