Couple questions about vacuum forming

[thewise1]

1. How long do I heat the plastic for? (how long does it take to sag 2 inches
2. How hot does the oven need to be? (preheated)
3. How long does the home vacuum need to be on? (how long do I leave the plastic on while the vacuum is on)
4. How long does it take the plastic to dry (polystyrene)
5. What paints do I use to get a glossy surface (I plan to use krylon fusion)
6. Krylon fusion says I don't need to sand the plastic or use primer. Just spray on. is this true?

[nevermind1534]

5. What paints do I use to get a glossy surface (I plan to use krylon fusion)
6. Krylon fusion says I don't need to sand the plastic or use primer. Just spray on. is this true?

The fusion should work fine. And you don't want to use a primer with it. You only use the plastic primer for paints that aren't made for plastic.

[thewise1]

Ok, what about sanding. And do they have colors that come out glossy or do they have a krylon gloss that you add to any outer layer of their paint.

[vskid]

Ok, what about sanding. And do they have colors that come out glossy or do they have a krylon gloss that you add to any outer layer of their paint.

No sanding required, at all. The fusion comes out kinda glossy. You can use clearcoat if you want more gloss and some protection. More on paint in this thread.

[bacteria]

1. How long do I heat the plastic for? (how long does it take to sag 2 inches

About 2 mins, once the plastic starts to sag it drops quickly, you need to watch.

2. How hot does the oven need to be? (preheated)

About 200-220 celcius is ideal.

3. How long does the home vacuum need to be on? (how long do I leave the plastic on while the vacuum is on)

I turn the vacuum cleaner on a few seconds before putting the plastic on; and leave it for about 6 seconds whilst plastic is in place and formed; then leave for about 10 seconds more, when plastic is starting to harden but still supple, and carefully remove mold.

4. How long does it take the plastic to dry (polystyrene)

A couple of minutes to cool - doesn't need drying as it is already dry and very hot out of the oven!

5. What paints do I use to get a glossy surface (I plan to use krylon fusion)

Krylon Fusion, or Plasti-Kote (which I use as I can't get Krylon in the UK). Plasti-Kote is excellent; and also has a very good plastic primer spray paint too.

6. Krylon fusion says I don't need to sand the plastic or use primer. Just spray on. is this true?

Depends on the surface - if it is smooth, then spray paint will not stick so well, so always best to use a primer - not worth not doing. If the paint however says you don't need primer, fine; but test on a spare sheet you can waste to see if it is ok; different plastics may need primer anyway - if in doubt though, use primer.

[thewise1]

Thanks bacteria, a little inclear on the vacuum though. Let me see if I have this right:

1. turn on vacuum a few seconds before plastic
2. place plastic on
3. turn vacuum off after 10 seconds

Is that right?

[Tibia]

Never use primer with Fusion. It will still work, yes, but it's not letting the Fusion work the way it's supposed to. Fusion will actually bond with the plastic. If there's a layer of primer there, it can't bond. It'll still be a skin of paint, but it's not bonded to the plastic like it normally would.

If your surface is too glossy, a very light sanding with very fine sandpaper will make the surface take paint much better.

[bacteria]

Thanks bacteria, a little inclear on the vacuum though. Let me see if I have this right:

1. turn on vacuum a few seconds before plastic
2. place plastic on
3. turn vacuum off after 10 seconds

Is that right?

Yes.

Have some spare sheets; when I did a batch a while back I got about 75% success rate, which is quite high; get double the sheets you need, to be safe.

Interesting about the spray paint in question not needing primer.

[thewise1]

Good that they come in packs of 8 and I only need 2. Plus it's only $10 nice.

[thewise1]

Alright here's another thing, the only thing so far that I can't seem to figure out is how to make the screw posts. Like how to hold the 2 pieces of plastic together. Any ideas?

[ShockSlayer]

you can buy them at your local Lowe's, or home depot, or any hardware store.

SS

[collinE]

You could buy them like SS said, but why do that when you can make ones that don't look as good and waste tons of time? :

I like recycling screw posts off cases by cutting them off with a dremel and ABS cementing them in. You can use the original screws that way, too.

I've seen cutting the styrene into little squares, stacking them high, and gluing them together (you could use a wasted sheet that didn't form). Once a little column is made, you can drill a hole through it, then glue that into your case.

You could use bac's way by putting plastic around the inside like his psone but that can mean having a deep hole to follow down to where you screw it in.

and I'm sure there's tons more, but there's three main ones that I know.

[bacteria]

I like recycling screw posts off cases by cutting them off with a dremel and ABS cementing them in. You can use the original screws that way, too.

Crap, wish I did that on my IntoPlay; idea is so simple too - I couldn't buy small screws with nuts so had to use a precise hole cut in perspex, which gives way if you aren't careful. Using the screws and plastic shafts in joysticks and securing them to the perspex perimeter in a case is the right method - don't know why I didn't think of that!

[XCVG]

When handling hot plastic, be sure not to wear gloves or oven mitts.

[Mario]

I like recycling screw posts off cases by cutting them off with a dremel and ABS cementing them in. You can use the original screws that way, too.

That's what I did in my portable. I used screw posts for the N64, the controls, and the back panel. So useful! ^_^