Bacteria's project - making a vacuum forming table

bacteria · Post by **bacteria** » Mon Oct 20, 2008 4:34 am

Updates for today:

Stuck some mounting board on the sides to seal the two layers together, used general purpose glue, then used stacks of flexible silicone bathroom filler to seal any gaps and keep the system airtight.

(top side)

(under side)

Next, cut out a sheet for the vacuum hose to connect to, made a hole in the middle to fit the hose, sealed with general purpose glue, then hot glue; then lashings of flexible silicone filler.

I decided not to do the extra work of making a box base; especially as it would be a good idea to hold the vacuum hose attachment whilst securing it to the vacuum machine; so I simply made two legs and screwed them to the sides of the base, put in a strut and screwed that to the backing piece, screwed in a smaller piece to wedge against the hose and filled with the flexible silicone sealant.

Not much more I can do now to finish this vacuum table off, as I need to give the silicone 24 hours to dry.

I did however buy some white modelling clay, cost Â£3 each. I will use this to make the mold. I intend to do that this afternoon. This will also need probably several hours to dry properly.

Here's something to save me build time - a tin foil disposable oven roasting tray - deep enough and big enough as you see. This will allow me to place the frame in the oven, have it elevated above the oven tray racks, be easy to remove, and allow for the drooping once the plastic heats up. Innovative, huh! Cheap too (about 75p) and re-usable. Given that I have about 20mm between the edge of the mold and the edge of the plastic on the frame, and the height of the system will be about 47mm, each system half only needs to be about 24mm high (plus about 4mm more for the base, wastage), I only need the plastic to droop by about 35mm; which is about half the height of the tin foil tray.

bacteria · Post by **bacteria** » Mon Oct 20, 2008 7:58 am

More progress:

No point wasting most of a pack of the clay for the insides of a mold when it isn't needed, so used an old ice-cream container to bump up the middle.

Cut out about 22mm from the base of the container, as I will have a few millimeters of clay on top; should end up about the right height:

Time to start building up the sides with clay...

Done, just needs to look a bit better: smoothed the sides with an old butter knife.

Time to leave it to dry. When dry, it can be drilled, sanded, painted and varnished (according to the packaging).

Wanted to have a nice groove around the d-pad area and the 4 button PlayStation controls. On the pic below, I cut out some blue card to represent the positions of the PSone screen, d-pad, 4 button pad; the two coins represent the size and position of the joysticks.

Once the mold is dry, overnight; I will give it a good sanding to end up with the final item.

Now you can see the mold, you get a good idea of what the idea I had for the casing.

Modeling clay is easy to work with. I found touching a pen end in water and then making the circle on the mold works nicely.

Tibia · Post by **Tibia** » Mon Oct 20, 2008 8:34 am

Just a suggestion to save you some sanding later....

Wet your hands, and smooth out the clay now, before it cures. Don't bother going for perfection, especially since it is on the inside of the case. But the smoother it is now, the less sanding you need to do to make it smooth. I know this is the side that'll be inside, but if the plastic is soft enough, it will dip into imperfections.

bacteria · Post by **bacteria** » Mon Oct 20, 2008 8:46 am

Indeed, tomorrow I will give it a good sanding. It is fairly smooth at the moment, although not quite level everywhere, which will be cured with the sanding process. Once sanded, I will coat it in varnish to protect the surface. I don't have any silicone to coat the mold with, hopefully gravity and the fact the mold is varnished will help. I may put a light covering of washing up liquid over the mold just before applying the plastic sheet, to hopefully assist the mold coming free easily.

bacteria · Post by **bacteria** » Tue Oct 21, 2008 5:54 am

Ok, mold dried ok but I did get a couple of large cracks. Added more clay to seal. Did major sand, filled in remaining small gaps, left to dry again (in airing cupboard for a couple of hours - nearly done now).

Completed the vacuum table. Final dimensions (approx): 23cm x 33cm x 12.5cms.

Added a 16mm strut (the wood I bought earlier) around the inside edges of the top and bottom sections, used some No More Nails glue, and then nailed the sides to top and bottom for strength. To ensure the unit is airtight, next job was to stick some thick paper tape around the edges and seal down.

Last job was to cut thin strips of foam and glue to the sides, this ensures an airtight seal when the frame with the plastic is applied.

Plugged it into my Dyson, works fine. Quite decent suction. If I need more suction, I can get an extra plumbing addon which will enable two vacuum cleaners to work at the same time!

I then put some plastic right angled strips on the sides so I have a guide when lowering the frame onto the table.

Pic with frames and plastic sheet in place - the plastic will be secured between the frames by screws.

Anyway, table works. Need to finish off the mold now...

bacteria · Post by **bacteria** » Tue Oct 21, 2008 7:28 am

Ok, mold finished.

Got oven to 220 Celsius, put in first sheet of plastic. Thought the plastic was starting to give, after 7 mins, opened oven, it had covered the internal capacity of the foil container! I was left with a wasted sheet. Second sheet, more careful, after 3 - 4 mins the plastic had dropped enough, turned on vacuum, removed plastic from oven, closed oven door, put plastic over mold.

The suction was so good that it sucked the plastic down instantly and then kept on sucking. It sucked out the plastic container piece from the mold (hence the dip in the pic, it was supposed to be flat in the middle!); and broke the mold. I thought the clay was hard enough, obviously not. Proves the vacuum table works properly though. I will have to turn on the vacuum machine once the plastic is over the mold in future I think though.

The clay was quite expensive, I have two choices remaining for making a mold now; think I will just use some pine blocks and have a go at carving, if I can't do that properly, I will have to buy some more clay, 3 packs @ Â£9, make the mold and let it set for a few days; looks like it needs it.

As you see in the pic, the plastic buckled on the sides in a couple of places (eg bottom left), is that usual, and how can I avoid it?

The other good bit of news from this disaster, is that I thought the plastic had a bit of give to it and I wanted it rigid, if you remember? Well, after the heat treatment and cooling, the plastic becomes very rigid indeed. Nice!

I just need to get a working mold now!

So...

GOOD NEWS - Table works. Concept works. Vacuum cleaner works and is powerful enough for job. Got a mold, all be it not great; however half of the sides look really nice (rest suck).

BAD NEWS - Wasted two of my eight sheets of plastic. Mold broke and I need to make a new, better one. Wasted money on the clay by trying to save money.

HBN · Post by **HBN** » Tue Oct 21, 2008 8:18 am

My gods... It worked TO good, you could say.

Good job of the table. Try plaster for the mold next time. And Don't make it hollow (For some reason it took until now for it to register that's what you did...sorry). That'll kill any strength it has.

bacteria · Post by **bacteria** » Tue Oct 21, 2008 8:55 am

HBN wrote:My gods... It worked TO good, you could say.

Good job of the table. Try plaster for the mold next time. And Don't make it hollow (For some reason it took until now for it to register that's what you did...sorry). That'll kill any strength it has.

Thanks, I was pleased the table works, as you say, if anything, too well!

Tried wood just now, it will take forever as I don't have the right tools to do it with any speed.

Don't want to craft a mold for plaster, it will be hard to shape it once set. I want to make a curved casing rather than being too straight. I think I will just have to buy some more clay and get on with it. At least with clay you can make the mold as you want it to be and then just sand it afterwards to the finished shape. I got some nice curves on the sides (solid bits). If I hadn't penny-pinched I would have finished the mold by now!

Oh well, not bad for first effort!!

I am hoping, if I manage to succeed in making successful cases, to offer them for sale for anyone wanting to make a PlayStation 1 or N64 portable; or anything else that fits - anyway, let's get mine working first...

collinE · Post by **collinE** » Tue Oct 21, 2008 10:33 am

If you wanted to do clay again, you could use a block of wood instead of a plastic lid and keep it in?

I got some plastic bunching on mine and it was because the plastic had sagged too much before I pulled it out. don't know if that's your problem.

Sorry to hear about all that. After the first couple tries I was worried I wouldn't be doing vac-forming for a case, but it's rewarding when its done. that's for sure.

bacteria · Post by **bacteria** » Tue Oct 21, 2008 2:03 pm

collinE wrote:If you wanted to do clay again, you could use a block of wood instead of a plastic lid and keep it in?

I got some plastic bunching on mine and it was because the plastic had sagged too much before I pulled it out. don't know if that's your problem.

Sorry to hear about all that. After the first couple tries I was worried I wouldn't be doing vac-forming for a case, but it's rewarding when its done. that's for sure.

CollinE - Agreed, wood would have been more sensible! Wish I had done that before. May well use a block of MDF this time around.

The couple of places I got some plastic bunching may well be due to what you suggested. It is trial and error getting it right!

Takes a lot of effort to make the mold and table; however I did get a good idea of what I would end up with.

Bought another eight sheets of the plastic today, via e-bay.

My next mold will be far better and smoother!!

BTW - It cost about Â£12 to make the table unit (about $22), which is cheap. The expense is in the clay and plastic sheets! Making a mold (ignoring my first flop) will cost about Â£9 per half shell and the plastic costs about Â£1.75 per sheet (inc delivery); of course you need to expect to waste some sheets to get a good one cast!

khaag · Post by **khaag** » Tue Oct 21, 2008 8:19 pm

Also, try placing the plastic over the mold before turning the vacuum on; it might yield better results.

bacteria · Post by **bacteria** » Tue Oct 21, 2008 10:08 pm

Indeed, doing it before the frame was in place made the plastic sheet distort before I could get it in position, so next time I will get the frame in place and then turn on the vacuum.

Rather than messing about with a footswitch, or whatever, I will make a handle on the frame so I can press the frame downwards with one hand and not two, leaving the other hand free to turn the vacuum on!

bacteria · Post by **bacteria** » Wed Oct 22, 2008 10:03 am

Ok, today bought the following: 4 packs clay, plastic primer spraypaint, black metallic spraypaint, metallic spraypaint sealer, clay shaping tools. I also have 14 remaining plastic sheets, plastic weld glue and also two packs of bondo. Think I am pretty set!!

I had thought about making the cases white, but thought that looks very nice but a bit "plasticky" so decided on metallic instead of plain, and black as that looks cool. Spent over Â£15 on the three spray cans, so hoping it was a wise investment!!

Plan on selling some of my cases if I am successful with mine, to help others making portables (and to help repay my outlay!).

bacteria · Post by **bacteria** » Fri Oct 24, 2008 5:11 pm

Cut outline of case out of paper, folded in half to ensure system is symmetrical. Cut out shape out of mounting board.

Cut a piece of 18mm MDF out and used a staple gun to secure the mounting board to the MDF. This isn't going to give! The MDF bulks the mold out so I don't use excessive amounts of clay.

Completed the top and one of the sides in about 20 mins; nice and flat on top and shaped on side, thanks to the tools I bought (pic above).

Post by **marshallh** » Fri Oct 24, 2008 9:49 pm

Good start. Here are a few tips to get you better results:

1. On your former itself, the holes you drilled around the perimeter - I tried that method at first. I had much better luck with drilling a grid of holes about 3/4" spaced from each other. It's more work, but gives better airflow and sucked the mold down better. It would probably help get rid of the fold in the plastic you have.

2. Stay away from modeling clay. Besides being expensive for the amounts you need, it's impossible to get it smooth. Better to start with something that already has a rigid shape. Your idea of pine blocks is a great step. MDF works too but pine is easier to cut. I'd get some half inch or 3/4 inch sheets and cut out your design with a coping saw. If you build using layers you can get some cool effects.

3. Lay out your design onto graph paper. You want it as symmetrical as possible, it's easy to pick out inconsistencies with the eyes.

4. You might know this already, but putting draft onto your mold will really help when it comes time to take it off your plastic. Basically, the edges of the mold are not perfectly vertical, but it's wider at the bottom and slopes inward.