Vacuum.Forming.Table


It's a minor project because it's so simple! You can have one working in no time, too! 

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This How-To is also available at http://benheck.com/phpBB/viewtopic.php?t=18142

 

 Well I figured that with the absolute success of my own vacuum table, I would write a "how-to" for making your own table like mine: Click to enlarge

It's dirty, looks like dirt, but works absolutely amazingly.

This is largely based off the "Studio Creations" table (see Turbo's Sticky), and is probably redundant, but I'm going to write this anyways. It's also very lengthy.

To make a table properly, I find it's best to fully understand what you are trying to accomplish in the end, and build it following rough instructions from there. If that's not how you roll, this isn't for you.

Vacuum forming uses a vacuum cleaner or shop-vac to create an airtight seal around a positive. The low pressure causes the melted plastic to form exactly to the positive. Pretty simple, right? It is! What do we need to do to accomplish this?

A shop-vac must be sealed airtight to a table, which must be sealed to the plastic. Now, melted plastic isn't very stable, so it must be held by a frame.

Click to enlarge

Parts List:

To Make the entire machine, you will need the following parts:

- 8 L-brackets.
- 32 1/2" screws for the L-brackets
- Wood Glue, or other fire-proof airtight sealant for your frame.
- 1"x 3" wood of a length determined by the size of your oven. Continue reading to determine your length needed.
- 1 sheet of 1/4" plywood, although any airtight surface will work. Size is determined later.
- Shop-vac
- Plastic (preferably styrene)

The list again, less commentary.

- 8 L-brackets
- 32 1/2 screws
- Wood Glue
- 1" x 3" wood
- 1/4" plywood

-Shop-vac
- Plastic

As I don't know the proper name for the L-brackets, here is a picture, along with the screws I used to hold the bracket in place:

Click to enlarge

First is the positive of the shape your plastic will take. This is very straight-forward, and the stickies over at Benheck.com have various methods of performing this task. I used wood. If you have a little patience (and a little clay to touch it up) it is possible to make a wonderful piece of plastic from a wooden mold.

Second is the plastic sheet. I used styrene, although several other plastics such as Acrylic supposedly work great too. The thickness will ultimately be determined by the application. For a portable, don't go lower than .060", or 1.5mm. I bought a big sheet of this, so it is what I will use. .080" (2mm) is probably optimal for a portable, or most other applications. But if you need something a little less stiff, go with .060".
 

Third is your heating source. For cheap people, this means your oven. Measure it's size. Length and width. Write that size down, and keep it in mind.

[b]Fourth[/b] is [u]the table[/u].

Click to enlarge 

Look how simple it is!


This does not need to be complicated at all. I used a roughly-cut piece of plywood, about 5 inches bigger that your oven in both directions (for an easy fit), so that the frame will fit nicely over it. A hole needs to be cut in the middle for the vacuum's hose. Luckily enough, I had an old hand-powered drill with an attachment exactly for this. It may be slightly harder for you to make this hole, but try to make it as round as possible, and as tight a fit to your hole as possible. Try a jigsaw-cut hole from a drilled starting hole. When you want to use the vacuum as a vac-table, simply use some hot-glue to seal the gaps between the hose and the table, and rip the hose off when you don't want to.

Next is some weather stripping. A nice squishy foam kind is best, because it will suck the frame down creating a near-perfect seal. Make sure it's the airtight kind, of course. Lay this down under where the frame will go.

Click to enlarge 

Note the L-bracket's placement. It should be inside or outside of the weather stripping, to minimize air leakage.

Obviously, this table needs to be put on top of something, such as a table with a hole in it (if you have one like I did ), between two cinder blocks, or anything else that will let your vacuum hose hang nicely. Be creative, it's not that hard to figure something out.
Click to enlarge 

The set-up, minus the frame. Notice how the "hose" is allowed to fit underneath the table (It's actually just part of the hose). For someone less fortunate than me, this will be in between two cinder blocks or other item of the supporting kind.
 

Fifth is the frame.
Click to enlarge
Click to enlarge
Note the placement of the screws. From the bottom of the bottom frame UP, so the ends don't interfere with the seal. Also note the bits of wood I added to make the frame fit nicely in the oven.

The most important part. This requires some precision, in order that it fits nicely over the oven rack holder things. Remember those measurements from your oven? Multiply both numbers by two, multiply that number by two, and get that amount of 1" x 3" wood. Softer wood is worse, as it will ruin faster, but I used pine and it looks like it will last for a few more times. The first time I placed the frame in the oven it did not fit. I simply cut it down to size. No big deal at all. Then it was too small, so I put a small lip on the edges made of some scrap wood. Don't worry if you mess the frame up the first time, it can be fied easily enough.

You will also need some screws that are 1/2" long (or whatever doesn't go through the frame's wood). You will need some flat "L" brackets as well, to hold the frame together.

Piece the precision-cut wood frame pieces (4 lengths of each oven measurement) together, in a top-frame and bottom-frame arrangement.

The L-brackets will go on the bottom of the bottom frame and top of the top frame. Then, from the bottom frame, drill 4 holes for screws that will ultimately clamp the two frames together, holding the melted floppy plastic inside. With all the screws in the frame, screwed in tightly to minimize the gap, pour wood glue in the spaces between wood sections.

Preparation:

Cut the plastic to size to fit the frames. Use masking tape to tape it to the bottom frame, just in case your seal isn't quite good enough between frames. Use the 4 screws to clamp everything together. Put it in the oven until it sags around 1.5-2 inches. You will know when to take it out, because it starts to sag noticeably faster. Around 2.5-3.5 inches, take it out. As soon as possible, put the frame over the table, lined up with the weather stripping. Put it down directly DOWN. Otherwise, it will stretch. KEEP THE VACUUM ON until the plastic completely cools. For me it was a matter of seconds, but I did it outside on a cold day in the midst of a Canadian winter. You may need to wait longer.


Parting Notes:

- Make sure there is good airflow between the vacuum hose and the mold. Sometimes the mold will cover the hole and prevent vacuum sealing.

- When turning the vacuum off, the plastic doesn't need to be cold. It just needs to be hard, not still soft. Warm to the touch is fine as long as it's hard to the touch.

- This table design folds up amazingly small for storage. Look!

Click to enlarge