www.TK560.com Forum Index www.TK560.com
Vacuum Forming, Movie Prop, Sci-fi and GIjOE Forum
 
Log in to check your private messagesLog in to check your private messages

Log inLog in  RegisterRegister


Profile  Search  Memberlist  FAQ  Usergroups
draft of ch. 2 (make a former) of possible book-like thing

 
Post new topic   Reply to topic    www.TK560.com Forum Index -> Vacuum Forming & General Stuff
View previous topic :: View next topic  
Author Message
drcrash
Guru


Joined: 04 Sep 2006
Posts: 705
Location: Austin, Texas

PostPosted: Mon Dec 18, 2006 1:09 pm    Post subject: draft of ch. 2 (make a former) of possible book-like thing Reply with quote

EDIT 7/4/07:

This stuff is mostly obsolete... for most people's purposes, it's better to read my "Instructable" titled Make a Good, Cheap, Upgradeable Vacuum Former: http://www.instructables.com/id/E8RW98YF3C4XLCQ/

Aside from the stuff that's done better (with pictures) in the Instructable, there's not much here, except for a discussion of various ways to make frames. If you want to make wooden frames, or more rigid aluminum frames, skip forward to that part.





VACUUM FORMING FOR ARTISTS, CRAFTSPEOPLE, AND WANNABES

[This is part of a projected book-like thing I may or may not finish writing... I thought this chapter might be useful in itself, so here it is. Most of the more advanced content for the rest of the "book" is out on the web already, in some form or another, in scattered postings by "drcrash" on user forums at www.hobbymolding.com, www.tk560.com, cnczone.com www.rcgroups.com, and www.rcuniverse.com. -- Dr. Crash ]

---

Chapter 2 (Version 0.1 *DRAFT*)

MAKING A SIMPLE BUT FLEXIBLE VACUUM FORMER

In this chapter, I'll tell you how to make a simple vacuum former for common thin plastics used by hobbyists.

This should take one trip to a hardware store and maybe a stop at an office supply store, and an hour or so with basic tools. If you don't have a good vacuum cleaner lying around, you might want to stop by a couple of thrift stores, too. (More on that in a bit.) If you're a serious recycling-oriented cheapskate like me, you may spend several hours scrounging around at thrift stores and the like. Or you could pay a few extra bucks here and there.

Total cost to build the basic vacuum former shouldn't be over $40, and is likely to be substantially less; it may be almost free if you have random materials lying around and work with what you've got. (I give several alternatives for each major piece to help you do that.)

A vacuum former consists of a few basic things:

1. A heater to heat a sheet of plastic until it's soft and rubbery. We'll use regular kitchen oven for that. A toaster oven will do if you only need to make small parts.

2. Something to hold the plastic while it's being heated, moved to the forming surface, and draped over the mold. We'll make a pair of frames out of aluminum (or wood), and clamp the plastic between them using manuscript binder clips (or bolts).

3. A forming surface called a platen, to hold a mold; in our case the platen will be a board with a hole in it

4. A vacuum source to suck the rubbery plastic onto the mold, and hold it there until it cools. We'll use a vacuum cleaner for that.

5. A means of moving the plastic to the heating source, and from there to the forming surface to be formed. For the kinds of things we'll be doing---making objects no more than a foot or two across---we can just use our hands, covered with leather gloves.

The "platen" and "table" for our little former are just a board with a hole in it and some weatherstripping around the edge, and a couple of appropriately-sized things to prop it up on. If you want to get fancy, you can build or buy a box to hold it up. You'll want to set this board up near your oven, so that you can pull the plastic out of the oven, position it over the platen, and bring it down over the mold quickly---within a couple of seconds or so. Thin plastic cools very quickly, so wasted motion is bad.

For flexibility, a good size for the platen/tabletop is the inside size of your oven, or maybe an inch bigger all around. You don't have to use all the area, and usually won't if you're making small things, but if you want to take full advantage of your oven sometimes, you'll want a tabletop that big.

Given a tabletop that big, you can use it as several different-sized forming platens---almost that size, a little smaller, or a lot smaller. Instead of putting one gasket around the edge, you can have several removable gaskets of different sizes, attached to sheets of something thin and a little flexible. (Thin plastic from a dumpster, or even posterboard.) You can pick the size you want to use, put it on the tabletop, and seal it around the edges with tape.

(That's why you want your tabletop a little bigger than the largest sheet of plastic you'll form. You need room around the gasket for about a half-inch of whatever thin stuff the gasket is attached to, plus about another half inch of tabletop to tape it that to. You also want a quarter inch or so extra for an oversized gasket that gives you slack about exactly where to bring the plastic down... so give it about 2 1/2 or 3 inches in each direction.)

If you don't expect to make things that big, you may want to go a bit smaller, say 14 x 20 inches; that's be big enough to mount a gasket for plastic up to 12 x 18 inches.

To keep things simple at the outset, you may just want to put one gasket directly on the table. You can remove it when you want to upgrade to a multiple-sized system, and make several reusable removable gaskets on their own sheets. (You'll destroy the first gasket taking it off, but that will only cost a couple of dollars.)

You may have seen vacuum formers with a platen with lots of tiny holes in a big grid; lots of high-end vacuum formers have that, so you might assume it's better than one big hole in the middle, but usually it's not. If you're only making one object at a time, rather than putting a bunch of small molds on a big platen, there is usually no advantage at all to the fancier platen.
For our purposes, there's actually a disadvantage. The one-big-hole system is a bit easier to adapt to different sizes and shapes of plastic. You just put a different-sized gasket around the hole, and it works. (And as I'll describe in another chapter, there are other ways to spread the vacuum around multiple molds, without actually modifying the platen.)

Until you find an actual need for a fancier platen, don't bother making one; your time is likely better spent getting experience with vacuum forming, and making enhancements that would benefit you more.

Cutting the Board to Size

If you're the handy kind of person with tools and wood lying around, you probably have something you can use, and know how to do it. You just want something flat and sturdy, like 1/2" MDF or plywood, preferably smooth on one or both sides. (If it's not smooth, sand it a little on one side.)

If you don't have that kind of stuff lying around, go to the hardware store and get a piece of 1/2" MDF ("Medium Density Fiberboard".) It's cheap, very flat, smoother than wood, and pretty sturdy. (It's like particle board, but finer-grained, denser, and stronger.) You can probably buy a piece that's 2 ft. by 2 ft. for a few dollars; you might have to buy a 2 x 4 piece for a couple of dollars more.

If you don't have a power saw, or are lazy like me, have the people at the hardware store cut it to size for you. At places like Lowe's or Home Depot, they'll usually do the first cut or two for free, and charge you 50 cents or so for more cuts, so this is free or very cheap, and they sweep up the sawdust. (They don't do "precision cuts," but for this, you don't need much precision.) You get to keep the pieces they cut off.

OK, now you have a board with a hole in it. Good going.


FINDING A GOOD CHEAP VACUUM CLEANER

If you have a good canister vacuum cleaner sitting around, it's probably fine for vacuum forming thin plastic. An upright may be fine, too, but many of them leak when you switch to using the hose.

Many people think that you need a big (wet/dry) shop vacuum for vacuum forming, but many home vacuum cleaners are just as powerful. (And some shop vacs these days are pretty lame.) Buying a shop vac just for vacuum forming is a bad idea, because most powerful shop vacs are big and bulky; they suck the air through a big bucket that is just slightly worse than useless for our purposes.)

If you don't have a good vacuum cleaner, you don't need to go out and buy an expensive one; if you don't know if your vacuum cleaner is a good one, bear with me---I'll tell you how to test it.

You can probably get a perfectly good vacuum cleaner for a few dollars at a thrift store. It probably won't have all the attachments, but you don't need them. If it's missing its filters or bag, that's okay too, as long as it sucks. I've gotten several powerful vacuum cleaners at a Goodwill Blue Hanger store for $2.50 to $5.00 each.

(Blue Hanger stores are where they take stuff that doesn't sell quickly at regular Goodwill stores. If it doesn't sell pretty quickly there, it's scrapped or dumped. Blue Hanger stores are a great place for tinkerers to forage for useful stuff cheap. The stock turns over every few days, so if there's one near you, you might stop by regularly.)

Take a piece of craft foam a few inches across with you to the thrift store; you can use it to test how hard a vacuum actually sucks, by putting it over the end of the hose and seeing how far the foam is sucked into the mouth of the house. (If you don't have craft foam lying around, try to find a piece of some kind of sheet rubber or thin "closed-cell" foam---the kind you can't blow through, because the holes in the foam don't connect up to make paths all the way through.)

When looking for a vacuum cleaner, your first cut should be the wattage or amp rating. That's usually on a label somewhere on the machine, often a small one stuck on or molded into the housing near where the power cord connects. The higher amp rating, the better. 8 amps is pretty good, and 10 to 12 amps is great. If the label doesn't give the amp rating, it probably gives the watts. Over 1000 watts is good. 1200 or more is even better. (Watts and amps are equivalent at a given voltage, such as regular 110 Volt AC wall outlet electricity. The wattage is simply the amperage times the voltage; 10 amps comes out to 1100 watts at 110 volts.)

Don't rule out smaller, somewhat lower-rated vacuums, especially some of the little 8-amp canister vacuums or even 6 to 8 amp hand vacuums. They may not suck as much air against low resistance as the bigger vacuums, but they may suck just as hard, once they've sucked plastic down, and that's what really counts for a small vacuum former.

Once you've narrowed the field to powerful vacuum cleaners, their performance will still vary depending on whether they're well-designed and working right, and whether they're designed to to pull a lot of air against little resistance, or pull a lower volume of air harder. There are no good specs for that, so it's good to test each candidate with the craft foam test.

To be rigorous, you may want to actually measure how far the foam is sucked in, and write it down. (Stick the end of a pen or a toothpick or something into the mouth of the hose until it meets the foam, and pinch it even with the mouth of the hose. Measure that with a ruler, or just make a mark that length on a piece of paper.)

When you do this, notice that some vacuum cleaner hoses are different diameters than others. The foam will pull further into a larger-diameter hose, at a given level of vacuum. So note the diameter of the hose, too, and use the ratio between the diameter and the sucked-in depth. Eyeballing it is probably fine if you are doing side-by-side tests, or if just draw the curve on a piece of paper after marking down the diameter and the depth.

(This may not be good enough if you're considering shop vacuums with large-diameter hoses. In that case, you may want to buy an adapter at the hardware store, which stops a 2 1/2" hose down to 1 1/4", or jury rig a stopper with a hole in it, a little smaller than the inside size of a normal vacuum hose. Anything flat and reasonably rigid, three inches or so across, will do. Foamcore board is strong and rigid enough, and easy to cut, so if you have some lying around, use that. Cut a 7/8" diameter hole in it, and glue a similarly-shaped gasket of craft foam to one side. Glue a piece of craft foam over the hole on the other side. (Or just tape it, sealing it around the edges with tape.)

Now you have a vacuum gauge of sorts, which works with all sizes of hoses---just press the end of the vacuum's hose around the hole on the gasket side, and see how far the foam on the other side sucks in.

Attaching the Vacuum

Now that you've figured out what vacuum cleaner you'll be using, you need to figure out how to attach its hose to a hole in a board.

This is the most tedious and annoying part of making a simple vacuum former, because vacuum cleaner hoses are not designed to exactly fit plumbing pipes, or anything else---and different brands of vacuum cleaners use slightly different diameter hoses.

The good news is that almost anything will do. If you've bought a cheap vacuum cleaner just for this purpose, you can cut a barely-big-enough hole in the board and just glue the vacuum cleaner hose directly into it. Or if you have an extra attachment such as crevice tool that fits your hose, and you're willing to sacrifice it, you can cut that down and glue it into the hole. This has the advantage that you can detach the hose from the board, making it less awkward to store.

I use a 1 1/4" galvanized steel "floor flange" plumbing fitting. (Which costs about $4 to $6 depending on which hardware store you get it on.) That provides a standardized interface of sorts, so that I can attach different vacuum cleaners to different vacuum formers, and it's big enough for vacuum formers up to about 2 x 4 feet. Unfortunately, each hose requires adapting to fit that. The adapter can be made from a 1 1/4 PVC plastic pipe "nipple" (a very short bit of pipe threaded on both ends, plus whatever it takes to adapt your hose to your nipple. (Please, no nipple-sucking jokes.)

A lot of people use a 3/4" galvanized pipe flange, which is big enough for vacuum tables up to about 2 feet square.

If you are using a shop vac with a big hose, 3/4" pipe is a very convenient size. You can get an adapter for about $4 designed to let you use small-shop-vac-hose-size (1 1/4") attachments with a large-hose-size hose. (They have them at Lowes and Home Depot.) That adapter fits pretty well around (not inside) a 3/4" pipe nipple, so you can screw the nipple into the flange, slip-fit the adapter over the nipple, put some duct tape around it, and you're good to go. (Test-fit the nipple and adapter in the hardware store before you buy... the inside size of the adapter may not be standardized.) Or you could just glue a nipple into a hole in the board, so that you save 4 to 6 dollars on the flange.

Another easy way of plugging in a 2 1/2" shop vac hose is to get a "multi-tool" adapter intended for plugging the shop vac into different dust collection systems for different tools. This is a black somewhat rubbery plastic thing that fits over the vac hose, with a square mounting flange and a stepped series of narrowing diameters, like this:

Code:

                      +-+
                      | | <- square mounting flange
          +-----------| |       w/bolt holes
          |           | |-------+
          |           | |       |-------+
2 1/2"    |           | |       |       |-------+
 hose     |           | |       |       |       |
 fits ->  |           | |       |       |       |
 here     |           | |       |       |       |
          |           | |       |       |-------+
          |           | |       |-------+
          |           | |-------+   stepped
          +-----------| |           adapters
                      | |
                      +-+


All you want is the flange, so just cut it a half inch past the mounting flange, getting rid of the narrower adapter segments and all but a half-inch of the first one:
Code:

                      +-+
                      | | <- square mounting flange
          +-----------| |       w/bolt holes
          |           | |----+
          |           | |    |
2 1/2"    |           | |    |
 hose     |           | |    | keep 1/2 of first adapter,
 fits ->  |           | |    | cut hole in board for it,
 here     |           | |    |
          |           | |    |
          |           | |    |
          |           | |----+
          +-----------| |         
                      | |
                      +-+


(Keep a half inch of the first one to help keep the rubbery plastic reasonably rigid.) You'll want to cut a hole in your board to accommodate that 1/2" part, and drill four bolt holes.

If your hose doesn't happen to fit exactly into or around your flange or nipple, a serviceable interface between the nipple and hose can usually be slapped together with some craft foam and some duct tape. It won't be sturdy, and you'll probably want to do something better later, but it will work and get you going. Once you decide you're happy with your configuration, you can cut up an attachment, or find just the right scrap of pipe or tubing to shim things... but for now, don't bother. Just wrap some craft foam around the smaller tube until it fits into the other tube, work it in, and put duct tape around the whole thing. (If one won't fit inside the other, butt them together and duct tape around the joint. Then maybe put some splints around it, to make it a little more sturdy, and duct tape the whole mess.)

Duct tape works surprisingly well for sealing vacuum systems, if you apply it carefully, with no wrinkles at the crucial joint. Vacuum tends to suck things in, rather than blowing them apart, so duct tape around the outside is your friend. It's probably overkill, because if you're using a vacuum cleaner, small leaks don't matter much. (Vacuum cleaners can suck a lot of air fast, so they can stay ahead of small leaks without their affecting the level of vacuum much at all.)

Another cheap and easy option is to cut the hole to fit the hose, slip-fit it, and use silicone caulk around the outside. Silicone caulk is a great sealant, but not very good glue. If you seal the board with paint where you're going to glue it, you can scrape the stuff off later, if and when you decide to re-do the joint. (If you don't seal the board, you can scrape most of it off, and cover it with a flange later. No big deal.)

So, once you've figured out how you want to connect the hose, cut the appropriate-sized hole in the board.

A drill and a hole saw the right size is handy for that, but a drill and a portable jigsaw will do. If you're using a flange, the exact shape of the hole doesn't matter---it can be very ragged, so you can make do with a drill, or even a chisel. Use whatever you've got or can borrow than can make a hole.)


PICKING THE PLASTIC SHEET SIZE(S)

Now you need to decide what size of plastic you'll start with, if you haven't already, and whether you're likely to want more than one size.

If you only want to make one kind of things, or a few kinds of things in a narrow range of sizes and shapes, you'll want to pick a size that's big enough for whatever you're making, plus a bit. More likely, you can identify a couple of sizes that will do fine for most things you do, and one size that's fine to start with.

So, for example, if you're making rocket nosecones and fins, or small model plane pieces, like cowlings and/or or bubble canopies, you probably only need plastic that's 8 x 10, or even smaller. A lot of people use 5 x 5, or 10 x 10, or 12 x 12 squares.

I don't like squares. Most things aren't square, or circular, so you can do more things if your plastic is longer one way than the other. All other things being equal, one side should be significantly longer than the other, so that you can choose an orientation to fit things in without wasting a lot of plastic. It shouldn't be long and skinny, though, unless you'll be mostly making long and skinny things. (If you make model plane fuselages and wings, that may be a consideration.)

An "aspect ratio" of 2:3 or 3:4 is pretty good, all other things being equal---say, 8" x 12", or 12" x 16".

Another consideration in picking plastic sizes (and aspect ratios) is where you'll be getting your plastic. If you buy little 8 x 10 sheets from a hobby or craft store, you'll pay through the nose. If you do a moderate to large amount of vacuum forming, you'll want to buy larger sheets of plastic and cut them into smaller pieces. Large sheets of plastic usually come in dimensions that are 2 feet or multiples of 2 feet. The largest and most economical common sheets are 4 x 8 feet.

(Here in the backwards, metric-impaired US, that is. If you're in a more metrically advanced country, you'll have to figure out common plastic sheet sizes there.)

All other things being equal, it's nice to be able to divide a 2 x 4, 4 x 4, or 4 x 8 sheet evenly in two or three pieces one way, and two or three or four pieces the other way.

Some nice sizes for that are 8" x 12", 12" x 16," 16" x 24". For example, you can take a 2 x 4 foot sheet of ceiling panel fluorescent light diffuser from the hardware store, and cut it into 3 pieces that are 16 x 24, 6 that are 12 x 16, or 12 that are 8 x 12.

Unfortunately, some plastics are sold in different dimensions. For example, craft foam is fun stuff to vacuum form, if you want to make rubbery foam things. It generally comes in 9 x 12 or 12 x 18 sizes, or metric sizes that are a bit off from those in both dimensions. (A little longer one way and shorter the other.) You can of course use a 9 x 12 piece as an 8 x 12 piece (or a 12 x 18 as a 12 x 16), and waste an inch or two; so unless you think you're likely to make things that fit into 9 inches but not 8, (or 18 but not 16), you'll probably be fine. If you turn out to be wrong on that, it's not hard to make a new frame and a new gasket for another size you decide on later.

So think a little bit about what you'll be making and where you'll get the plastic, but don't worry about it much. Pick a seemingly-good size for what you think you'll likely be doing, and go with it. You can change it later, or bite the bullet and build adjustable frames.

In picking a size, leave a couple of extra inches on either side, beyond the dimensions of what you want to make. The clamping frame that holds the plastic will cost you about an inch of usable area around the perimeter, and sometimes it's nice to have a little spare plastic around the edges. (It may help in forming "difficult" shapes, for reasons I'll explain later.)

MAKING THE FRAMES

This section might be called "way too many ways to make frames and clamp them together." I'm giving several choices; all of them work pretty well, and none of them has been shown to perform better or worse than the others. (Nobody's done controlled experiments, so far as I know.) Sorry about that.

If you don't want this much detail, just skim along until you see a method that appeals to you, pick that, and do it. Skip the rest.

Your little vacuum former will use a pair of frames around the edge of the plastic, clamped together on either size, squeezing it tightly so that it can't slip out while you're stretching the plastic over the mold.

There are a couple of common basic ways of doing this. (And several variants). One is to make the frames out of wood---yes, wood---with bolts that clamp the frames tightly together. The the other is to make them out of fairly thin extruded aluminum, either angle metal or window screen framing material, and clamp them together with manuscript-type binder clips. (The cheap black ones with silver bent-wire handles work great.)

Making Frames Grip Better

Whichever way you make your frames, if you're going to be forming thick plastic---1/8" or more---it's good to make your frames grip better by putting something rough on the bottom side of the top frame, where it grips the plastic. Some people do this with adhesive-backed sandpaper or similar gripping-surface material.

For metal frames, a better way to do that is with J B Weld (or a similar high-temperature epoxy) and some sand. (J B Weld seems to be available in all hardware stores.) Mix up a little epoxy, and smear it smoothly around where the upper frame will meet the plastic. Then sprinkle sand on it, and pat the sand into the epoxy. Let it set, and then rub the excess sand off. This will give you a sandpaper-like gripping surface that won't get messed up by the heat of an oven.

You can use epoxy and sand for wooden frames, too; any epoxy should do---epoxies are generally fairly heat-tolerant, and the wooden frames themselves will partially insulate the inner surfaces and the glue. Self-adhesive grippy stuff will probably work fine for the same reason. (Or work for much longer than with aluminum frames, anyway.)

(Don't do this to the bottom frame; the bottom frame should be smooth on both sides, to make a seal with the plastic on one side and the gasket on the other.)

WOODEN FRAMES

You might think that wooden frames would catch fire in an oven, but for most plastics you only need a forming temperature of 250 to 350 degrees, and wood doesn't burn until it reaches around 450 degrees. The oven may be a bit hotter than the plastic-forming temperature, to get the plastic to that temperature within a few minutes, but the frames and plastic are only there for a few minutes.

If you use very cheap wood like cheap pine or "white wood," it will eventually char after many bakings. Hardwoods last longer, essentially forever for hobbyist purposes, but they cost a bit more. You can also use plywood, preferably good hardwood plywood about 3/8" for frames up to about 9 x 12, or 1/2" thick for larger frames.

Which you choose is up to you, and you may want to choose depending on the tools you have available, and the materials you have lying around.

PLYWOOD FRAMES

If you have a portable jigsaw, it's easy to make frames out of plywood. You can just cut them out, and the leftover pieces from the middles can be used to make a smaller set of frames later, if you want. The inner dimensions of the frame should be about an inch to an inch or an inch and a quarter smaller than the plastic sheets you use. This will give the frames about a half-inch of plastic to grip. The frame sides should be about two inches wide, or an inch and a half bigger in both directions than your plastic sheets.

(To make the cutout, drill holes in the corners, a bit inside the desired corner to account for the radius of the drill bit, and connect them with jigsaw cuts.)

To clamp the frames together, use regular (coarse-threaded) 1/4" bolts and wingnuts. The bolts should be long enough to stick up about a half inch when the heads are countersunk (see below) and the frames are clamped together with nothing in between them. This will let you clamp plastic about 1/4" thick, with enough bolt sticking out to screw the wingnut onto.

Drill 1/4" bolt holes through both frames of the pair, far enough from the inner edge that they will clear the plastic with a little room to spare. (In case your plastic is a little bit oversized.) These holes should be spaced about 4 inches apart, and maybe a little closer near the middle of each edge. (If plastic pulls out of a frame, it generally does so near the middles of the sides; you need a little bit better clamping there.) For an 8 x 12 frame, two bolts on each long side and one in the middle of each short side is good. For a 12 x 16 frame, three on the long sides and two on the short sides is good.

(Whichever frame of a pair is smoother, use that for the bottom frame; it will have to make a seal with the weatherstrip gasket, and another seal with the plastic. If it's not very smooth, sand it pretty smooth where it will clamp the plastic and where it will rest on the gasket. Grab a marker and mark the frames---which is the top frame, and which side goes up, and which end is which; likewise for the bottom frame.)

Countersink bolts into the bolt holes, so that their heads don't stick up, or not much. (Down, when in use.) You don't want them to interfere with the gasket. The bolt holes should be outside the footprint of the gasket, so it's not critical that the frame bottom be very flat there, but if you don't hit the gasket dead center, you don't want a big bolt head distorting the gasket a lot and creating a leak. Glue the bolts into the bottom frame, using the top frame for alignment; make sure the top frame fits onto the bolts before the glue sets and its too late. Epoxy glue is good for this. (If the bolts bind a little bit, after the glue has set, you can enlarge the holes in the top frame---probably just by working it up and down on the bolts a few times, so that the bolt threads scrape away a little wood.)

(BTW, if you don't know what countersinking is, it means enlarging the bolt hole where the head of the bolt goes, so that the head goes into the hole instead of sticking up. If you don't have a countersinking bit, you can do by hand it with a knife.)

WOOD STRIP FRAMES

Some people make wooden frames out of 1 x 3's or other similar wood. These are easy to make with just a handsaw and a drill, or you can pay to have somebody at a hardware store cut the pieces, and only need a drill.

To do that, you'll need 4 pieces per frame, and some flat L-shaped corner braces. You can butt-join the pieces, i.e., just cut them straight and butt them together like this:

Code:

+--------------+------------------------------------------------------------+
|              |                                                            |
|              |                                                            |
|              |                                                            |
|              |                                                            |
|              |                                                            |
|              |                                                            |
|              +---------------------------------------------+--------------+
|              |                                             |              |
|              |                                             |              |
|              |                                             |              |
|              |                                             |              |
|              |                                             |              |
|              |                                             |              |
|              |                                             |              |
|              |                                             |              |
|              |                                             |              |
|              |                                             |              |
|              |                                             |              |
|              |                                             |              |
|              |                                             |              |
+--------------+---------------------------------------------+              |
|                                                            |              |
|                                                            |              |
|                                                            |              |
|                                                            |              |
|                                                            |              |
|                                                            |              |
+------------------------------------------------------------+--------------+



(This would be a very small frame, if the pictures was to scale.)

Use flat L-shaped steel corner braces to hold them together, like this:
Code:

+--------------+------------------------------------------------------------+
|              |                                                            |
|  +-----------------------+                              +--------------+  |
|  |                       |                              |              |  |
|  |   +-------------------+                              +----------+   |  |
|  |   |       |                                                     |   |  |
|  |   |       |                                                     |   |  |
|  |   |       +---------------------------------------------+-------|   |--+
|  +---+       |                                             |       |   |  |
|              |                                             |       |   |  |
|              |                                             |       |   |  |
|              |                                             |       |   |  |
|              |                                             |       +---+  |
|              |                                             |              |
|              |                                             |              |



The spirally-symmetrical but not-mirror-image-symmetrical pattern of butt joints makes the L braces work better. (It may probably a good idea to make the top frame go one way, and the bottom frame go the other.)

Position the L braces on the top frame near the centerlines of the strips. On the bottom frame, put them a little further out, so that the inner edge of the strip will clear the gasket rather than resting on it, with a little room for error in bringing the frames down on the gasket. Attach them with appropriate-diameter wood screws for the L-braces. (The braces may come with screws, but make sure they're not too long, and don't poke through the wood strips.)

You'll want L braces that are pretty big, for stability but not so big that they get in the way of where you want to put your clamping bolts.

Put holes through both frames, with countersunk clamping bolts glued into the bottom frame, as for the plywood frames.

IMPROVING WOOD FRAMES

Besides making the top frame grippier, you may want to make the bottom frame seal better to the plastic. Sanding it smooth helps.

If you want the best possible seal, you can use tape each time you clamp the frames together, taping the plastic to the bottom frame. The tape will get icky after a few uses, however, and you'll need new tape.

(Another solution would be to coat the gripping part of the bottom frame with heat-tolerant rubber, such as silicone. I don't know if anybody's tried that, or how easy it is to get it very smooth.)

If you're worried about repeated baking in an oven being bad for your wooden frames, you might want to paint them with white oven paint. (That is, paint designed to be used on the insides of ovens---it's available at most hardware stores.) Nobody seems to bother doing this, but you might want to, especially if you used cheap wood for your frames and they start to show signs of charring.

Oven paint will insulate the surface slightly, but more importantly, white oven paint will make the frames more reflective, so that they absorb less infrared radiation from oven heating elements, and don't heat up as much while they're in the oven. (Don't use the black oven paint; it makes things heat up faster.)

In general, be careful with with painting any surface that will come in contact with hot plastic; many paints make the plastic more likely to stick, and some can't take the heat. By default, don't do it; don't paint your platen, and if you paint your frames, paint them on the outside only, with high-temperature paint.

ALUMINUM FRAMES

I'll describe two basic kinds of aluminum frames that are commonly used in homebuilt vacuum formers.

The first is more appropriate for a vacuum former using a gasket to seal around the platen; it's also more rigid, and better for somewhat larger frames. (You'll need a hacksaw and a drill to cut the aluminum, but don't worry---aluminum is very soft as metals go, and you can drill it fine with a regular drill, and cut it by hand with a hacksaw.)

The second kind of is especially cheap and easy to make, if you have a hacksaw and a miter box, and it works well for fairly small frames, for systems where the plastic seals directly to the platen edge. (I'll discuss those in a later chapter.)

(If you're a scrounger, you may be able to find some old window screens at a scrap yard or in a dumpster, and cut the frames down to size; that makes them really cheap.)

To some extent, you can mix and match, using one for the top frame (where no seal is required) and the other for the bottom frame, which is why I'll discuss both types here.

One reason I present several options is that many things work, and you can use whatever's cheapest and easiest for you. For example, some of my frames are made out of metal that I bought at a scrap yard, as scrap aluminum, paying a fraction of what I'd pay at the hardware store for new metal. (It's only a few bucks here and there, but I find it satisfying and I like poking around scrap yards to find bigger and more valuable things I can use for other purposes.)

ALUMINUM FRAMES with C Channel and/or Angle Metal and binder clips

One way to make aluminum frames is with aluminum extruded with an L-shaped cross section. That's sold in 3-, 4-, 8-, and/or 10-foot pieces in hardware stores such as most Lowe's or Home Depot stores.

It's nice to use a piece long enough to make a whole frame, so that you can bend it in three places and only have to join the ends (with screws or hand riveting).

You may have to look around to find a hardware store that sells pieces long enough to make whole large frames---a three- or four-foot piece won't make a very big frame---but it may be worth stopping at a couple or calling around. (Even within a chain of hardware stores, different individual stores may offer different selections.)

A common way to make aluminum frames is with angle metal (with an L-cross section), like this:

Code:

                   |                                          |
                   |  <----------- top frame ------------->   |
              -----+                                          +-----
                ================== plastic sheet ==================
              -----+                                          +-----
                   |  <----------- bottom frame ---------->   |
                   |                                          |



In this setup, the thin edge of the bottom frame is what rests on the plastic and seals to it.

The two frames are held together by binder clips around their horizontal parts (and the plastic):

Code:

                   |                                          |
          ******** |                                          | ********
binder    *   -----+                                          +-----   *    binder
 clip ->  *     ================== plastic sheet =================     * <-  clip
          *   -----+                                          +-----   *
          ******** |                                          | ********
                   |                                          |



For small frames, say 8" x 12", 3/4" angle metal 1/16" of an inch thick is probably fine.

For medium-sized frames, say 12" x 18" or so, you may want to use 1" L metal 1/16" of an inch thick, or 3/4" L metal 1/8" thick.

For larger frames, you may want to use 1" L metal 1/8" thick.

One nice thing about the binder clips is that you can use as many or as few as you need, where you need them. For thin plastics, you only need a few. (For a 12 x 18 frame, about six---one on each short end and two on each long side.) For thick plastics, which are more likely to pull out of the frame when you drape them across the buck, you can use more.

Another nice thing about the binder clips is that they have convenient handles which can be pivoted back out of the way, or if that's still in the way, you can just squeeze them and take them off, leaving the clip in place. (I've done that when I had a tight fit in an oven.)

To bend the frames, first use a hacksaw to cut through the horizontal part of the L where you want to make a corner. Then you just bend the vertical part around something with a sharp corner, trying to keeping the bend perpendicular to the horizontal part so, that each frame is flat. (It doesn't have to be perfect---the frames are slighly flexible and don't have to be absolutely flat to clamp together.)

Each corner should look something like this, where we're looking down at the frame:
Code:

           +-----------------------------
           |
           |
           |
           |
+----------.-----------------------------
|          | .---------------------------
|          | |
|          | |
|          | |
|          | |
|          | |


Here you can see that the slot cut in the horizontal part has widened to a 90 degree gap at the corner when the vertical part was bent.

Some people recommend that before cutting the horizontal part, you drill a 1/4" hole where the end of the cut will be, flush with the vertical part. This is supposed to reduce the stress on the metal when bending it. (I think the real benefit comes from removing most of the horizontal part for a little way on either side of the cut, right up against the place where the vertical part will be bent.)

For 1/8" metal, you may want to bend it around something with a radius of about an eighth to a quarter of an inch, to reduce the chance that it cracks while bending. (For 1/16" thick aluminum, that doesn't appear to be necessary; thinner metal is much more easily bent, and it's hard to get a really sharp bend anyway.)

That's how you make three of the corners, anyway. To make the fourth corner, where one end of the L-metal joins the other to make a closed frame, leave a couple of extra inches of metal for an overlap. Make the fourth corner like the others, then cut off the horizontal part of the extra two inches. Attach the remaining two-inch vertical part to the vertical part of the other end,by drilling holes through both and putting screws or hand rivets through them. (If you don't know about hand rivets, a.k.a. pop rivets, don't worry about it. Just use machine screws, i.e., bolts, with nuts.) On the bottom frame, you may want to use J B weld to seal the joint, being careful to make the bottom edge solid and smooth where it will meet the gasket.

Notice that in the diagram, the plastic does not extend all the way across between the horizontal parts of the frames. In general, it shouldn't. You only need about a half-inch for gripping the plastic, and having more overlap would just waste plastic, so the cuts you make in the metal for the corners should be one inch closer together than the dimensions of your plastic sheets.

Also notice that in this scheme, the plastic sits up pretty high---as high as the size of angle metal you use, and that the thin bottom edge is what rests on and seals to the gasket.

It's not clear to me whether using the thin edge for a seal works better or worse than something broader. On one hand, it means that a local ripple or dimple in the gasket could make a leak, even though a broader area of aluminum would cover the depression entirely and not leak. On the other hand, it concentrates the same force on a narrower strip of metal, so the narrow edge may push harder against the gasket and seal better. (Again, nobody's done experiments that show how well this works.)

At any rate, my personal preference is to do something different, if only to reduce the height of the lower frame. Rather than use L-metal for the lower frame, I prefer C-channel. (Also available at hardware stores along with the L-metal.) I also cut a 90-degree triangular notch in the horizontal parts, rather than a simple slot. This ensures that the sealing surface narrows gracefully at the corners, which I think may help ensure it seals well to the gasket; it also makes the cut corners stick out less and be less likely to snag things.

My preferred frame construction is very similar, except that you have to cut through two sides of a three-sided piece of metal, and you get something like this, with an L-metal upper frame and a C-channel lower frame:

Code:

                   |                                          |
          ******** |    <- L (angle metal) upper frame  ->    | ********
binder    *   -----+                                          +-----   *    binder
 clip ->  *     ================== plastic sheet =================     * <-  clip
          *     ---+                                          +---     *
          ******** |       <- C channel lower frame ->        | ********
                ---+                                          +---


Notice that the C channel and the L channel are not the same size. The L channel is bigger and maybe thicker, and provides most of the rigidity. The c-channnel can be smaller; it only has to be rigid enough that clamping it in particular places spreads the clamping force halfway to the next clamp. (A small amount of flexibility in one frame may even be a good thing, ensuring that one frame conforms well to the other, while still distributing the clamping force broadly enough.)

Of course, if you just want to go to the hardware store and get something, and do something simple, you can use thick C channel for both frames. (Or L channel.) That works fine, too.


ALUMINUM FRAMES with Window Screen Framing (and binder clips)

Another way of making aluminum frames is with window screen framing material, which is basically a thin aluminum tube with a rectangular cross-section. It's designed for making simple rectangular frames, and there are prefabricated corner braces that slide right into them. You just cut the framing material to length---and slide the corner braces into the tubes.

Try to get metal corner braces; many places only sell plastic ones, apparently including most Lowes and Home Depot stores. You might try a True Value or an Ace. (My local True Value and Ace both sell aluminum angle braces for windowscreens.) Or you can find them online.

Common window screen framing material from hardware stores is about 3/4" wide and comes 8 foot lengths, in different thicknesses, typically 5/16", 3/8", and/or 7/16". I use 7/16" because it's substantially more rigid. (You might not think so, but rigidity is proportional to the cube of the thickness, so 7/16" is about twice as rigid as 5/16", which is rather flimsy.) Not all places carry all thicknesses; I get mine at my local Home Depot, but I use aluminum corner braces from a True Value; they're 3/8" braces but they fit fine anyway.

(I think some people use the plastic corners that are sold everywhere---maybe because they don't know that aluminum ones are available. Plastic corners probably work okay for thin plastics, which don't need to be in the oven very long, but I haven't tried it. I often bake thick plastics slowly, so I wouldn't trust the plastic ones not to soften up too much in the oven.)

When using the aluminum corners I use, you have to miter-cut the framing material, so you'll need a hacksaw and a miter box. Be sure to clamp the aluminum in place in the miter box; if you don't, it will be difficult to saw, as well as producing a sloppy cut.

One very slight drawback of the window screen framing material is that there is a channel on the inside edge of the frame for a "spline" (a rubbery strip that holds the actual screen in place.) This channel is useless for our purposes, and reduces the gripping surface of the aluminum a little bit. There's still plenty of area left, though, and it just amounts to costing you a little bit of usable plastic area. (Unfortunately, that channel has to be on the inside edge, or the corner braces I use work right won't work; there's a tab that fits into a slot in the edge material, which only goes in one way. For other kinds of corner braces, you may be able to orient the framing material the other way, putting the channel outward where it costs you nothing at all.)

If you use window screen frames for both the upper and lower frames, and hold them together with binder clips, you get something like this:
Code:

                       *                                         *
     ******************                                           *****************
     *    +------+                                                     +------+   *
     *    |      |                                                     |      |   *
     *    +------+                                                     +------+   *
     *    ======================... plastic sheet ...==========================   *
     *    +------+                                                     +------+   *
     *    |      |                                                     |      |   *
     *    +------+                                                     +------+   *
     ******************                                           *****************
                       *                                         *


Here I've shown the binder clips in a little more detail. They are roughly C shaped with a rolled edge where the handle attaches. That can be problematic for a system where the frame seals to a gasket, as described in this chapter. If you do use them (as I sometimes do), you should not clamp the clamps too far out---the rolled edge will stick down and may interfere with the gasket seal. (I find that my gaskets can usually cope pretty well, and seal behind the rolled edge, but this can't be good and may sometimes be a problem, so it's best avoided.)
And of course you must remove the handles, at least on the bottom side, or they will make a dent across the width of the gasket and make a path for the air to leak in.

The clamps themselves can do this, even if you take the handles off; you must make sure that the bottom part of the clamp is flush with the bottom frame, so that there isn't a gap between the clamp and the frame for air to leak through there. (There's still a very slight potential leak at each clamp-bottom edge, but in my experience this is not a problem for a low-vacuum system. Vacuum cleaners can pump a lot of air, and can keep up with slight leaks like that without a problem.)

A somewhat better solution, especially for a high-vacuum system where leaks are more important, is to use C-channel for the lower frame, and clamp the frames together like this:

Code:

               *                                                         *
   ************                                                           ***********
   *      +------++                                                   ++------+     *
   *      |      ++                                                   ++      |     *
   *      +------+                                                     +------+     *
   *      ======================... plastic sheet ...==========================     *
   *      +------+                                                     +------+     *
   ************  |                                                     |  ***********
               * |                                                     | *
          +------+                                                     +------+
            +-------+                                               +------+
            |||||||||                <- gasket ->                   ||||||||
            +-------+                                               +------+
------------------------------------... platen ...--------------------------------------


Here I've also shown the gasket, to illustrate something else: if you use C or L metal to make the lower frame, the inside edge of the frame must hit the gasket, or you won't get a seal. (For L-metal, there's only a narrow strip that meets the gasket at all, and it's on the inward side. For C-channel, there's a broader strip on the sides, but not at the corners.)

I've also shown the windowscreen-frame upper frame with an irregularity on one corner. That's the channel for a spline to hold a windowscreen in. It doesn't matter much whether you orient the frame so that that's upward, or so that it's downward, but you should realize that it doesn't provide a sealing or gripping surface. Size your frames according to the flat part, and your frames will match where they clamp together.

(It doesn't matter if they don't match exactly, or if you line them up exactly when clamping. You don't need more than a half inch of gripping or sealing surface for a fairly big frame, and you can do fine with less for small frames. If that's not enough to keep thick tough plastics from slipping, you need more clamps closer together, not more area of overlap.)


SINGLE RIGID FRAMES WITH CLAMP BARS, AND MIX-AND-MATCH FRAMES

If you use a bunch of different-sized frames, the frames may end up being the dominant cost of a siimple vacuum former---both in materials and in time. You may not want to construct a pair of frames for each size, and may not even have to construct a whole frame---just two sides.

Mix and Match Frames

If you're using windowscreen frame material, you can mix and match the side lengths, and create a new frame size from old pieces. For example, if you have 6" x 8", 8" x 12", and 12" x 16" frames, you can take the 12-inch sides from those frames, and plug them together to make 12 x 12 frames, or take the 6-inch and 16-inch sides and make 6 x 16 frames. You can make frames that are both sized and proportioned to what you're making.

One Rigid Frame Plus Clamp Bars

You also only need one rigid frame that's actually attached all the way around. You don't really need an upper frame at all---just strips on each side to help hold the plastic down, spreading the force of the clamps. The plastic does not need to seal to anything on top, so the "frame" corners there don't have to be connected---you can just butt strips together and clamp them in place.

So, for example, if you have parts for one 4 x 8 frame, but not two, and you also have some 6" and 8" parts, you can use larger parts to "frame" the top of the plastic, with part of each strip sticking out around the edges, like this:

Code:

                                               +-+
                                               | |
                                               | |
+----------------------------------------------+ |
+-----------+----------------------------------+ |
          | |                                  | |
          | |                                  | |
          | |                                  | |
          | |                                  | |
          | |                                  | |
          | |                                  | |
          | +----------------------------------+-+------+
          | +-------------------------------------------+
          | |
          | |
          +-+


The requirements for these top-clamping strips are very loose; they just have to be at least long enough. They don't have to be the same stuff you make your rigid frames out of---they can be fairly flimsy, if you use enough clamps, and can have holes in them. Old scraps of metal struts or trim are fine.

(They don't even have to be at-least-long-enough, really. If you have a piece that's a little too short, you can use a binder directly against the plastic on top, and clamp a strip across the rest.)

Of course, having a bunch of individual strips you have to clamp down is awkward. For any size that you use many times, it's more convenient to have a pair of frames and just clamp them together around the plastic.

Adjustable Clamping Frames with Attached Clamp Bars

If you ever get very serious about vacuum forming a variety of things in different shapes, sizes, and plastic thicknesses, you may want to make a set of adjustable clamping frames with attached clamp bars. That's how many industrial thermoformers work, to make it very quick to load and unload plastic, and fairly quick to change sheet dimensions. That's really beyond the scope of this introduction, but I thought I'd mention it and sketch the idea.

[This digression will eventually be moved to a later "chapter" or whatever, if/when that gets written.]

The most common scheme is to have frames that are adjustable to any length in one direction, with a fixed width in the other. Suppose, for example, we want to be able to form plastic that's 12 inches wide in at least one direction, but may be 5 x 12 inches, 12 x 12, or 12 x 20 inches, etc.

We can have an adjustable bottom frame consisting of two long sides, with two short sides spanning the gap between them to create a 12-inch width. The short sides are movable inward or outward to make small short fat rectangles, 12-inch squares, or larger tall skinny rectangles :

Code:

| |              | |        | |              | |        | |              | |
| |              | |        | |              | |        | +--------------+ |
| |              | |        | |              | |        | +--------------+ |
| |              | |        | |              | |        | |              | |
| |              | |        | +--------------+ |        | |              | |
| |              | |        | +--------------+ |        | |              | |
| +--------------+ |        | |              | |        | |              | |
| +--------------+ |        | |              | |        | |              | |
| |              | |   OR   | |              | |   OR   | |              | |
| |              | |        | |              | |        | |              | |
| +--------------+ |        | |              | |        | |              | |
| +--------------+ |        | +--------------+ |        | |              | |
| |              | |        | +--------------+ |        | |              | |
| |              | |        | |              | |        | |              | |
| |              | |        | |              | |        | |              | |
| |              | |        | |              | |        | +--------------+ |
| |              | |        | |              | |        | +--------------+ |
| |              | |        | |              | |        | |              | |


The pairs of short spanning bars can be interchangeable, for example giving widths of 8, 12, 16, and 20 inches. This allows an enormous variety of sizes and proportions, approximating any rectangle within a couple of inches in one direction, and as close as you want in the other. (Or within half an inch, if the short bars can connect to the long ones at discrete points at one inch intervals.)

In this kind of scheme, each bar has a full-length clamping strip at the top. (For the long bars, much of this strip usually "goes to waste" because there's only plastic in the middle part---but who cares?) Each clamping strip is attached to the bar with a hinge, so that it can be flipped up in one operation, rather than tediously clamped with several little clamps.

MAKING THE GASKET(S)

Now you need to decide whether you're putting your gasket directly on the platen, or making a removable gasket on its own sheet of something flexible. If you want it removable, find a sheet of something thin and smooth, preferably flexible plastic that's not brittle but not rubbery. (I use some thin vinyl I coldn't find another use for.) Cut it to the size of the gasket you'll make, plus an inch. (Or if it's almost the size of your board, half an inch.) That edge will be what you tape down to seal it to the board. Now cut a hole a couple of inches in diameter at the center. That will let the air out through the hole in the board.


There is a wide variety of gasket materials available. The ideal one would be very durable and heat-tolerant, like a silicone rubber foam. Unfortunately, I have no idea where to get strips of silicone foam, and sheets of the stuff cost a fortune, so we'll use something cheap, as most people do.

Get some 3/4" wide rubberfoam weatherstripping from the hardware store. It'll probably be 1/4" or 3/8" of an inch thick; either is fine. Be sure to get enough---the perimeter of a small rectangle is longer than most people intuitively think, and if you're making several, do the math. It's not terribly heat tolerant, but then, it won't have to take much heat for very long at a time, and will last a while.

Now figure out how big you need your gasket to be. Remember that for L- or C-channel bottom frames the center of each side of the gasket should line up with the inner part of the frame, where it can seal all the way around.

The foam weatherstripping is backed with waxed-paper stuff that you peel off to reveal expose the sticky side. Don't peel that off until you're ready.

Most people just cut and butt-join the strips for each side. I like to notch the foam with a triangular cut most of the way through---but not all the way---and bend it closed like a miter cut. Either way, make your cuts so that the sides are slightly oversized, so that the joints will snug up.

The foam is stretchy and compressible, and it's easy to make a mistake by compressing the foam in some places and stretching it near the ends, so that the parts that are supposed to butt together pull apart instead. You may want to carefully smooth it down, one side at a time, and only make the cuts when you see where the foam will reach the end. (And make it 1/8" "too long," so that you can compress it and attach the end, skipping a few inches, then smooth it down from there.)

If you mess this up, don't worry about it. A little wiggliness is okay, and a little gap can be filled. If you really screw it up, just peel the stuff off and try again.

Once you've got the foam down okay all the way around, you may want to seal the joins with flexible glue like rubber cement or silicone caulk. (For system using only a vacuum cleaner for suction, it probably doesn't matter much unless there are visible gaps; for a high-vacuum system, it's worth it.)

If you made a reusable gasket, tape it in place. Masking tape is fine. Carefully smooth it down along each edge, making sure you don't have wrinkles across the edge of the removable sheet for air to leak through.

Now you've made a vacuum former. You rock!


NOTES ON MATERIALS AND SOURCES

Most of a simple vacuum former can be made of stuff that's free or very cheap. (The same goes for a professional quality vacuum former I [will/may] describe in a later "chapter.")

For most parts, the dimensions are not critical, and the material properties are not extreme----you can adjust the design here and there, so stuff from a dumpster will do fine. If you like dumpster diving, notice the big dumpsterish things at construction and remodeling sites, and dive a few of those.

You may also find plastics you'll want to try vacuum forming, in forms you don't expect. I've got an enormous roll of 1/8" thick blue plastic that once once the side wall of an above-ground swimming pool, which somebody left on a curb as bulk trash. Old light diffuser ceiling panels can be very cool---vacuum-forming textured plastics can give beautiful results. (And hide flaws in your molds.)

Visit it the Goodwill Blue Hanger store if you have one nearby, and if you have a Habitat For Humanity Re-Store, definitely check it out. That's usually more efficient than hitting a bunch of normal thrift stores. If there's a local scrap / "metal recycling" place that lets people poke around the piles of stuff and buy stuff by the pound, you're in good shape.

If you're building a small former with an eye toward making a bigger, heavy-duty former later, definitely think ahead and start stockpiling g
_________________
Paul (a.k.a. Dr. Crash)

Tired of buying cheap plastic crap? Now you can make your own! www.VacuumFormerPlans.com


Last edited by drcrash on Wed Jul 04, 2007 2:22 pm; edited 4 times in total
Back to top
View user's profile Send private message Visit poster's website
drcrash
Guru


Joined: 04 Sep 2006
Posts: 705
Location: Austin, Texas

PostPosted: Mon Dec 18, 2006 2:56 pm    Post subject: missing part at end Reply with quote

Looks like the last section got truncated... here it is again:


INFORMATIONAL RESOURCES

Books:

Doug Walsh's inexpensive little book "Do It Yourself Vacuum Forming For the Hobbyist" is a great first book on vacuum forming. It does what it says on the tin. Similar information is available free on the web now, scattered around, but spending a few bucks on Walsh's book is a good idea.

If you have a bit of money to spend on plans and parts, Walsh also sells plans for nice, relatively inexpensive professional-quality vacuum formers, and heating element kits.

Thurston James's "The Prop Builder's Molding and Casting Handbook" is a classic, and definitely worth reading. (You can probably find it in your local library, or get it on interlibrary loan.) It's not mostly about vacuum forming, but it has a chapter that gives plans for a large pro-quality vacuum former with its own oven. (More on that below.)

Web Sites:

At this writing (Dec. 2006), the best web site I've found for discussing DIY vacuum former design and construction is www.tk560.com. There is an article on building a vacuum former from Thurston James's plans, with cost-saving substitutions by Jim Egner (the site administrator/moderator). This is the cheapest way to build a tried-and-true large vacuum former. There are little introductory and demo videos and everything.

There is also a discussion forum where people discuss variant and alternative designs they've built, vacuum forming materials and techniques, etc. (If you register there, be sure to post at least one posting saying hi, or you're likely to be deregistered in a spambot-purging sweep.) Highly recommended.

The vacuum forming discussion forum at www.hobbymolding.com has useful information as well, including several long postings by me (drcrash), some of which amount to rough drafts of chapters, or parts of chapters, of this [projected] book[-like thingie].

The vacuum forming discussion forum at www.CNCzone.com has both experienced commercial thermoformers and hobbyist folks; it's not as active as tk560.com (at this writing) but there's very good information and advice to be had there.

Other Introductions to DIY Vacuum Formers and Vacuum Forming on the Web

If you don't like my "thorough," verbose style, I don't blame you, and you may want to start with a shorter, breezier introduction to do-it-yourself vacuum forming, and maybe come back to my stuff if/when you get interested in details and alternatives.

There are several nice ones on the web, giving one way to make or do each thing. Some are just around, on several sites and mailing lists:

Chad Veich's "Basic Vacuum Forming" on www.rcuniverse.com is good, and has interesting information in the comments. It's oriented toward making radio control aircraft parts, but the basic principles are there. Chad's posts in that thread and others are excellent, especially if you want to make nice-looking clear parts. (Such as model plane canopies, but really anything clear.)

The Vacuum Table tutorial on www.studiocreations.com describes a dead simple board-with-a-hole-in-it vacuum former with a shop vac, a kitchen oven, and one way to make wooden frames. It's oriented toward making fairly large pieces such as costume armor breastplates, with minimal equipment. I'd rather make my own oven than try to use a kitchen oven for oversized plastic, but if you want to try it, grab yourself a heat gun and go for it.

George Gassaway's model-rocket-nosecone-oriented tutorial (somewhere I forget...) is very brief and says the basics.

Ralis Kahn's plans on www.halloweenfear.com inspired me (and many others) to build a little "over-and-under" machine of my own---that is, one with its own oven directly above the forming table. His uses a little rectangular Sunbeam barbecue grill, which unfortunately is now hard to find. Still, have a look---see how simple, cheap, and pretty a neat little vacuum former can be? (But if you do decide to build something like that, see my postings on tk560 about evening out the heat from the grill heating element, or alternative "heat" (infrared) sources.)

[I'll add others as I remember them...]

Some Rough, Preliminary Versions of More Advanced Topics

If you actually like my writing style, and are interested enough in my take on more advanced topics, you might want to check out/ wade through stuff I've posted in various forums, notably

The posting/thread on "Avoiding Webbing" on www.rcuniverse.com (about how to vacuum form fairly tricky shapes).

Various postings/threads on www.hobbymolding.com, on "platen design issues" (about how to make a low-volume, edge-sealing, lotsa-holes platen), "two-stage" "plumbing" for high vacuum systems, etc.

Various postings/threads/comments on www.tk560.com, including "Fun with Fluorescent light diffuser ceiling panels" (about forming textured plastics), "fun with craft foam (EVA foam)" (about forming rubbery craft foam), "Conventional (IR) Oven Design," "Convection Oven Ideas," "vac sources, pipe sizes, flow rates, and scaling up or down" (about how to adapt plans for high-vacuum systems to different situations), "An Idea for a Drop-down Frame" (about plastic raising/lowering mechanisms for large over-and-under machines) "fixed sunbeam grill over/under's heat distribution," etc.

Or you may just want to browse the forums, and ask questions, until I organize more of that material into better-baked, more or less coherent chapter-equivalents.

ACKNOWLEDGEMENTS

I gratefully acknowledge helpful and illuminating information and advice from:

Jim Egner (TK560 himself), Charlie Mann TK (TK386 of TK386.com), Tony (TK4063), Harley Guy, Blind Squirrel, Plasticman, PropSculptor, and others too numerous and list mention over at tk560.com.

Various folks at hobbymolding.com and CNCzone.com (Thanks DC, and "Hi, Mrs. Harper!")

Thurston James, for his book, and Doug Walsh of www.build-stuff.com for his, which would have saved me a lot of time and effort if I'd gotten it sooner, and still taught me some cool things.

And most of all Mykel, my lovely and talented wife and coconspirator.

Naturally all errors, and idiosyncracies and foibles are due to my own fallibility and intractability.
_________________
Paul (a.k.a. Dr. Crash)

Tired of buying cheap plastic crap? Now you can make your own! www.VacuumFormerPlans.com
Back to top
View user's profile Send private message Visit poster's website
Plasticman
Expert


Joined: 08 Jul 2006
Posts: 109

PostPosted: Mon Dec 18, 2006 6:12 pm    Post subject: Reply with quote

Man, you must type like 80 WPM! How do you do that?!
Back to top
View user's profile Send private message
drcrash
Guru


Joined: 04 Sep 2006
Posts: 705
Location: Austin, Texas

PostPosted: Tue Dec 19, 2006 8:36 am    Post subject: Reply with quote

Plasticman wrote:
Man, you must type like 80 WPM! How do you do that?!


Years of practice, I guess. Decades, even. I taught myself to type when I was 11 or something, and that was over 30 years ago.

BTW, I didn't write that in real time---it took me several hours.

I can type about as fast as I can think of things to say, though. Not as fast as I can talk. I can talk pretty fast. Smile

(My first semester teaching college, I wrote 350 pages of notes for one class, writing the book as I went along. Whew. That was kinda stupid, but it came out pretty well.)

The unusual skill I have is doing ASCII art fairly quickly, another old habit.
_________________
Paul (a.k.a. Dr. Crash)

Tired of buying cheap plastic crap? Now you can make your own! www.VacuumFormerPlans.com
Back to top
View user's profile Send private message Visit poster's website
Display posts from previous:   
Post new topic   Reply to topic    www.TK560.com Forum Index -> Vacuum Forming & General Stuff All times are GMT - 6 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum

phpBB "skin" by DewChugr


Powered by phpBB © 2001, 2005 phpBB Group