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Make a good, cheap, upgradeable sheet plastic vacuum former

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Tired of buying cheap plastic crap? Now you can make your own!

Or you can make nice and surprisingly sturdy plastic stuff in amazing shapes, amaze your friends with your technical prowess, and be the life of the party.

Vacuum forming is a technique for shaping sheet plastics into 3D shapes, which you can do at home, easily and cheaply. And it's fun. It's the easiest way to make an infinite variety of shapes in plastic, or to make molds for casting shapes in other materials, such as concrete.

The basic technique is to

0. clamp a sheet of plastic to a frame (such as a windowscreen-type aluminum frame)
1. heat it in an oven (such as your kitchen oven) until it's soft and rubbery
2. stretch it over a convex mold of an interesting shape (such as a life cast of your sweetie's face), and
3. suck the plastic inward onto that mold with a vacuum system (such as your household vacuum cleaner)

Once the plastic cools, you pull it off the mold and trim off the excess plastic, leaving a copy of whatever shape you sucked the plastic onto.

In this instructable, I'll show you how to make a cheap but good vacuum former, using mostly things you have around the house, or can buy very cheaply. The whole thing shouldn't cost more than about $30 to $50, maybe less depending on what shortcuts or substitutions you choose, and what materials and tools you have lying around. It also shouldn't or take more than an hour or two to make. (Plus a shopping trip to a home improvement store and an office supply store, and letting some silicone cure overnight; you can use epoxy if you're in a big hurry and want to do it all in an evening.)

Here's a movie of the vacuum former in action:



Relatively few people know about vacuum forming, or how easy it is. They're mostly radio control model builders---who use it for making thin plastic parts for airplanes, or bodies for cars or helicopters, or hulls for boats---or they're Star Wars fans who use it for making their own costume armor.

It's unfortunate that vacuum forming know-how is mostly limited to these little niches, because vacuum forming can be used for many purposes, artistic and practical. If you like making stuff in general, and especially if you like non-rectilinear stuff that doesn't look "homemade," you should know how to vacuum form.

You can use vacuum forming to make:

1. intermediate molds for modifying and combining sculptural shapes (this allows you to sculpt in whatever medium is easiest, and transfer the shapes to plastic, making one copy or many)
2. sturdy custom parts out of thick plastic to protect delicate machinery. (Using cheap homemade equipment, I've vacuum formed shells from 1/4" thick plastic that are sturdy enough to stand on.)
3. three-dimensional, internally-illuminated signs from scintillating textured plastic
4. flexible, cushiony custom liners from thermoformable foam
5. relief sculptures of various kinds
6. molds for casting chocolates, soaps, candles, or concrete relief sculptures
7. decorative architectural reliefs, or decorative shells that can be reinforced for structural purposes
8. stage props and costume parts in hard plastic or soft foam,
9. zillions of things you'll probably think of.

Industrially, vacuum forming is used for making all kinds of things, from disposable plastic cups and lids to sinks and hot tubs and McDonald's golden arches to full-sized boat hulls. (If you've never seen a 30-foot sheet of plastic sucked into a boat shape in a few seconds, trust me, it's pretty cool.)

For vacuum forming at home, the main limitation is usually space for the equipment---the size of your vacuum former is proportional to the size of plastic sheet you need to form. The $30-50 vacuum former described here doesn't take up much storage space at all, and can handle thin plastic sheets as big as will fit in your oven.

For larger stuff, you need a custom oven---not very difficult or expensive to make, but a little bigger all around than the plastic it will heat.

For thick plastics (more than about 3/32" or 1/8" thick, depending on several variables) you often need a stronger vacuum than a vacuum cleaner will provide, and again the cost and size of the equipment are roughly proportional to the size of plastic sheet you will be forming. The cost can be under $50 for a high-vacuum system for thick plastic sheets up to about 12" x 18", using a converted bike pump, or an electric air pump of some sort from a thrift store. (Such as a kitchen vacuum sealer, a tire inflator air compressor, or a "nebulizer" air pump.)

The vacuum former described here will work very well with an inexpensive high vacuum system, getting professional quality results for thick plastic, for under $100. If you want a standalone vacuum oven, so that you can use it somewhere besides your kitchen, you can make a medium-sized one (12 x 20 inches) for $30.

For now, let's make a good fast cheap vacuum former that you can do a lot with, using your kitchen oven and vacuum cleaner; it's mainly a board with a hole in it, which you can store on a shelf. You can soup it up later, if you want.

 
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snowpenguin4 years ago
Can you use a toaster oven to do this, with smaller plastic sizes? I'm basing the whole project off of one mold, but I'm sure I'll use it a lot. I plan to use either soda bottle plastic of milk jug plastic, heated to stay flat. I would then either iron or heat-gun several sheets together for strength. Great 'Ible, 4.5*
drcrash (author)  snowpenguin8 months ago
I don't know if laminating multiple layers of bottle plastic will work well. You may be better molding single sheets and laminating the results after they're shaped.

A single layer of soda bottle plastic often works really well and eaisly for small stuff like most model plane "bubble canopies," and for smallish food molds like chocolate molds or jello molds. (It's "food safe" plastic unless you burn it.)

You don't need to do anything special to flatten it---just cut the ends off the bottle, so that you're left with a cylinder, then split that, unroll it, and clamp it between appropriately-sized frames. When you heat it, it will relax and act just like a flat sheet.

drcrash (author)  snowpenguin8 months ago
Yes, you can use a toaster oven for small stuff. Lotws of RC modelers do.

If you're making something really small, pretty much any toaster oven will work fine. If you're making something that uses plastic that barely fits in the oven, it's nice to have on that heats particularly evenly. The ones with a single heating strip above and below may not heat particularly evenly---two above and two below may be better.

I got a great toaster oven for little stuff for a few bucks from a Goodwill store.

I used a dollar store toaster oven for one project, making chocolate molds for a special cake. I used food grad plastic for that. Some dollar stores have cheap plastic containers with nice thin lids.Don't forget about ebay either.
shotgunefx6 years ago
I've got a question, where did you get the window screen brackets? Most of the places I see them have plastic corners which proves to be problematic in thermoforming ;)
Based on the age of this instructable, they may not have carried them before, but my Home Depot now carries the aluminum frame corners.
drcrash (author)  shotgunefx6 years ago
I use some from my local True Value hardware store, but I don't know if other True Values carry them. (I've also seen them at a local Ace Hardware.) Step 2 gives online sources.
Thanks for the quick reply, I don't know how I missed that first go around, my apologies.

I made a quickie vacuum former awhile back out of parts laying around the house, I had an expanded metal shelf laying around that worked for a base.

I took a different tact with connecting the vacuum that seemed to work well. I used a flexible sink tailpipe that happens to fit my shop-vac perfectly. For mounting it to the MDF, I just used expanding insulation. The few times I used it, it worked well, how well it would hold up over extended, heavy use, I'm not sure. ( Vacuum connection )

The only problem I had was with the frame. I kept meaning to get back to it, but never did , well until now that is ;)

Thanks again.
drcrash (author)  shotgunefx6 years ago
That will work fine if you only ever want to connect that vacuum cleaner to it; I like having the platen be an interchangeable part. The floor flange has the advantage that you can unscrew the nipple from it and it's pretty low-profile; you can store the platen on a shelf without several extra inches of stuff sticking out awkwardly. The compression fitting on the end of the thing you used is nice. I'll have a look at those and maybe find a good way of adapting from the floor flange to a compression fitting that fits small shop vac hoses. Thanks.
Like I said, it was kind of just thrown together with what I had on hand. I never considered a floor flange. If you want to make a fitting, you can get an 1-1/2 (or 1- /12 x 1-1/4 depending on your vac hose size) PVC "desanko" female pvc fitting, then glue an 1-1/2 x 3/4ips bushing into it, then use a short 3/4ips nipple to mount it to the floor flange. It's been awhile since I worked in plumbing supply, desanko is what plumbers call them, but they might be under a different name at the depot and similar. I believe they are also commonly called "trap adapters".
n0ukf6 years ago
It appears from looking at your face mold that you, like I, have facial hair (beyond just eyebrows and lashes). How do you mold yourself with that, without having to shave first?
Gnome n0ukf5 years ago
I saw a video about it: You have to use "cholesterol hair conditioner" by applying it to the hair, eyebrows, beard, etc. to help with the release.
TechDante6 years ago
i've done this sort of thing but was just wondering what sort of plastic you were using and how long was it in the oven
drcrash (author)  TechDante6 years ago
For thin plastics like 1/32" or 1/16", you generally want to adjust your oven heat so that it takes a couple of minutes to heat the plastic to the right sag point. (Start low and work up until you get the heat level about right.) That's so that it doesn't sag too fast for you to notice when it's ready, and you have a little slack in how fast you pull it out. For thicker plastic, like 1/8 or 1/4", you want it to take a minute or two per millimeter, so that you don't burn the surface before the heat soaks through to the middle. I vacuum form a bunch of kinds of plastics. In the video, I'm using HIPS (High Impact Polystyrene a.k.a. HIS for High Impact Styrene). In the 2nd and 3rd pictures in Step 11, that's textured acrylic from a 2 x 4 foot fluorescent light diffuser panel for suspended ceilings. (From Home Depot.) It is also easy and fun to vacuum form craft foam (EVA foam), but the technique is a bit different because it doesn't sag. (See my web site.)
excelent, just what i need thanks. now just have to get myself the parts.
HaZe326 years ago
this is kinda off topic to the vacuum but how do u make that mold of your face i want to make plastic masks of my face (i dont know y) and i need to make a mold cause im not stickin my head into hot plastic and vacuuming out all the air lol
drcrash (author)  HaZe326 years ago
My wife did it---it's hard to do to yourself---by putting alginate on my face to capture the fine detail, and then making a mother mold around that to hold the overall shape. It's not difficult. (DON'T put plaster directly on people's skin, unless you really know what you're doing. The plaster heats up, and if it's too thick, you can actually burn somebody... and you happen to have a problem getting it off, that can be A Bad Thing. Plaster can also form very sharp edges where two surfaces meet, and cut right through flesh. Ooops.) There are various instructions for lifecasting and specifically face casting on the net... we looked at several before actually doing it and I don't remember which ones were the best. There's at least one over at www.theeffectslab.com, and probably some over at www.lifecasting.com If you go to our site, www.VacuumFormerPlans.com, you can find a link to threads on how we use alginate both for face casting and for casting sculpts to make masks. It's not a not detailed how-to, but it shows the basic process and few simple tricks we use to make casts that are especially suited to vacuum forming. (Like molding in a few vent holes so that the plastic will suck in around the eyes, nose, and mouth. Greased wooden skewers work great.) For a typical face cast, we use about $5 worth of alginate, $1 or $2 worth of plaster bandages, and $7 worth of water putty (to cast the positive). You can get water putty at the hardware store, and plaster bandages from a craft store. (Hobby Lobby has decent prices.) We use the slow-setting alginate from www.pinkhouse.com
ovechkin0806 years ago
What kind of plastic do you use and where could I get some.
drcrash (author)  ovechkin0806 years ago
That depends a lot on what you want to make.

The most common plastics for beginners, and also common for non-beginners are High Impact Polystyrene (a.k.a. HIPS, or High Impact Styrene, or HIS) and PETG. HIPS is usually opaque, and PETG is crystal clear. They're both pretty cheap and pretty good, and easy to form.

I'd recommend starting with plastic between 1/32 and 1/16 inch thick. (Or .030" to .060" or so.) Thinner plastic cools so quickly you may have trouble getting it to the platen and formed before it cools. Thicker plastic is harder to form without high vacuum, and is more expensive.

The most economical place to buy it is usually a local sheet plastic supplier. You can buy a 4 x 8 foot sheet of thin plastic for what a few small sheets would cost at a hobby shop or craft store. You can probably roll it up to get it into your car. (While it's still flat, thin plastic is flexible. Forming it into a 3D shape makes it much more rigid.) Look in the phone book and call around, to find a supplier that has no minimum order, or a low one like $25. Some places don't want to talk to you if you're not buying at least $100 worth of stuff. Others are happy to sell you a sheet or two of thin plastic. Unfortunately you generally have to call around to find out which is which.

Online, you can get sheet plastics from places like TAP Plastics and Professional Plastics.

I often vacuum form textured plastic light diffuser ceiling panels from Home Depot or Lowe's, which come in 2 x 4 foot sheets. The styrene ones are easier to form than the acrylic ones, but harder to find, and more fragile.

I also vacuum form craft foam from craft stores. (Hobby Lobby has good prices on craft foam---a 12-pack of 12 x 18 inch sheets 2mm thick is $4.00. ) That's a little different from most plastics, though, because it doesn't sag when it gets hot enough to form.

You can find links about vacuum forming diffuser panels and craft foam on my web site. ( http://www.vacuumformerplans.com )

Acrylics can be a problem because they absorb moisture from the air, and if you heat them, you get little bubbles. In my experience with diffuser panels, the bubbles have been small and don't show much. (They don't show at all for the translucent white stuff, just for the clear.) To avoid the bubbles, you may need to "pre-dry" acrylics, baking them at 200 degrees for a half hour to a couple of hours, depending on the thickness. That drives off the water.

Two other commonly vacuum formed plastics are ABS and polycarbonates (like Lexan (TM)). They both can absorb moisture from the air and require pre-drying, too.

I'd stick with HIPS or PETG, starting out, to avoid having to deal with that. (Craft foam doesn't have a problem with moisture.)

You can get a piece of PETG about 6" x 13" (IIRC) by splitting cutting the ends off a 3-liter soda bottle, splitting it, and unrolling it. A lot of RC plane "bubble canopies" are made of pop bottle PETG.

I'm working on another Instructable, with detailed instructions for vacuum forming and plastics sources, but that probably won't be done for a few weeks.

rerat6 years ago
Not an expert or anything..but wouldn't many small holes, opposed to one large one, yield more even suction?
I believe rerat is right, in all the vacuum formers I've seen (both commercial and home-made) the base consisted of many smaller holes. Without the small holes, it would be nearly impossible to get the level of detail that you would normally get.
drcrash (author)  Erik Lindemann6 years ago
No, that is not right. In fact, you may get better detail with a one-hole platen than if you just plop your mold flat on a many-hole platen. Once the plastic has mostly sucked down, it covers the holes that the mold is NOT over, and they do zero good. If the mold sits flat against the holes under it, it covers and blocks the ones it IS over, too, so you have NO holes operating well. That restricts airflow at the crucial time for getting good detail. (It usually doesn't matter much, but it can matter some.) That's why I recommend putting a layer of windowscreen down, even if you do have a many-hole platen---that makes it work as well as a one-hole platen with spacers. With sufficient space under the mold for the air flow you need, a one-hole platen with the mold over the hole works as well as any platen could. Many small vacuum forming machines sold to non-professional thermoformers do come with many-hole platens. It think that's mostly a matter of marketing expectations---more holes seems like better. It is what hobbyists expect, and what they copy. (And it is marginally more convenient than a one-hole platen for making multiple things at a time; all you need is a single layer of windowscreen under all the molds to make it work perfectly.) I did do research on this, talking to several industrial thermoforming people and a physicist. They all agreed that one hole is as good as many, if you use proper spacers. Most of the industrial machines I've either have a one-hole platen or no platen at all, and one professional thermoformer I've talked to said he'd used a half-dozen models of industrial machines, all with one-hole platens. I don't have statistics, but I'm pretty sure one-hole platens are pretty popular in industry because they work just fine. One place that more holes does matter is in the mold itself. If your mold has significant concavities, you may need vent holes through the mold to let the air out. (More holes in the platen doesn't help with that.)
Now I didn't see you mention the use of spacers in your instructable, maybe I just missed that. That makes sense. But you see, the use of very many tiny holes should work just fine seeing as each hole acts independently from the rest. By logic, it shouldn't matter if its one hole or many holes just as long as you have spacers with the one hole.
drcrash (author)  Erik Lindemann6 years ago
Right. Many holes, in themselves, don't hurt, and they are actually a little more convenient---you can use very short "spacers" such as a single layer of window screen to keep the mold from blocking the holes under it, and to keep the plastic from sucking down flat over the holes around the mold.

You can get the same effect with a one-hole platen by making some grooves in the top of the board, radiating out a few inches from the hole. (Don't make them too long---if you do, you'll have problems sealing small tape-down sheets on your platen.) If you have a router, that only takes a few minutes.

The grooves ensure that the mold can't sit flat over the hole and block it---air can still be sucked through the grooves. Adding one layer of window screen is still good, to keep the plastic from sucking down into the grooves and blocking them, and to let air flow across the surface of the board from anywhere into a groove.

Here's a posting over on www.hobbymolding.com that sketches how to make a many-hole platen that won't collapse under vacuum and doesn't hold a lot of useless air:

http://www.hobbymolding.com/hm_forum/phpBB2/viewtopic.php?t=418

That's a fine thing to do, but it doesn't get you better results, would more than double the time to construct the vacuum former, and (if your holes are spread out too far from the middle of the board) it means you need big tape-down sheets to cover most of them when you want to use a small gasket.

A good compromise, if you want to go to the trouble of making a many-hole platen, is to have a about 40 1/8" holes in an area about 7 inches by 9 inches in the middle of the board. That's plenty if you have a single layer of window screen, and it allows you to cover the holes with a small, cheap tape-down sheet (like a small $1 flimsy FOR SALE sign) when you want to put down a small gasket.

That will let you put multiple molds anywhere on the platen; you don't need holes under a mold, because a wide swath of windowscreen will allow plenty of air to flow to the middle of the board and into the holes. You don't need a mold over the holes, either, because the screen will keep the plastic from sucking down flat and blocking them. And if you pick up the screen, you can still tape your tape-down sheets down to the non-holey area around the holey area.

That would combine all of the advantages of a one-hole platen and a many-hole platen.

Thank you, very informative.
drcrash (author)  rerat6 years ago
Not really. The air under the plastic, around the mold, acts as a "plenum" to even out the pressure, all by itself. (I can explain that if you want.) The only place the pressure may be significantly different is right around the hole, under the mold. The idea that many holes "even out the suction" is a myth. Most many-hole platens are not designed properly for that goal. To even out the pressure more than happens naturally anyway, you'd need restrictive platen holes, and a significant pressure differential across them. That would make the platen holes a bottleneck, so it's generally avoided. The typical pegboard-topped box made by hobbyists would be a particularly ineffective plenum, because the holes are way, way too big. (That's okay, though, because you don't need that effect anyway. The problem with pegboard is that it collapses under high vacuum, unless it has lots of supports, and it's generally not worth that.)
marcwolf26 days ago

Many many thanks for the suggestion of folded metal flyscreen for the base.
This has always been a hinderence re drilling lots of holes.

Peter_Pan2 months ago

For a while I've been planning to build a vacuum form machine to build recessed control panels. If you've ever seen an acoustic guitar with build in electronics, the controls are usually on a recessed panel like this. Or, you might see a shape like this on the backs of wooden loudspeaker cabinets, where the wires connect. So initially i thought this would be such a simple shape. After all, the molds would be simple blocks of wood crafted to the depth and size of the panels I'd need. Then after forming, I'd only need to trim the plastic, but include maybe a 1/4" lip all around. To use these panels, i would then cut the shape of the original mold into the guitar, and insert my panel. A small screw in each corner of the lip would hold it in place. What could be simpler, right?

Well NOT so!!! Because I now realize that whether I used holes in my platen, or a window screen as you suggest, the "lip" surrounding my mold is probably going to look awful, having the window screen pattern now molded into its surface! I'm not sure what to do about this. I guess I could just live with the screen pattern and try to sand it off
later, but that sounds labor intensive, and might still look lousy in
the end.

I suppose I could make a more complex mold that includes the lip, by attaching the original panel block mold to a thin flat piece of wood, a total of 1/4" bigger on all sides. But I think that will create a new problem, because that lip area is, of course, flat. So once the plastic is drawn to the edge of the lip, it will block further vacuum from getting into the inner corner, and I'll have poor definition. Kind of a catch 22!

The only thing I can think of would be to take the flat thin piece of wood that will become the lip, drill a big hole in the middle of it, then cut a small piece of window screen the size of the center block. If I can then attach the center block to the flat piece of wood with the small piece of screen in between, right over the hole, this should allow air to continue to be drawn, even if the plastic does form a seal around the edge.

What do you think? I know there's no way to do this stuff without some experimentation, but I definitely don't want to waste a lot, and would like to know I have a sound technique for getting the shape I need, while avoiding the screen pattern.

bgepp16 months ago
this is great - btw - where do you buy the plastic (the sheet you put in the oven)?
feyr4 years ago
I am looking into making this but I want to use my 5hp 12 gallon shopvac that is in the garage since I only have an upright vacuum for the house. It has a large 2.5" hose on it and I was wondering what size I should drill my hole into the platen? Based off your statement of using a larger hole than your hose I was thinking of a 3" hole. Bringing some pipe down and using one of those rubber reducers with hose clamps on it to create the seal between the two parts. Also on a vacuum like that how thick do you think I can work with and would it be too powerful for thinner pieces? Thanks for this awesome writeup! I am looking into using 1/16th, 1/4 or possibly 3/16 thick acrylic sheets to make an automotive headlight trim.
drcrash (author)  feyr8 months ago
For a shop vac, you don't need a larger diameter hole that the hose---they use huge hoses, ridiculously oversized for most purposes. (But useful if you're sucking up fist-sized hunks of lightweight stuff.)
drcrash (author)  drcrash7 months ago
And don't forget that shop vacs are no great shakes for vacuum forming. They generally DO NOT suck any harder than a canister vacuum, and they're awkwardly big with awkwardly big hoses. Ratings like "5 hp" are a bullshit. A shop vac doesn't generally draw more current than a good household vacuum, so it CAN'T generate more power without blowing your fuses or flipping your circuit breakers.
why not buy a plumbing adapter to size for both the platen and inlet.
keenan6 years ago
Do you have any tips about timing? Specifically 1/32" clear styrene? my piece is 24" long, 3" at the widest and 3.5" at the deepest tapering at the ends.
keenan keenan6 years ago
sorry I meant oven timing duh
drcrash (author)  keenan6 years ago
You'll want to experiment a bit, starting around 225 and working UP to the right temperature setting for your oven and your plastic, raising the temp setting 25 degrees or so until the plastic starts to sag in about a minute or two (for thin plastic like 1/32" or 1/16"), or a few minutes (for thick plastic). For thin plastic, the main issue is that you don't want the plastic to sag faster than you can react, once it starts to sag. For thick plastic, you don't want to heat the surface faster than the heat can soak through to the interior. (As with cooking anything else, too much heat will burn the surface before the inside is done.) It should take a minute or two per millimeter of thickness for the heat to soak through, depending on the plastic.
hi- very nice project, well thought out and applied !! i have a problem i'm hoping someone can help me with. i'm doing some prototype work and for the life of me am unable to find a source for plastic sheeting that is within reason. i need a source for two types of plastic sheets. the first one has to have the properties of being aprox. at least 18"X18" and have a little strength to it. the second one about the same size or bigger and similar to the to the dome plastic used in grocery store bakery items. what i have found in searching is the price is simply wacko. i am now considering re-purposing things like large pvc water pipes, and such. as far as the dome stuff i do not have any ideas that are good enough. anyone out there have any thoughts ?? thanks
drcrash (author)  cmjake0077 months ago
You can get 4 x 8 foot sheets of plastic from a local plastics supply store---they sell sheets of various plastics to sign stores, contractors who use them in construction, etc. It's much cheaper per square foot than buying plastic from a hobby store or hobbyist supply place.
I've been looking, too. So far I've only found
http://www.widgetworksunlimited.com/Styrene_Thermoform_Plastic_s/51.htm

but they seem a little on the pricey side. I'm still searching for a wholesaler. Anybody got any leads?
drcrash (author)  keenan7 months ago
For thin plastic, I'd generally adjust the heat until the plastic softens up and sags enough (about 1 inch per foot of span the short way) in about two minutes.

You can heat thin plastic faster than that (and industrial systems do), but keeping it fairly slow is nice in a low-volume low-end home setup, for a couple of reasons: (1) it gives you a little more slack for misjudging the time, and (2) it lets the oven air circulate a bit and even out the heat, after opening the door to put in the plastic, or if you open it to check on the sag. (It's better to look through an oven window if you have one.)
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