Make a good, cheap, upgradeable sheet plastic vacuum former

 by drcrash
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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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Step 1: Understand the design

Our vacuum former consists mostly of

(1) a board (called a "platen") with a hole in the middle of it,
(2) a vacuum cleaner that sucks air through that hole,
(3) a pair of frames we can clamp together around the edge of a sheet of plastic, and
(4) a kitchen oven.

To use it, we'll do three basic things:

(1) heat the plastic in the oven until it's soft and rubbery and stretchable
(2) stretch it over the shape we want to copy, and
(3) suck it down around that thing, and let it cool in that shape

In more detail, we'll

0. (SETUP)

0.a. Support the board on something near the oven. The support(s) can be pretty much anything, or any convenient pair of things that is reasonably sturdy, allows us to route the hose to the vacuum cleaner without kinking it, and can be put very near the oven we're using.

0.b Put some things in the oven which we can support the plastic-holding frames on. (Glasses made of actual glass, for instance.)

0.c. Preheat the oven. This usually gives us more even heat.

0.d Position some object that we want to shape plastic over on the board, over the hole, but with some spacers under it, so that air can flow from around the the object, under it, and to the hole in the board.

1. (HEAT)

1.a Clamp a sheet plastic between the pair of frames and support it on three or four things in the oven (such as glasses made of actual glass)

1.b Wait a few minutes for the plastic to get hot and rubbery and stretchable. For most plastics, we can tell how stretchable it is by how much it sags under its own weight. When it sags about the right amount, we know it's ready.

2. (FORM)

2.a. (Turn on the vacuum cleaner, open the oven, and) QUICKLY but carefully remove the plastic from the oven with gloved hands...

2.b. ...stretch the plastic down over the shape we're copying, until the frame meets the board, creating a kind of "tent" of hot rubbery plastic over our form and stretching down to the board, and...

2.c. ...let the vacuum cleaner suck air out from under the "tent," by sucking air from under the form, and in turn from around it. This will suck the stretched, rubbery plastic inward into the desired shape, in about one second, and the plastic will cool enough to solidify in the new shape in about 10 to 20 seconds.

To make this work well, and flexibly, we'll add a few basic enhancements:

1) We'll put a foam rubber gasket on the board, the size and shape of our plastic-clamping frames. That way, when we stretch the plastic over our mold, we can press the frame against the gasket to make a seal. When the vacuum cleaner sucks air from around the mold, it will do a better job because it's not sucking air through any little gaps between the frame and the board.

2) We'll make the gasket removable, so that we can use different-sized gaskets (and plastic-clamping frames) for different-sized sheets of plastic. The obvious benefit of this is you can waste less plastic if you make different-sized things. A less obvious benefit is that it helps you use odd-sized scraps that you get from cutting the larger size out of a sheet of plastic. A much less obvious benefit is that you often get better results for certain difficult-to-form shapes, by using plastic that is somewhat bigger than the thing you're making, but not a whole lot bigger.

(I won't explain that here, but if you're interested you can check out this thread on www.rcuniverse.com, about "webbing" problems and ways to avoid them: http://www.rcuniverse.com/forum/m_5086453/anchors_5086453/mpage_1/key_/anchor/tm.htm#5086453 One of the best ways is to use plastic sheets about the right size for your project.)

Making the gasket removable is easy. Instead of sticking the self-stick foam rubber directly to the platen (board), well stick it to a slightly oversized sheet of something flexible---such as thin plastic, and tape that down to the board.

3) We'll make our frames out of pieces of aluminum windowscreen frame material, with internal aluminum corner braces. That will let us mix and match a few side lengths to make frames of different sizes and proportions for different projects.

4) We'll use a 3/4" galvanized floor flange (plumbing fitting) under the hole in the platen, as part of our connection to the vacuum cleaner hose. This will let us replace the vacuum cleaner with a more powerful---but surprisingly cheap---vacuum system later, if we want. A more powerful vacuum system lets you form thicker plastic and still get good detail. (If you know you'll never need to do that this, you could just make the platen hole the size of your vacuum cleaner hose, or some attachment that fits it, and glue the hose or the attachment permanently to the hole. That would be cheap and easy, but you would lose flexibility for later upgrades.)

If you've seen other homemade vacuum formers, you've likely seen "vacuum boxes" several inches thick covered with pegboard. Don't make one of those. You don't need a bunch of holes in your platen; One big one works at least as well if you're only forming one object at a time, and if you want to distribute the vacuum across several smaller molds, there are other ways of doing it. (Many industrial vacuum formers use one-big-hole platens.)

Thick "vacuum forming boxes" are likely to collapse if you ever add a powerful vacuum system---and to reduce the vacuum system's effectiveness, because the air inside the box has to be pulled out.

(If you decide later that you really want a many-hole platen, you should make a thin "sandwich construction" platen; you can use your one-hole platen as the bottom layer of the "sandwich," so starting with a one-hole platen is a good way to go.)
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feyr says: Apr 29, 2009. 9:11 PM
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.
mackamitsu in reply to feyrJan 30, 2013. 10:51 AM
why not buy a plumbing adapter to size for both the platen and inlet.
snowpenguin says: Jun 27, 2009. 12:54 PM
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*
mackamitsu in reply to snowpenguinJan 30, 2013. 10:45 AM
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.
CB2001 says: Jun 9, 2010. 10:44 AM
Is using your kitchen's oven safe? The reason I ask is because i live in an apartment building, and I know hot plastic gives off fumes. Not only that, I use the oven regularly for eating food. The last thing I want to do is risk my health and the health of others.
hanelyp in reply to CB2001Oct 1, 2010. 9:42 PM
Do it right and the plastic should never get that hot. For this kind of forming you want the plastic soft, not burnt.
CB2001 in reply to hanelypOct 1, 2010. 10:42 PM
Really? I heard that plastic lets off fumes when its heated up, no matter if its soft or burnt.
mackamitsu in reply to CB2001Jan 30, 2013. 10:37 AM
a lot of times the smell the so called online "experts" say are plastic fumes, are nothing but the release agent used in the factory. If you feel the need to use a mask, don't use dust filters, go to a safety supply store and get a proper mask.
shotgunefx says: Jul 2, 2007. 4:06 PM
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 ;)
hybryd in reply to shotgunefxJan 1, 2013. 7:53 PM
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) in reply to shotgunefxJul 2, 2007. 5:18 PM
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.
shotgunefx in reply to drcrashJul 2, 2007. 9:36 PM
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) in reply to shotgunefxJul 2, 2007. 11:14 PM
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.
shotgunefx in reply to drcrashJul 2, 2007. 11:25 PM
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".
hybryd says: Jan 1, 2013. 7:51 PM
#12 3/4" flat head wood screws worked well for me here.
pyrogreasemonkey says: Sep 30, 2012. 7:29 PM
you could make a hard case for your phone! just raise the phone off the forming table about 2mm so the plastic can make a lip around the rim so the case stays on.
jgrout says: Sep 1, 2012. 9:06 PM
drcrash: I built a vacuum forming machine based on your design. It can be seen at http://7hillsmake.org/2012/09/02/adventures-in-vacuum-forming/
It turned out nicely, I think. Thanks for you instructable it was a big help.
gnarledwolf says: Apr 8, 2012. 1:59 PM
I just tried this project. I used wood frames in two sizes. the larger one was the for rent sign plastic from lowes and several smaller ones the size of small figurines, and the plastic was the thin poly folders from staples, which I cut into individual pieces. After some experimentation, i found 400 to be a perfect temp for my oven... preheated, then about 60 seconds turned the plastic clear and caused it to dip... we then formed it over the pieces were were molding. Amazing! That never gets old! I got some webbing on the smaller, thinner plastic, but was still please... currently making ice out of them to see just how good the mold is. I stuffed polymer clay into one and with a little work, it replicated the figure nicely. the most impressive was with the "for rent" sign from Lowes. We used a larger set of holders, made of wood, and the figure of an inca statue about 1 foot long and 5 inches deep. the plastic cooked for the same time as the thinner plastic... and we were amazed at the perfect copy it made of the statue! next we plan to do that in ice too... just to test the result... but it looks perfect... no webbing at all! Thank you so much for posting this... I'm blown away! My project cost me $60.... plus the cost of the plastic.
foobear says: Mar 25, 2012. 11:27 AM
Can soda bottle plastic be used for this sort of purpose? I tried a makeshift vacuform using a metal strainer, duct tape, shop vac and heat gun combo but only succeeded in causing the plastic to warp up and twist around, it did not get sucked down over the mold...

keenan says: Oct 17, 2007. 5:28 PM
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 in reply to keenanOct 17, 2007. 5:31 PM
sorry I meant oven timing duh
drcrash (author) in reply to keenanOct 18, 2007. 5:03 AM
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.
cmjake007 in reply to drcrashOct 24, 2011. 2:07 PM
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
innerbubba in reply to cmjake007Mar 18, 2012. 9:53 AM
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?
ToweringProductions says: Jan 6, 2012. 4:14 PM
I GOT SOME quick questions! if there is a large or really odd sized mold you'd like to form how would you do that with out making to many week points in the plastic? i mean weird size like a shoulder bell or pauldron that may have open areas and is relatively long. the other question is would it work if i formed in onto stiff foam like insulation board or would the plastic adhere to it?
-cheers!
ezarate says: Dec 2, 2011. 4:00 PM
very nice! im planning on making this but in a larger scale to make copies of halo helmets.

but where can i buy the Plastic from????(not online)
and how much does it coast????

please respond as soon as possible thanks
RGalliath says: Nov 24, 2011. 9:02 PM
You can add perferated partical board suspended over the vacume hole in order to create equall suction over the whole thing.
swidkid says: Nov 24, 2011. 6:23 PM
Does the website at the end of the video work for anyone? It didn't for me.
kaikudo says: Nov 24, 2011. 5:38 PM
Iis the possible to get a heat gun and smooth out the cracks? or sandpaper? D:
qwertyboy says: Nov 24, 2011. 7:20 AM
I love it. Now you can make your own cheap plastic crap!
RangerJ says: Oct 27, 2011. 6:11 AM
Outstanding project. I've added this to the short list of projects I want to work on soon.
jbaker22 says: Jul 8, 2011. 11:02 AM
Doesn't heating plastic give of gasses that cause cancer?
micjwelch in reply to jbaker22Sep 12, 2011. 12:08 PM
Burning plastic can be dangerous, but simply heating it to make it softer doesn't put off any nasty chemicals.
swilson28 says: Aug 5, 2011. 3:50 PM
I had no idea it could be that easy. The people at http://sibeautomation.com want thousands of dollars for a machine that does this. Now I'm considering making one myself.
justindunham says: Jul 29, 2011. 10:35 AM
Awesome that you can build one of these so cheaply! I used 5/16" windowscreen frame material with no problem, and I also used plastic corners (both were available on Amazon). I blogged about my experience building it here: http://justindunham.net/2011/07/building-a-vacuum-forming-machine/. Thanks for writing this!
DehLeprechaun says: Apr 29, 2011. 8:19 PM
this design seems fairly straight-forward could i replace the simple hole with peg board and build a table for it? i want to know what thiknesses of plastics it could use/mold.
xw239 says: Mar 26, 2011. 12:00 AM
I made this vacuum former like in the instructable, but when i hook my shopvac up to the box, there is very little to no suction coming from the holes. please help!
cardboarddude says: Mar 17, 2011. 7:15 PM
Do you think i could make a decent mold of a paper pepakura helmet using this method?
whowes in reply to cardboarddudeMar 24, 2011. 5:13 PM
I think...I'm going to be using this to vacuum form a visor. I know a lot of people on the 405th do, but you'd definitely have to harden the helmet, not try to just mold around paper.
ATOMIC_RACOON says: Mar 3, 2011. 6:17 PM
What about if my original piece is exactly the size I want? Should I make a silicon mold and vacuform the inside of that, or coat the inside of the vacuform with a liquid plastic?
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