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Vacuum Forming for Free

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I recently needed 12 fake candlestick phones for a musical ("Crazy For You"). Real candlestick phones are incredibly expensive, and even replicas were too much for my budget. All 12 needed to match as well. I decided to make them all.

I wanted to match the shape of the bases to the real thing, but it would take too long to sculpt 12 bases, and casting them would be too expensive. It looked like it could be vacuum formed. I've worked with plastics in the past, but never with a vacuum former, though I've seen some in action. I couldn't spend a lot of time or money building a vacuum forming machine for this project; I figured if I liked what it was capable of, I would build a nicer one after this project based on what I learned.

After researching what I needed, I found I could build one for free. I already had the necessary components in my shop. I figured many prop makers will already have these parts as well, so I am sharing how I did it.
 
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Step 1: Gather your materials and tools

For me, this vacuum forming machine was free, but that's because I already had all the tools and materials. These include:
* a shop-vac
* a heat gun
* some scraps of MDF
* some scraps of lauan
* spring clamps
The tools I used were a drill press, a table saw and a small hand saw, a combination square and a pencil. I also used a bit of glue and some grid paper. 
You can substitute some of the tools used as well as the precise materials needed. The shop-vac I had cost $25 new, and the heat gun was $25 new as well, both from the big-box hardware store. So if you had to buy everything for this, it would only be $50 for the equipment and a couple bucks for the materials. Even if you never vacuum form again, you can still use the shop-vac for cleaning your shop and the heat gun for other projects.
The plastic I was using was a thin sheet of Sintra, which is a brand of expanded PVC. It was about 2-3 mm thick, and I cut it into smaller squares using a utility knife and a straightedge. 
agis681 year ago
this is very interesting ible and also some good food for thoughts....thanks for sharing. I will try for some experiments. I own a vacuum of Philips that reaches about 8 BAR (That it says the label) (philips triathlon model). this plastic for molding has any special feature and comes with various thickness? how thick is yours....



thanks
8 BAR? If one could achieve a perfect vacuum, this would amount to slightly over one BAR or about 30 inches pressure. This barometric pressure is often seen on Tee Vee when the weather is announced. A vacuum pump could never "pull" more than this because the air pressure of our atmosphere that is actually doing the pushing hardly goes above one BAR. Standard atmospheric barometric pressure is given around 1013 millibars, or 1.013 BAR.

As another example, If a person 50 ft above a jar of water sucks a "perfect" vacuum using a 50 ft straw, the highest the water will go up the straw is about 34 feet (at sea level). Any water column taller than 34 feet would weigh more than the weight of the atmosphere (14.7 lbs/sq in) that is pushing the water upward. Imagining a one inch by one inch square tube filled up to 34 feet will weigh about 14.7 pounds if one uses the weight of water (about 62.4 lbs/cubic foot). A simple calculator works wonders here.

This info is not necessary for the project here but the info revealed here might be interesting to some...
Eric Hart (author)  agis681 year ago
The plastic I was using was .030" thick. It has no special features other than it has to be a thermoplastic (one which becomes flexible when heated and rigid when cooled back to room temperature). Styrene is one of the cheaper types, making it popular with prop makers doing vacuum forming. Others include PVC (vinyl), Kydex (a brand name for an acrylic/PVC copolymer), ABS, CAB, and acrylic (plexiglass). You can also use PET and polyethylene, which you can get from soft drink and milk bottles, but these are extremely difficult to paint or glue to.
Fantastic! Every prop maker is always trying to find new ways to get stuff done. This is a great bit of info! Thanks for sharing!
This is an interesting instructables about DIY vacuum forming. You really have a good feel on this topic, and the way you wrote about it made it both interesting to read, and informative at the same time. Thanks a lot for sharing. Vacuum Forming UK
robin671 year ago
I'm a little late in posting but modifying the reed valves on a small cheap automotive compressor might do the trick for producing a strong vacuum.I have seen a very small unit on a job site used to align two pieces of granite together for counter-tops,and it was no larger than a 12v air compressor to fill your tires .I repair my own compressors and found they use reed valves to maintain constant psi.why not reverse the process for vacuum,. it might require some mod.like an added check valve.I'm curious if anyone has tried it yet.
sconner11 year ago
I love it as a get started cheap method.
like you said if you find you want more better capability then you can justify spending more money and time to build a better one.
zacker1 year ago
so i take it that more heat and a more powerfull vac would make this alot better? i have a 16 gallon wet / dry vac and a good heat gun, what is the max size plate i can use?
Eric Hart (author)  zacker1 year ago
A more powerful vac would make it better, but from what I've read, a larger shop vac is not more powerful than a smaller shop vac. Larger and more powerful shop vacs move more air in less time than smaller ones, but the amount of vacuum pressure is still between 2 and 6 inches of Mercury.

Also, while a heat gun is usable on smaller pieces like I was doing, when you start getting bigger, you want more of an even heat, like with an oven. Even with a powerful heat gun, you'll end up heating one section until it is pliable enough for forming, and when you move to heat up another section, that first section will cool back down. I had a thought of building a small "hot box" to hold my plastic while I heat it (maybe just an enclosed box lined with aluminum foil) so the heat will not dissipate so quickly as I use my hot air gun. Still, my next step would be to build a better heating system because using a hot air gun really limits the size and thickness of plastic you can use.
Good thoughts Eric. I can see the vac thing as you say,. I have the big shop vac and a smaller (9 gallon) ridgid shop vac and i tend to like the smaller one more..I never even thought to see which one has more suction.

A Hot box..thats an idea. like you say, build it, line it with something shiny like tin foil, use that tin foil tape to close all the seams then, build a bigger version so you can insulate the smaller one, put the bigger one over it so you shouldnt lose any heat. You would probably need one heat gun on each end though. I wanna try this and see what I can make....lol
Bill WW1 year ago
Very nice, Eric!

This may be enough incentive for me to buy a vacuum pump. Or, who knows, maybe make a a multi-stage shop vac? Maybe a high speed drive on my old shop vac parts? OK, I'll start slow, use the one I've got.
Then I will have to think of something to vacuum form.

Excellent video.
AlphaRomeo1 year ago
Cool project indeed - from your experience can we use the PET bottle material? Do you think hair drier would give enough heat to soften this material?
Eric Hart (author)  AlphaRomeo1 year ago
It is a thermoplastic, so you should be able to use PET in vacuum forming. I am not sure if a hair drier gives enough heat to soften it. If it does, I would think it would take a while to soften it, and it may be difficult to keep the whole sheet of plastic heated evenly. But if you already have a hair drier, you may as well test it out and see how well it works.
Thanks for your reply - what is the kind of temperature that you get.
You said above that PET and polyethylene are extremely difficult to paint or glue to, well one can use marker pens -
I do see some other applications too - such as custom made packing.
I like the idea of Josehf Murchison's idea of using 200 watt floodlight for heating.

Wonderful and simple DIY -
This an interesting process. Where do purchase the plastic?
Besides distributors in most large cities, McMaster-Carr stocks a huge variety of plastic sheet materials.
What thickness did you use for the phones?
Eric Hart (author)  Dickerson8881 year ago
I would guess the plastic I'm using is about .080 inches thick, maybe less.
Eric Hart (author)  Eric Hart1 year ago
Scratch that last comment, I actually had my plastic measured and it is .030 inches thick.
rusty01011 year ago
A possible shortcut is to use pegboard as your forming surface.

you will want to seal smooth any non-through holes at the edges, a piece of aluminum tape along that area may do the job.

If you need to vacuum form larger objects, it's going to be a lot faster than drilling out a 2'x2' board. However you will probably want to put in supports between the pegboard and the bottom of the vacuum chamber to prevent the pegboard from flexing.

Since most pegboard is substantially similar to masonite, it should not be significantly impacted by the heat.

If you find that the spacing on the pegboard is too wide, you can always grid out additional holes between each of the holes in the space you need the work done in.

Finally if you need to vacuum form smaller pieces of plastic than your form would normally allow, a sheet or two of masonite could be used to mask off portions of the vacuform board that will not have plastic over them.
Eric Hart (author) 1 year ago
UPDATE: I checked out my local plastics supplier today to get some more plastic to finish these phones. It turns out what I was using was NOT Sintra, but styrene. I was using .030" styrene, and all they had was .040" sheets, so that is what I got. I hope it is not too thick to use on my machine, but I only have 4 more to pull.
What a great Instructable. I too occasional built props as well as doing scenic design and construction for schools and local community theaters. I've always been fascinated with vacuforms. I will archive your instructable for future reference.

Years ago, while searching props on the web, I came across a website that offered instructions for building an actual vacuform table, complete with heating coils and a hinged frame for moving the heated plastic from the heat bed over to to the platen/vacuum bed. It was build to one of the plastic industry's standard sheet size (I believe about 48"X60"). Sadly, by the time I was in a position to build one, I could no longer find the website.

I was also in need of candlestick phones, years ago, for a production of "Cabaret", and I ended up building them out of parts cannibalized from thrift store table lamps. I wish I'd had your instructable then.

Well done. Keep up the good work!

TheStarWizard

PS
If anyone comes across instructions for building a large vacuform table that doesn't require putting the plastic in your stove's oven, please let me know. Thanks!
It would be good to note that when you cut the hole for the vacuum hose to fit in the bottom board, that you make sure that the hose will not come into contact with the perforated top board. One may want to put a couple of spacer nubs under the perforated board to ensure the end of the vacuum hose stays back from it otherwise it could possibly only suck from the holes in front of the hose - and not from the other cut holes.
Nice phone prop start.
I would fill it with cement actors can be rough on props.
How do you like my vacuum molding machine?
I have made sabots and a scoop for my loading scale with it.
Most of my molds are sinking molds so I use a 200 watt floodlight to heat the plastic for molding light plastics.

Joe
vac,m(2).JPG
I know from experience that you can heat plexi-glass in an oven to manipulate it into different shapes. Do you think it would be possible to form plexi in a vacuum former?
Virtually any thermoplastic (and that includes Plexiglas (R)) can be vacuum-formed. Some materials are easier to work with than others; Plex is one of the more difficult, but nowhere near as bad as UHMW. Look up the properties of the material you are considering. http://machinedesign.com/term/basics-of-design-engineering/bde-materials is a good place to start.
Vodika1 year ago
After looking at all this, I am posative I can use this to mold my leather for costom cases, thank you
maxhuey1 year ago
$99 Shark Vacuum cleaner is quite useless as a vacuum cleaner but should work great for this project. Let me explain, Shark vacuum as you often see in their TV ads shows how capable this vacuum is but in reality, the motor pass a low CFM of air with very high negative pressure - a mistake many vacuum machine manufacturer did thinking this will make the vacuum work better. This is also why you see them advertising how strong the "suction" is "when in sealed vacuum" where no work is performed. For a vacuum system to work properly, it needs to pass a very high amount of air through, look at the commercial carpet cleaner truck, their vacuum not only produce negative pressure but pass very high amount of air. We called CFM - Cubic feet per minute. Now in vacuum forming, we do not need large amount of air to go through but instead we need the negative pressure the vacuum can create. Just happened the shark vacuum can do this quite nicely.
Kinnishian1 year ago
I'm getting a 3D printer in a few weeks, and I was wondering if you have ever used ABS as your imprinted object. My concern of course would be the ABS becoming squished as you heat up the plastic that is being molded. have you had any experience with that?

I'd be up for experimenting with ABS parts that have ice-filled cavities, to keep the abs object cool.
Eric Hart (author)  Kinnishian1 year ago
I suppose the ABS may lose a bit of definition. You can try coating it with a high heat paint. You may also try a method I've seen at professional shops which have to vacuum form over fragile objects. First, vacuum form a thin sheet of plastic with a low melting point over your ABS object. Next, turn it upside down and fill the cavity with a hard plaster (like Hydro cal). Remove the plaster piece when it is set; you now have a buck that can withstand the heat and pressure.
It seems like that might do the trick, if the ABS doesn't hold on its own. Thanks! This is pretty exciting.
I was going to mention the venturi method of pulling a vacuum using an air compressor at 30-40 PSI to drive it, but I see someone has posted all the details. This is an excellent method of creating a very good mid-range vacuum for experimental purposes, although a bit noisy, LOL.

The 2nd comment was to wonder if there would be any value in having a soft rubber (or other soft, compressible, airtight material) gasket between the bottom of the two-part piece that holds the plastic to be formed, and the vacuum plate. Even stick-on weatherstripping might work, although getting a tight seal at the corners would require some careful work.

#3 - Would a couple or three "heat lamps" - 150 watt bulbs, I think, with built in reflectors and a reddish face - aimed at the top of the platen be of any use in keeping the plastic at a more flexible temperature during the actual forming process? The heat is diffused, but strong. They would allow full access to the piece being worked. I use one to pre-heat the cylinder head on my snowblower when it's -30, and it's very effective. (I think they sell these bulbs for use in bathroom/shower ceiling fixtures).

An alternate source of vacuum is an old refrigeration compressor. Not all compressors will work for this - I happen to have a couple of ancient ones in my shop..The simplest test (if you don't have a vacuum gauge) is to put your thumb over the intake pipe and switch on. These units will pull quite high vacuums - the disadvantage is that the volume of air moved is low. Be careful - if it is a "suck" type without a relief valve, you can get a blood blister very quickly. One option might be to start with the shop vac or venturi vacuum source to exhaust the majority of trapped air, then stop off that hose opening and start up the refrigeration unit, connected separately to your base-plate assembly, to pump it down further. This is probably beyond your requirements, but I mention it as I've used them as a vacuum source for other projects, with good success.

Loved this Instructable. I can see all sorts of possibilities - custom-forming covers for small home-brewed electronic or electro-mechanical devices, for instance. Thanks for sharing.
A P.S. I see the earlier poster added a link to a commercially available venturi vacuum source that connects to an air compressor. However, if you're cheap, or broke, a search of the online archives of a) Popular Mechanics b) Popular Science, and c) the British publication "Model Engineer" will
turn up several different articles on how it's done and what the critical dimensions are.

If you're searching "Model Engineer" index, you'll find a lot of info under articles on "Injectors" - used to force water finto the pressurized boiler of a steam locomotive, driven by steam. Boiler pressures can exceed 200 P.S.I., so the injectors can operate at far higher levels than you'd need for vacuum forming. However they have the advantage that they can be shop-built rather than purchased. I made one low-pressure experimental one, run on compressed air, using two disposable plastic cones from the instrument doctors use to look into patients' ears. Being a cone-within-a-cone venturi, and although normally used with water, they can be adapted for other things.
Thats a really cool form well done please post a pic of the final phone


Steve
Shanderson1 year ago
This is a great instructable. There are many things that I have had interest in doing, but was sorta stopped short when I didn't know how to do a custom vacuum form (like making a handheld 64).

Great work!
Thanks for this excellent I'ble! I'm going to build one.
Very Cool!

I know this adds cost to the set up but if willing to take the $85 plunge, adding a venturi with compressed air (might need a compressor as well, anywhere from free to $50) can get you up to 26" of Hg.

If not familiar, just hook up an air compressor to the venturi with around 30 psi continuous (very common pressure) and hook one end up to the vacuum plate. My buddy used to use this to create vac plates sometimes 12" x 18" large for vertical and horizontal CNC machining applications where huge cuts were being taken and the parts never moved (strong vacuum).

http://www1.mscdirect.com/cgi/NNSRIT2?PMAKA=80059710&PMPXNO=2125851&cm_re=ItemDetail-_-ResultListing-_-SearchResults
Nice Instructable! Simple and to the point.

I'm curious about where you source your plastics? I know you said you used excess that you already had. I've always had trouble getting plastic when I need it.

Just a couple of notes:
1) if you make the holes in your surface smaller you can get a more even and more detailed form. For example, if you halved the drill bit size, and doubled the number of holes (other than creating more work for yourself in drilling) the "resolution" of your form increases and the detail and continuity between formings gets better.

2) To get more detail in the forms you can drill small holed through your original model around detailed areas (for example in the holes of the rotary dial on your phone) these small holes give more suction in those areas and pull the plastic in firmer and into places where there might otherwise be bubbles, just be careful not to cause the model to get stuck in the plastic when it cools, or to make holes too deep and put holes in your plastic!
I've had good sucess cutting plastic from jugs. there are a lot of thicknesses, and colors available.
Eric Hart (author)  RandomIdeaMan1 year ago
Hi RandomIdeaMan,
Thanks for the tips. I'll have to try more/smaller holes on my next version. I did have some holes drilled throughout my model on the concave parts; I added a bunch more after my first test.

As far as buying plastics, I've always found Googling your local area for plastics fabrication/supply shops is useful. These places usually seem to be located off the beaten path and few of them have websites. But if there's one within a reasonable driving distance, the price is almost always cheaper than what yo can get online, particularly with shipping prices for large sheets.

Your big box home improvement stores will have acrylic sheets, and the "For Sale" and "Garage Sale" signs they have are usually styrene, which is a good plastic for vacuum forming. Craft stores like Hobby Lobby and Michaels usually don't have anything useful, but if you can find hobby/model airplane or train stores, they may have small sheets of styrene in a variety if thicknesses.

Sign-making shops may be willing to let you have off-cuts of vinyl and other plastics they use, or may let you know where they get their plastic from.
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