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.
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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Signing UpStep 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.
* 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.
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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...
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.
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.
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
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.
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 -
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.
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!
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
I'd be up for experimenting with ABS parts that have ice-filled cavities, to keep the abs object cool.
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.
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.
Steve
Great work!
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
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!
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.