The term “vacuum” means many different things depending whether you are working on space equipment, scientific instruments, or even internal combustion engines. In our sphere it is so often used as a means to draw bubbles out of resin castings, for which it is a relatively easily achievable partial vacuum. It’s something [Fab] is using, in a vacuum chamber made from Plexiglass.
A simple Plexiglass box would collapse under the air pressure on its own, so to mitigate that it’s made from a piece of tube, and with an internal frame of aluminium extrusion with 3D printed joints to strengthen it from the inside. A pressure sensor allows regulation of the pump that drives the vacuum, and connections are made to the chamber using pneumatic hose connectors. It’s not immediately clear how it is sealed, whether there are nay gaskets or other sealant, or whether air pressure pushing the parts together provides enough of a seal.
We’ve featured a lot of vacuum chambers made for this purpose over the years, and we’d be interested to know what vacuum pump is being used here. If you’re curious too and want to build your own, perhaps you could try a fridge compressor.
31 thoughts on “An Affordable Home Made Vacuum Chamber”
It looks kinda like transparent pressure cooker bomb.
Maybe if you added a homemade clock to it?
Just don’t bring it to school…
For impregnating a magneto coil I once made a very inexpensive setup using a sandwich container and a 12V tyre inflator.
5th photo down here: http://bodgesoc.blogspot.com/2014/06/neracar4.html
It worked well enough for a one-off job and took about 10 minutes to cobble together.
More hackier than the one in the article, so better, right :-)
Yeah, that goes in the same direction like my first try. :D Didnt work. At least not with the box i had… Video. https://www.instagram.com/p/B-uajpuqyhk/
Looks kind of overengineered to me. Happens to all of us, sometimes. Did this on a weekend with spare IQS mini connectors, PTFE tubing (think 3d printer bowden extruder spares), a plastic food storage box with silicone seal in the lid and a 12v vacuum pump pulled from a food vacuum sealer. This trash setup proved sufficient to degass small amounts of addition-curing silicone (~40ml) before curing started (after 9 minutes). After this first success I added a vacuumeter. Looks like that setup can pull around 0.4 Bar, pump has to be run two times during curing to keep the vacuum. To be honest, I was kinda surprised that setup from stuff lying around worked quite so well.
Made from plexiglass?
I would not settle for less then stainless cookingware pot with a polycabonate top.
If you want to mess around with plexiglass, then at least have the sense to wrap some canvas cloth around it, or put some plywood (mdf) between you and the pot. In that case, when it shatters the cloth or wood will hopefully keep the pieces together, or at least absorb most of the energy from the flying pieces.
For small chambers, 2 or 3 liter pop bottles with an end cut off make decent implosion shields.
The pressure on the lid can be a ton. I’ve had good quality commercial chambers implode. It only takes a scratch to concentrate stress and have it implode. A clear chamber may look cool but a stainless steel pot is much safer and probably cheaper. They can crumple but won’t throw plastic shards. For a hundred bucks I’m not risking a face full of plastic shrapnel.
This one looks too fragile. The lid on my small chamber is an inch thick. And, full face shield is absolutely required.
The force on the lid can be anything, it depends only on the size and doesn’t _really_ depend on the quality of the vacuum. (the difference in net force between a moderate vacuum (say 0.1 atm) and a theoretical perfect vacuum is only 10%. This is something I have had to explain a number of times while working briefly in vacuum system design. If you make the vacuum twice as good you don’t double the force)
The force is one tonne for a circular lid 350mm / 14″ dia (approx)
But then a ton isn’t all that much force. There is a lot to be said for a transparent vacuum chamber, but there is also a good argument for keeping it in a cage.
Also have to remember that across the lid the force is distributed so the actual forces on your lid are not really 1T pulling down dead centre on a pin head. The whole surface is being deformed and the forces spread into tensioning the material of the lid. That said fair better to spec as if you needed to hold the full force at the radius length leverage on a small beam of your chosen material => over spec so it won’t fail!!
I’d never use such flimsy shatterable materials as done here, If you are going put something under so much stress you want it deform plasticly when it fails not shatter (or at least be a composite material so there’s something trying to hold the shards in). Otherwise it has to be so very much tougher than it needs to be that it can’t fail without extra help, and that means thick enough its going to cost a fortune..
Big fan of a transparent lid on a metal box – the metal can be nice and thin and the point that will fail first so it deforms first and takes some of the energy out which stops the plastic/glass lids getting even close to its breaking point. Also if you are going to use plastics use Polycarbonate!!! Its really good for this sort of job!
Move to Denver CO, not only do you get nearly a 3 psi head start, it’s also 20% less dangerous :-D
Though you’re reminding me there’s between 2 and 3 times the pressure differential in your car tires, I dunno if that says I need to be more fearful of car tires, or less fearful of vacuum chambers or what. Rubber doesn’t really cause shrapnel though. (Until you put a load of steel belts in it and give it a hundred PSI or so like truck tires)
I did consider mentioning car tyres in the context of 1 ton of force and air pressure, just to give a more intuitively comprehensible feel for things.
And, actually, I have been to Denver _specifically_ to have less air. (And got paid to drive up Pike’s Peak several times)
About 25 years ago I was at home in my living room and heard a loud explosion. I ran out to the front yard and my across-the-street neighbor was a bloody mess, especially his face. He’d been restoring an old tractor and didn’t know that the big tires ran at a *much* lower pressure than a car tire. He’d pumped it up way higher than it was rated at and the rim gave way showering him with shrapnel from his waist to his head. The good news is that he was wearing glasses, even though they were not real safety glasses, they protected his eyes. He was scarred badly after he healed, but he didn’t lose his eyes. Pressurized air is very dangerous. Of course, my wife was calling 911 as I ran across the street…
Ouch, exploding rims. Might be something to be aware of should one decide to run higher pressure commercial tires on a pickup or van that had passenger tires on.
Split rims AKA widowmaker:
Pressure vessel designer here. Could you elaborate on “and doesn’t _really_ depend on the quality of the vacuum”?
I mean that the difference between a moderate vacuum (say 10 torr) and a super-special-lab-grade-vacuum (10^-9 torr) is basically zero as far as the forces to be dealt with are concerned.
I see, by vacuum you mean something really close to full vacuum and not just underpressure as the term is usually used. Note that for the pressure bearing wall those 10% may still be significant if stability (shell buckling) is the governing failure mode.
The difference between 10 torr and 10^-11 torr is 1.3%. The point that I am making is that the external pressure is 1 atm. It doesn’t increase without limit the longer you keep pumping, but it is often assumed that it does. You can see this is comments on the original thread about this on Hackaday.io, with comments about not trying to pull a super-hard vacuum.
I long for a vacuum chamber with all my heart, and the only reason I haven’t bought one is that workshop space is also an issue, and they tend to be bigger than I would need. So I think a lot about making my own. But although I’d be fine risking my time and the cost of materials, I’m less enthusiastic about the risk of firing an acrylic shard through the center of my face.
The problem is, if you cut the plexiglas the wrong way or have a screw touching the wrong place, you won’t know about it until a microscopic crack forms and the whole thing shatters. So even if I were adapting a successful design, I wouldn’t be confident experimenting with something like this. I guess maybe I just need to do more reading about how to spec pressure vessels, until I feel like I can do it safely.
So use polycarbonate to entirely eliminate the risk of acrylic shards to the face. (And also to much reduce the risk of any shards)
The way to be safer is to have a “helmet” for it made out of 1/4 or 1/8 mesh hardware cloth. Cylinder of it with a plate sewn onto the end. Not a tight fit though, gapped a little. If you like you can ground it for a faraday cage also. Before you start to draw vacuum, put it’s hat on. Make it loose enough to get any cameras you want inside.
How big do you need? I have a pressure/vacuum chamber I built in an old pressurecooker pot.
Use the pressure pot lid with a tiny modification (remove its weighted cooking relief valves and add airline fitting – so you can feed air pressure in). But make sure to still have the overpressure prevention valve in there somewhere!
And a nice thick sheet of Polycarbonate with some fittings and a silicon gasket in place of the normal lid to pull the vacuum in the pan.
It works pretty damn well and takes up no more space than the pan on its own – as the polycarb sheet stays on top of the pan with the lid on top of that (pressure cooker lids are usually quite deep so the fittings are all covered over) – so all it gains is the thickness of the polycarb sheet and the airline fittings in height. Do of course need the pumps as well – but a vacuum pump doesn’t need to be large to evacuate a small pan to a reasonably low level effectively.
Its a little leaky in both directions but very functional and more importantly for me cost only for a sheet of Polycarbonate.
Go to Pier 1 or Hobby Lobby and get one of those glass circular flower vases of 10″ diameter or less.
Those things are really thick glass which does not break easily, and the bottoms are thick glass that won’t break at all.
Use an old microwave oven plate for the top. These are tempered glass that hold up to almost any amount of abuse. You can drill a hole through one easily enough with a cheap diamond drill from eBay, or spin a piece of brass pipe over some wet grit.
Get a “bulkhead union” plastic quick fitting for the hole and use PVC tubing from Home Depot.
Throw a towel over it to satisfy the nannys at HAD if you’re afraid of it, but it won’t implode without taking a hammer to it. And with a hammer it might take a couple of tries.
(I’ve used such a system to get town to milliTorr pressures many times – works like a charm.)
This sounds great, any pics?
Sorry – none.
I just checked my project directory, I’ve got the various design files but didn’t bother taking any pictures.
I made my vacuum chamber out of an old Tefal frying pan with round glass lid. Even though it seems to hold up fine, I keep it inside a transparent plastic box to contain shards if it would fracture.
Or you could just throw a towel over it
Thank you for your feedback on my vacuum chamber. :)
A few points to explain:
To the “The vacuum chamber implodes and destroys all life within a radius of 10 meters” problem:
I am not really trying to create the greatest vacuum / lowest pressure ever created with the chamber. My pragmatic goal is simply to pull out a few bubbles of epoxy. :D It is probably (I was told) important that the vacuum should not be too large. See comment here: (https://www.instagram.com/p/B-uajpuqyhk/comments/) “… just don’t pull too hard a vacuum as some of the lower molecular weight curing agents could evaporate off as well making for less effective cure … “. Additionaly the (actual) seal is simply not tight enough for large pressure differences. The lowest pressure I have been able to reach so far has been 800hPa.
Yes, the design of this box could actually be over-engineered. The first attempt unfortunately failed due to the weak can (Video: https://www.instagram.com/p/B-uajpuqyhk/) Therefore I thought “this time I’m going to be on the safe side” and built everything a little more solid. :)
Interesting, although the outgassing of most plastics under vacuum is severe.
For a trailing-edge solution, some amateur rocketry enthusiasts mix propellant (see “ammonium perchlorate composite propellant”, APCP) with a planetary-type mixer such as a KitchenAid. Bubbles are removed using the mixing bowl itself as vacuum chamber. Vacuum needed for such work is quite modest, around 10 mmHg pressure is adequate. The bowl is topped with thick polycarbonate sheet and a gasket cut from sheet rubber. Holes are drilled and tapped in the lid for ordinary plumbing fittings such as ball valves.
For mixing under vacuum, see http://www.novalab.org/rockets/mixer.htm for an enclosure made of high-quality 3/4″ plywood (gluing sheets of plywood together for double the thickness wouldn’t be a bad idea). A small polycarbonate window allows viewing during the process.
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