Anyone know how to set up a small degassing chamber!

sskunky · Nov 16, 2009

HI,
as the title suggests. Does anyone know how I can set up a cheap small degassing chamber for small silicone molds without having to spend hundreds of pounds on a commercial one?
I think I need a small pressure bucket, pot or tube with a pressure gauge, a window of some sort maybe an acrylic see-through lid and a vacuum pump of some description. I'm not sure what Vacuum pump I would need? I would like to run it on the mains electric.
Basically a degassing chamber on the cheap.
Any help would be great......

sskunky · Nov 17, 2009

Has no one ever built one? I would have thought you would all be throwing advice at me.
Well if I get one together maybe I should do a build thread.

Adam H · Nov 17, 2009

I'd also be curious to know how to set up one of those on the cheap. I'll look up regular ones when I get home from work and see if I can come up with anything.

sskunky · Nov 17, 2009

Hi Adam,

I have done quite a lot of research about these in the last day or two and the hardest thing to find is a large enough diameter PVC tube to use without having to buy 6 meters of the stuff. Even then I haven't found anything in the region of 10" or 12" diameter. A pipe coupler is supposed to be good enough for the job but again I am finding it hard to find anything the right diameter. Pumps are easy to come by and apparently anything that pulls over 4cfm will be sufficient. The lid can be made out of polycarbonate 1/2 inch thick or there abouts. I have found some that can be cut to size and is 12mm thick that should be OK. fitting I'm sure can be found easily but getting the correct name of them to do a search is hard for me. I know I need a ball valve or two and a couple of male hex nipples etc.....
I found this set up that looks fairly easy and cheap. It's just finding the tube that's holing me back. This is using a steel pot so maybe a pressure pot of some kind could be used.

sskunky · Nov 17, 2009

This is more of what I was thinking about though......

And this which is home made:

JPolacchi · Nov 17, 2009

Sometime back I recall someone I the rpf having one built(all welded steel).You need something that can withstand the 29HG vacuum.It must be pressure tested or it will either not work,or you will have a major catastrophe.I also know(at one time) Tap Plastics was selling a small one somewhere in the vacinity of $400.00.It came with a vaccume pump and pressure vessel with an airtight closing/locking lid.It was good for degassing small molds/castings.

cheech9898 · Nov 17, 2009

Do a forum search. I know I've posted an eBay id to a company that sells large diameter PVC pipe in the past. Another option is contact your local water dept and inquire about short scraps (or do the same with a subdivision developer)

sskunky · Nov 18, 2009

cheech9898 said:
Do a forum search. I know I've posted an eBay id to a company that sells large diameter PVC pipe in the past. Another option is contact your local water dept and inquire about short scraps (or do the same with a subdivision developer)

Hi,
Thanks, I have seen the Tap vacuum set up it's $695 which is still a good price for a complete set up but I am in the UK and shipping would be a killer.

Uncannily I went round looking for works replacing pipework yesterday and fond some pipe but it's only 7-8 inches, not quite big enough. I will try and contact the water works to see if they can help.

Fireball Joe · Nov 18, 2009

sskunky said:
Hi,
Thanks, I have seen the Tap vacuum set up it's $695 which is still a good price for a complete set up but I am in the UK and shipping would be a killer.

Uncannily I went round looking for works replacing pipework yesterday and fond some pipe but it's only 7-8 inches, not quite big enough. I will try and contact the water works to see if they can help.

I made my vacuum chamber from a short length of water main pipe that I "liberated" from a roadside work site (it was in a scrap pile left over after the work was completed). My lid is a piece of 1/2" polycarbonate. The base is also 1/2" polycarbonate. I glued the pipe to the base with silicone adhesive and the top gasket is made from RTV rubber. I tapped a hole in the side of the pipe for standard 1/4" air fittings and installed a 4-way brass cross-coupler with a ball valve, a gauge, and a barb connector for the air line. The air line is 3/8" ID reinforced tube. I use a 3cfm single-stage vacuum pump with the chamber and it draws down very quickly. It's boiling rubber in about 15-20 seconds.

My Sources:
Water Pipe for chamber: roadside
1/2" Polycarbonate: Ebay
Vacuum Pump: Ebay
Vacuum Gauge: Ebay
Brass Fittings: Harbor Freight Tools & Home Depot
Air Tubing: Home Depot

Of course, I had to use some special tools to assemble the chamber. I used a 12" cut-off saw to cut the water pipe (that was a little scary!) and drill press and a 1/4" NPT tap to make the hole in the side of the pipe. Overall, I spent about $50 on the chamber itself and the vac pump was another $100. It's expensive, but absolutely necessary for the casting work that I do.

sskunky · Nov 18, 2009

That's exactly what I'm talking about. Great little set up. I'm actually thinking of using a large capcity pressure cooker pot as the main pot and a poly lid like yours.
I think that will work. I can either drill into the side of the pot as you did or attach it to the lid as in the picture above.

Fireball Joe · Nov 18, 2009

sskunky said:
That's exactly what I'm talking about. Great little set up. I'm actually thinking of using a large capcity pressure cooker pot as the main pot and a poly lid like yours.
I think that will work. I can either drill into the side of the pot as you did or attach it to the lid as in the picture above.

You don't even necessarily have to use a pressure cooker pot; you can use a good-quality stock pot instead. There's a guy on Ebay over here that sells a vacuum chamber & pump combo that is made with an aluminum stock pot. I'd recommend not trying to drill the metal pot but instead plumb through the lexan lid. A hole in the lexan is a potential weak point, but as long as it's thick enough to handle the span across the pot without too much deflection under vacuum it should be fine for a long time. I searched around for a while for a suitable piece of pipe to use for my chamber; had I known that the stock pots were strong enough to use, I would have made a vacuum chamber much sooner than I did!

Joseph

sskunky · Nov 24, 2009

the top gasket is made from RTV rubber.

How did you make and attach this gasket?

racecardriver03 · Nov 24, 2009

EDIT... sorry i can't list an auction in the forum.. newbie here. I was selling one I built on ebay.

Here's my personal one. Hopefully this provides some insight.

Here's my original version. I used an old pressure pot, some lexan, some 1/4" piping. It took a bit of work, and some learning.. considering I didn't know anything about plumbing prior to this project.

Man that's ugly.. But it works. I've since learned how to construct it a little better and make it look purty.

Here's a more updated version

%21Be1OkDg%21mk%7E$%28KGrHqQH-DIErdzeYJD6BK-15%28lTp%21%7E%7E_12.JPG

sskunky · Nov 25, 2009

That'll work. In fact for that price I'd be all over it if I didn't live in the UK. Shipping would be a killer. I don't think links to eBay are a problem if it's your own auction.

Monkeywiz · Nov 25, 2009

Love to know where you get materials from and your contruction method when you get this sorted out SS.

sskunky · Nov 25, 2009

Monkeywiz said:
Love to know where you get materials from and your contruction method when you get this sorted out SS.

The cheapest place to get lexan ploycarbonate 12mm or 1/2" sheet for the see through lid is eBay I have found. The same for a vacuum guage and some of the fittings too. I found some pipe on the side of the road but it's only 7" in diameter but will do until I get something bigger. I think it was a gas pipe, the yellow stuff. I just asked the workman for a spare off cut.
I have just ordered a vacuum plate off the net to see if that works. It's £49+vat and delivery. If it works I won't need the fittings or a guage, just a gasket for the lid as the plate comes with it's own gasket. I've been thinking that degassing silicone is a visual thing so it doesn't need to a precise bit of laboratory kit. As long as I get a good seal and get 29Hg that will do. I may add a guage etc at a later date but I want this to be a budget degassing chamber.

tomstrong · Nov 25, 2009

Would a piece of glass work for a top plate if it's thick enough? (1/2" if not more) I know that Polycarbonate is much more shatter-resistant, but if the plate is strong enough is that a concern? (The thick plastic is expensive, but I have a possible source for cut-offs from glass tabletops that is much cheaper)

sskunky · Nov 26, 2009

tomstrong said:
Would a piece of glass work for a top plate if it's thick enough? (1/2" if not more) I know that Polycarbonate is much more shatter-resistant, but if the plate is strong enough is that a concern? (The thick plastic is expensive, but I have a possible source for cut-offs from glass tabletops that is much cheaper)

I would think so as long as it's tuffened/tempered and thick enough

racecardriver03 · Nov 26, 2009

tomstrong said:
Would a piece of glass work for a top plate if it's thick enough? (1/2" if not more) I know that Polycarbonate is much more shatter-resistant, but if the plate is strong enough is that a concern? (The thick plastic is expensive, but I have a possible source for cut-offs from glass tabletops that is much cheaper)

sskunky said:
I would think so as long as it's tuffened/tempered and thick enough

DO NOT USE GLASS. Use polycarbonate only! Glass will shatter. 1/2" thick or not. Seriously though, when was the last time you saw a 1/2" piece of actual glass. Chances are anything that thick.. is probably polycarbonate. Seriously, you probably wouldn't even save yourself that much money. Plus you really can't tap glass like you can carbonate.

I've cut glass fish tanks before with a diamond hole say to add plumbing. You can't tap the actual glass for threads. They have something called a bulkhead which works sort of like a union. It just tightens up against the glass. You'd never be able to take any type of tap and put threads in glass... well maybe you could, but you'd be bound to break them. I guess you could put your fitting on whatever your using for a tank, but.. seriously, I don't want to hear about anyone getting hurt from shards of glass getting sucked in a vacuum chamber and then bouncing back their face.

sskunky · Nov 26, 2009

Correct me if I'm wrong but old vacuum chambers/bell jars used to be made of glass and a simple rubber bung was used for the conections of the tubes etc. I take it that it was the bell shape and not a flat piece of glass that made it safe?

Anyone know how to set up a small degassing chamber!

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