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ant...
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Buying a decent size vacuum chamber costs upwards of £1000 but all we really need is some plastic tubing, thick plastic sheet to cap the ends, pvc hose and silicone. The problem has always been how to get an airtight seal at the opening, well I found some airtight foam strips/sticky backed that were being sold to carpenters to hold down work with a vacuum, but the product was expensive and cut into thin strips Vacuum Workholding Product. So I trawled the suppliers database and found out the raw material was made in a town bordering my own. Munsch & Co make all types of airtight foams and they can sell you a sheet as large as you need at a very cheap price. Ive got a 30cm x 30cm square metal baseboard, covered in airtight foam, with a hole drilled in the middle which is connected to a vacuum pump that id bought from carbon mods. If i place any jar over the middle and turn the vacuum pump on the pressure pulls the jar into the foam creating an airtight seal. The beauty of this system is you can change the size of belljar to suit your job, a coffee jar is good for degassing and I use a big clear plastic tube for larger jobs. Pics coming soon...
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Matthieu Libeert
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Great thinking 
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Wabba
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Slightly off-topic but what is a vacuum chamber used for?
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neilb
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i modified an aluminium pressure cooker to vacuum the resin before i use it infuse, only problem is not being able to see in. might give your way a go or thinking about it maybe just remake the top with some thick clear plastic. thanks for the idea
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Joe
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Wabba (18/04/2012)
Slightly off-topic but what is a vacuum chamber used for? Hi, A vacuum chamber is used to degas materials, would it be resins or silicone or whatever. Degassing stuff before proceeding on making your part reduces the risk to have air bubbles appear in your final part.
 A $1000 electronic device will always protect a 10 cents fuse
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ant...
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As you can see from the size of my vacuum chamber, I use it for allot more than degassing. Its great for getting bubbles/voids out of wet layup and it can be used for resin injection too. The black foam that you can see on the basseboard is so good it produced a 30 mercury reading (could be due to the pressure meter). If I were better at sealing vacuum backs then I wouldnt need this unit so much  Neilb - I did the pressure cooker first and got the same problem, I also found it didnt give a consistant vacuum. After that I built a box with a pair of space men arms that could work inside, that was a massive failure, mainly cos at presures over 15 mercury you couldnt move the gloves LOL As promised here is the pic...
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Mr Rooty Tooty
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I bought a thick walled aluminium cooking pot from Ikea ages back and I modified that. It had two handles on the side with holes drilled through and pop rivetted. I just ground the rivets off, filled the holes and around the outside of the holes with epoxy and put some rectangles of thin metal over to cover. To make the top I just bought some thick (2 inch or so) perspex, fitted a nipple for the vac pump and fitted a small gauge. I sealed the perspex against the pan using some gum tape. You can pull pretty much as much vacuum as you like, never had any issues. Plenty of space inside and total cost was less than a tenner! (Mind you, I already had the pan ) I did look at getting bell jars but they cost a fortune!
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ant...
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^ Perspex top - thats what made yours work better. I tried using the lid, I bought 2 lots of rubber seal, used silicone but never got it to work 
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Mr Rooty Tooty
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That gum makes a decent job of sealing absolutely anything.... ...seperating it afterwards, that's the trick The perspex was easy because it was a flat surface mating a thin wall. I just put some cooking oil over one side so that it didn't stick too much and could be seperated and resued easily. Worked fine but was a bit messy and a bit low tech if you were doing high turnaround. I stopped bothering degassing resin because it didn't seem to make a huge improvement on finish. I think resin infusion was the process I was waiting for back then!
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ant...
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Group: Forum Members
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im still having problems with infusing/voids. IMO the process for a great finish is: first remove air, then infuse resin (prepreg = apply heat, infusion, vac chamber = inject resin) Ive done lots of testing on how to get rid of air bubbles and voids with wet layup by applying cf inside clear jam jars and vacuum bagging, I found their was no process that could remove the air bubbles, not manipulation, vacuum or heat.
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