vacuum chamber..

[mickc22]

anyone got any info on how to make one?
I\'ve got a compressor already for my nail gun, would that be too much for use as a vacuum pump

I\'ve just been watching some You Tube vids of a guy calledRomaurie, using fridge compressors (he was making strange aquariums tho) so they seemed strong enough
I have played around with fridge compressors years ago, but not for pulling a vacuum
I just can\'t justify buying a dedicated machine for the small amount of mold making and casting I\'m doing at present

any tips, links, pointers are much appreciated

 

[BarstoolProphet]

You could just use a fireplace bellows, if you reversed the valve at the back so that it pointed inward, instead. Or is that too simple?

Beyond that, it\'s all over my head.

 

[Bigdennis52]

I was thinking of something along those same lines. How about taking a air bed pump and reversing the gears to go inward... just a thought

 

[Shawn R. L.]

Not sure what kind of material you will be vaccuming but if it\'s resin, it\'s important to be able to drop the pressure fairly fast since it set\'s up so fast.

 

[Dragon Forge Design]

Mick, are you saying you want to draw a vacuum or do you want to pressure cast? Two different things here. An air compressor wont draw a vacuum to remove air but will apply pressure to pressure cast.

I use a dedicated Vacuum pump to degas all my mixed rubber before pouring and sometimes after and I use an air compressor along with paint pressure pots converted to pressure cast my resin.

To degas RTV silicon you need a pump that will pull at least 26Hg or you wont degas properly.

As I only work with fast setting resins Ive never degassed resin.

What are you attempting to do?

As for my Vacuum chamber, I use a very large Piece of PVC pipe 12\" in inside dia which is 1/2\"-3/4 wall thickness with a top and bottom l3/4 inch lexan sheet with silicone gaskets and some brass hardware with a vacuum gauge attached.

 

[Bigdennis52]

Originally posted by Dragon Forge Design

As for my Vacuum chamber, I use a very large Piece of PVC pipe 12\" in inside dia which is 1/2\"-3/4 wall thickness with a top and bottom l3/4 inch lexan sheet with silicone gaskets and some brass hardware with a vacuum gauge attached.

Any way you can put a picture of that up so I can figure out how to build it?

 

[mickc22]

Originally posted by Dragon Forge Design
Mick, are you saying you want to draw a vacuum or do you want to pressure cast? Two different things here. An air compressor wont draw a vacuum to remove air but will apply pressure to pressure cast.

I use a dedicated Vacuum pump to degas all my mixed rubber before pouring and sometimes after and I use an air compressor along with paint pressure pots converted to pressure cast my resin.

To degas RTV silicon you need a pump that will pull at least 26Hg or you wont degas properly.

As I only work with fast setting resins Ive never degassed resin.

What are you attempting to do?

As for my Vacuum chamber, I use a very large Piece of PVC pipe 12\" in inside dia which is 1/2\"-3/4 wall thickness with a top and bottom l3/4 inch lexan sheet with silicone gaskets and some brass hardware with a vacuum gauge attached.

yeah, to degass the RTV

I\'ve seen some info on pressure casting, how does that work then?

Ah! I just might be able to get hold of some pipe like that, they are laying new water mains not far from me, I\'m sure they\'d have an off cut long enough

 

[Einion]

I don\'t know if this only works with resin but I have a friend in Switzerland who says you can get decent degassing with a domestic vacuum cleaner, shoving the hose end into a hole cut in the side of a plastic food container.

Einion

 

[freakinacage]

Originally posted by Bigdennis52
I was thinking of something along those same lines. How about taking a air bed pump and reversing the gears to go inward... just a thought

some even have a reverse valve included so you just swap em over

 

[nels0nmac]

The difference between a vacuum chamber and a pressure pot is this. The vacuum chamber lowers the pressure inside and causes any gas in the mold / resin to bubble to the surface hopefully resulting in a final finish with no holes/bubbles in it. Vacuum chambers work well for larger more simple molds.

The pressure pot builds up pressure and causes any bubbles in the resin/silicone to be compressed to the point where they are no longer visable. pressure pots are more useful for fine complex molds as any places where air is likely to get trapped don\'t matter as much as the air is compressed and the resin fills its place.

The pressure pot that I have used produces perfect molds and casts. However it does need to pumped up to 60PSI / 4Bar.
It would be inadvisable to try and make one yourself unless you have engineering skills as it could get painfully messy.

 

[Dragon Forge Design]

Originally posted by Bigdennis52

Originally posted by Dragon Forge Design

As for my Vacuum chamber, I use a very large Piece of PVC pipe 12\" in inside dia which is 1/2\"-3/4 wall thickness with a top and bottom l3/4 inch lexan sheet with silicone gaskets and some brass hardware with a vacuum gauge attached.

Any way you can put a picture of that up so I can figure out how to build it?

Looks a lot like this

http://www.alumilite.com/ProdDetail.cfm?Category=Equipment&Name=Vacuum%20Chamber

I just made my own.

 

[Dragon Forge Design]

Originally posted by mickc22

Originally posted by Dragon Forge Design
Mick, are you saying you want to draw a vacuum or do you want to pressure cast? Two different things here. An air compressor wont draw a vacuum to remove air but will apply pressure to pressure cast.

I use a dedicated Vacuum pump to degas all my mixed rubber before pouring and sometimes after and I use an air compressor along with paint pressure pots converted to pressure cast my resin.

To degas RTV silicon you need a pump that will pull at least 26Hg or you wont degas properly.

As I only work with fast setting resins Ive never degassed resin.

What are you attempting to do?

As for my Vacuum chamber, I use a very large Piece of PVC pipe 12\" in inside dia which is 1/2\"-3/4 wall thickness with a top and bottom l3/4 inch lexan sheet with silicone gaskets and some brass hardware with a vacuum gauge attached.

yeah, to degass the RTV

I\'ve seen some info on pressure casting, how does that work then?

Ah! I just might be able to get hold of some pipe like that, they are laying new water mains not far from me, I\'m sure they\'d have an off cut long enough

Well it need to be rather thick walled and the ends need to be perfectly squared off. What I used was actually a very large coupler made for PVC sewer pipe.

 

[mickc22]

Originally posted by nels0nmac
The difference between a vacuum chamber and a pressure pot is this. The vacuum chamber lowers the pressure inside and causes any gas in the mold / resin to bubble to the surface hopefully resulting in a final finish with no holes/bubbles in it. Vacuum chambers work well for larger more simple molds.

The pressure pot builds up pressure and causes any bubbles in the resin/silicone to be compressed to the point where they are no longer visable. pressure pots are more useful for fine complex molds as any places where air is likely to get trapped don\'t matter as much as the air is compressed and the resin fills its place.

The pressure pot that I have used produces perfect molds and casts. However it does need to pumped up to 60PSI / 4Bar.
It would be inadvisable to try and make one yourself unless you have engineering skills as it could get painfully messy.

thanks for that, no I\'m not gonna make a pressure pot, I\'ve seen/heard a couple of pressure cookers go off to leave that alone.
That\'s one thing I would buy

Thanks DFD, that pretty much ties in with what I had in my head

I\'ve also just joined the casting group on yahoo, should be plenty of info there

 

[airhead]

Originally posted by mickc22
...thanks for that, no I\'m not gonna make a pressure pot, I\'ve seen/heard a couple of pressure cookers go off to leave that alone.
That\'s one thing I would buy

Thanks DFD, that pretty much ties in with what I had in my head

I\'ve also just joined the casting group on yahoo, should be plenty of info there

An imploding glass jar will make the same mess as an exploding one and stick the glass in the walls just as deep. Trust me.

 

[mickc22]

thanks for the heads up Kev, I\'ll avoid the use of glass then

 

[mickc22]

you\'d think finding a pressure gauge would be a cheap and simple matter

If I lived in USA I could get one in a local shop for under $10

not here, I can\'t, gotta do a special order, from a specialist company, £10 for the gauge + £12 P+P

the only ones I could find on ebay are for car dashboards
GRRrrr...rr..rr...r!

 

[Bigdennis52]

Originally posted by mickc22
you\'d think finding a pressure gauge would be a cheap and simple matter

If I lived in USA I could get one in a local shop for under $10

not here, I can\'t, gotta do a special order, from a specialist company, £10 for the gauge + £12 P+P

the only ones I could find on ebay are for car dashboards
GRRrrr...rr..rr...r!

I love the USA
lol

 

[moonmin82]

where i work we use a fair bit of resin and some guy threw a mini vacuum chamber together that does the trick:

its basically a generic pot that you put your resin piece in. on top of this theres a lid with a hose attached. the hose is attached at a right angle to a hose attached to a tap.

the flow of the water draws air in from the tube and when you create a seal on the lid a use-able vacuum is created.

i may be slightly drunk and eating a giant quiche, but it works!! :drunk: