vacuum pot

[Renéduret]

Dear all,

the home caster I am, sometimes found some difficulties when casting little parts, like heads.

the appear to have little airbubbles and professional casters always use vacuum installations.
Some things are written about it, creating the vacuum constantly by use of mechanic compression ( vacuum hoses sometimes are used for this but give to little power)

Also a lot of work to create such an intallation.

The wine lover in me got this idea to create a vacuum pot and make the vacuum constantly, creating the vacuum with a well known wine preserver.

to keep it tight, I folded some double sided tape around the pot.

when closed in tightly, it works!

I hope this will get the bubbles out of my casts in the end.
just wanted to share with you...

usually the provider of this little vacuum pomp normally also delivers food boxes for the same idea.

René

 

[gordy]

Ingenious

Is there any kind of seal around the plane and the pot ?

 

[Renéduret]

yes Gordy..

I used dubble sided tape for this moment.
wrapped around the outline of the pot.

still not 100% closure, I hear a hiss sometimes.

this manufactorer provides this:

http://www.vacuvin.com/Vacuum_Coffee_Saver_500_g_286_356_920.html

I think the vacuum must work the first minute.
This way you can varify the balance between harder and resin.

René

 

[ookami]

interesting solution.

 

[megroot]

Rene,
I believe that into the vacuumpot the results are better then creating it yourself.
At the link you given us, there you have what you made.
And believe me that is vacuum....because i have one at home.

Marc

 

[Renéduret]

I just fixed the 'hiss' and must say this is also a nice vacuum marc, the upper plate is still bended to the inside.
I even mounted the vacuumhose on it few minutes ago just to test his power compared to the pomp.

these special boxes for coffee are perfect, but sometimes malls are larger than that.

 

[pokrad]

Rene, You should just simply put some rubber on the plane (still can leave a good sized window to see through), and when vaccum presses the plane against the pot there will be a good seal.
But crucial thing is still vacuum pump, it has to be strong enough to break the bubbles on the surface of the silicone. My try with Vacsy failed miserably, and ended up using much stronger pump for that.
Also be careful, that glass plane might even break, I suggest to put something stronger (and not glass) for that.
My current "setup" is far from perfect, but is "strong" enough to make a bit more than -0.9bar, and bubbles are popping like crazy when degassing
I also find out that releasing vacuum for two-three times during degassing also helps to break the bubbles on the surface.
Also have in mind that silicone have this property of "volume expanding" during degassing, it will raise up (about 4 times increasing the volume) and then when most of the air is out will drop down again...so You must have enough space in the "mold holder" to avoid leak out...

 

[Renéduret]

my God Darko,

you're a specialist ;-)

I used no glass, its acetate plate that looks like glas.

just sorted some things out this afternoon that were available in my home.

good tips!

 

[gordy]

Plexiglass is perfect for the plane, with a rubber sheet cut to fit for a seal.

Darko, is correct, the mold box needs 2 times the height to catch the boiling resin.

 

[mil-mart]

Rene, would love to know if this works, have you done any samples we can look at.

Cheers Ken

 

[pokrad]

Far from specialist, but man has to learn from his failed attempts, and I had more than a few
In fact I spent almost 1 Kg of the rubber on the failed attempts !
There is an old saying here: "Svaka škola nešto košta", or to translate,
"every knowledge has it's price", so I do not think of this spoiled rubber as a waist, but as material spent in learning process...

I forgot to mention, I also put some rubber into deep recessions and make one thin layer of the rubber across whole original with the brush before pouring the rubber. It helps also to avoid air bubbles in the critical places

One day I hope will get something more "professional" for degassing, but until then...

 

[gordy]

I forgot to mention, I also put some rubber into deep recessions and make one thin layer of the rubber across whole original with the brush before pouring the rubber. It helps also to avoid air bubbles in the critical places

Degassing the rubber and original also helps

 

[Renéduret]

I am trying now Ken.

Even opened a 'fresh' bottle of resin and harder.

in the 'old' bottles sometimes the resin already poors out white, new ones is more fluent.

 

[pokrad]

Gordy, I am not degassing the rubber itself (before pouring) at all, find out that if I pour if thin enough stream, it almost has no difference.
So I only brush the original, pour the rubber and degass together.

Now when we are talking about "garage methods" of making molds in general, I want to hijack this thread and show something that frustrated me (hope Rene would not have nothing against).

I spent so much time on making "mold holder", and every piece has to have it's own sized pot.
Then this idea comes into my mind, make a "reusable variable size mold holder-mold pot".
I used it for a few times now, and can be used again. Here is how the thing looks "assembled":

it contains 4 identical planes:

I put some clay around to avoid the leaks, but if the clamps are strong enough, and the planes made precise enough, that would not be necessary.
Now I adjust size, put some clay around and it is ready if 5 mins

Regards !

 

[1969]

Another great method for making mould boxes is Lego bricks, you can make any size box you require and use the bricks over and over again.

Steve

 

[Renéduret]

all the info on casting is welcome here Darko, I am glad you share.

your method is a very good one, especially when you fill up with clay.
It saves a lot of rubber...especially when one is aquinted with weighing silicon and harder by digital scale ( which I'm not)

I always work with lego parts.
Both your wall as a lego wall can easily be teared down.

I like reading about it.

no hi jackin, no no...

René

 

[Renéduret]

Ken,

I just had to try today but I personally don't have more benefits from the vacuum pot.

a lot of bubbles actually seemed to be coming up compared to using none.

the little airbells frustrated me in the little heads and got back to old school :-(

pooring out resin, poking a bit with needle to eliminate the worst inclusions..

...and just wait...

this is as good as it gets at my home station:

what doesn't mean I won't investigate the use of the pot with best circumstances


René

 

[jasmils]

G'day All,
This is my set up.
I have found thou my casting time, that Vacuum will not get rid of all the bubbles in either resin or rubber. But vac will minimise the amount of bubbles when making the rubber mould. When it comes to resin, the trick is to not let the resin "cold boil" in the vac chamber, as this can create even more bubbles. The use the vac first to coat the inside of the mould with resin and then I top up the reservoir and then place it in the pressure pot until it goes off. I can get some amazingly thin and complex parts this way and with bugger all of a sprue.

Cheers Jason

 

[Renéduret]

Hi Jason,

This really looks good!

Using the vacuumpot when making the rubber mal is something I will do next time.
It takes longer to harden and air bubbles have a lot of time to escape the mall, effective.

when preparing the mall with resin as you said, how do you apply it?
Is there also some kind of liquid that enhances adhesion of resin?
I also use chalk ( talk) powder that I firmly blow away at the end before pooring.



thanks!

René

 

[pokrad]

Hmmm, Rene I am wondering if here would help Polyester resin, such as that first cast of mine was. It cures for 24h and have pot-life more than 60min, so there is plenty of time to vacuum. I did not have a single bubble in that first cast, and it was vacuumed for about 10 min. Sure there is problem how to avoid its transparency, but it might be a solution that we can afford for such small pieces ?
Soon I'll have the same problem as M-48 that I'm preparing has plenty of tiny bits hard to cast-I'll let you know if this works

Regards !