Vacuum chambers

[AndriesH]

PH wrote:

AndriesH wrote:

Time is your other factor.
If you need a fast vacuum time, connect your compressor to a "storage" cylinder, like a vented 48kg LPG or similar via a T piece and let it run for a while.
Once the vacuum is drawn in the cylinder, connect to your product chamber and open the inline valve, and whooosh - emptiness.

A few thoughts on this: would this really be efficient? I think you would only equalise the pressure between the two tanks. Unless the "storage" cylinder is REALLY big one may not achieve enough vacuum for the silicon to lose the bubbles? 

True.
All you will achieve with this is an initial quick draw off, untill both vessels are balanced. If you then want further vacuum , the pump must suck on both, unless the spare tank has an isolation valve.

I think that doing this will also cause your rtv to bubble over at the sudden drop of pressure, so maybe not such a good idea for this application.

 

[tackle whore]

AndriesH wrote:

I think that doing this will also cause your rtv to bubble over at the sudden drop of pressure, so maybe not such a good idea for this application.

but once out of vacume wont bubbles reform again ?...... Hell i will just stick to wood and lead these i know .

 

[AndriesH]

Hi Mark.

No they won't.
The air is trapped in the mix when stirring it up, so once out, it stays out, unless you start stirring the mix again.


I think it wise to acknowledge what a couple of guys had said about  "worth the ffort or not "
Bennie has big plans for reproduction, while most of us make once off's.
IF you get a bubble in your mould / casting, it should take 5 minutes to repair, unless you are doing 50 castings.

 

[PH]

@AndriesH: Yours is a great idea and I'm sure it will work for vacuum molding which Bennie also has in mind. One does not need the serious vacuum for this type of application, I would imagine.

 

[tauruck]

I don't really want to get involved.

This is lure making.

Vacuum chambers are overkill IMHO.

The stuff being proposed here could suck an elephant through the eye of a needle.

I've worked with RTV for 25 years and air entrapment has never been a problem.

Get an electronic scale and use that to weigh out your materials.

That way you get the correct ratio of RTV to hardener because these materials are formulated to give ample time for air entrapment to escape during initial cure.

Your bubble problem is due to over catalysing the rubber.

My vacuum pump pulls 150cubic feet/minute and pray tell, why would I use it to get rid of a few bubbles???

Get a venturi pump system. You run it off your compressor.

AMT sells them along with a NON RETURN VALVE that will enable you to hold vacuum in your home made chamber long enough to expel those nasty bubbles that bug the hell out of you.

It won't break the bank either.

If that doesn't float your boat I can sell you an autoclave 1,2m diameter x 2m long for R90,000. Bargain of the decade.

This will do the job 100%.

 

 

[Fly Fish]

tauruck wrote:

I don't really want to get involved.

This is lure making.

Vacuum chambers are overkill IMHO.

The stuff being proposed here could suck an elephant through the eye of a needle.

I've worked with RTV for 25 years and air entrapment has never been a problem.

Get an electronic scale and use that to weigh out your materials.

That way you get the correct ratio of RTV to hardener because these materials are formulated to give ample time for air entrapment to escape during initial cure.

Your bubble problem is due to over catalysing the rubber.

My vacuum pump pulls 150cubic feet/minute and pray tell, why would I use it to get rid of a few bubbles???

Get a venturi pump system. You run it off your compressor.

AMT sells them along with a NON RETURN VALVE that will enable you to hold vacuum in your home made chamber long enough to expel those nasty bubbles that bug the hell out of you.

It won't break the bank either.

If that doesn't float your boat I can sell you an autoclave 1,2m diameter x 2m long for R90,000. Bargain of the decade.

This will do the job 100%.

 

Hi Mikey

Did you not mean 1.5CFM ?? 150CFM pump will be the size of a car

 

[tauruck]

Yup the car stuff.

This thing ain't no electrolux bru.

I can carry moulds around by the pipe that's attached.

This thing is the stuff they use in aerospace vacuum technology.

It would normally be mated to the 9m x 2m autoclaves used in the aircraft industry.

 

[Ruff_Ryder]

This has gone too far!!!!!

 

[benniejordaan]

tauruck wrote:

I don't really want to get involved.

This is lure making.

Vacuum chambers are overkill IMHO.

The stuff being proposed here could suck an elephant through the eye of a needle.

I've worked with RTV for 25 years and air entrapment has never been a problem.

Get an electronic scale and use that to weigh out your materials.

That way you get the correct ratio of RTV to hardener because these materials are formulated to give ample time for air entrapment to escape during initial cure.

Your bubble problem is due to over catalysing the rubber.

My vacuum pump pulls 150cubic feet/minute and pray tell, why would I use it to get rid of a few bubbles???

Get a venturi pump system. You run it off your compressor.

AMT sells them along with a NON RETURN VALVE that will enable you to hold vacuum in your home made chamber long enough to expel those nasty bubbles that bug the hell out of you.

It won't break the bank either.

If that doesn't float your boat I can sell you an autoclave 1,2m diameter x 2m long for R90,000. Bargain of the decade.

This will do the job 100%.

 

I do use an electronic scale, but I don't want to use Mouldmax 30. I find it's too flimsy, I want to use materials that are more rigid.
Curing Silicones on the coast is much faster with the level of humidity here.

As has been stated before, it is not absolutely necessary - agreed. But if you are casting materials that expand the air bubbles are a problem. Also if casting lead, it's a problem, because the air in the mould expands blowing the bubbles up, deforming the mould.

An autoclave is a pressurised oven. Not sure how the heat will help. In our industry we use them to cure rubber. Also used in the medical idustry to sterilise equipment.

 

[tackle whore]

well if you said a sterilizer oven it would be easy . can get my hands on 2 small ones .