Vacuum Pump

[ranchak]

I'm looking for a vacuum pump for de-gassing silicon and urethanes, any recommendations? I don't want nor can I afford a complete setup. I have a 2 gal paint pot, so I really only need the pump. Can a Robinair pump that is used in HVAC pull enough vacuum to de-gas?

[Geof]

Yes if it is working correctly. You will need to make sure there are no leaks in your system becasue these pumps have a limited pumping capacity.

I take it you have not done any vacuum degassing like this before? It can get really messy. At the point where the vacuum is strong enough that the mixture starts degassing it can foam up to several times its volume spilling out of the container and getting into vacuum lines. Start off with a very small sample in your bigger container and if you can rig a second container ahead of the pump as a trap it is a good idea. Vacuum pumps don't work very well when they are full of silicone.

Years ago I did quite a bit of silicone degassing with a system using an open top tank something like a paint tank and found the best approach was to put a thick piece of acrylic on the top so I could watch what was happening and open a vent valve if the foaming was getting out of hand. Once the degassing is complete the mix settles back down and the casting results with properly degassed material are far better than you can get without degassing; well worth the hassle.

[rowbare]

To get an idea of what Geof is talking about check out the videos at: http://www.freemansupply.com/video.htm

In several of them they show the vacuum degassing process and you can get a sense of how the mixture expands before collapsing.

[ranchak]

I've seen the video already, that's what got all of this started. I've been looking for a pump and there are too many choices, so I figured I see what you guys are using and if it fits in the budget then I'll get one. So what are you guys using?

[ranchak]

This pump caught my eye:

http://cgi.ebay.com/ws/eBayISAPI.dll...m=220390939520


I really don't wan't to spend this much, but I know you get what you pay for.

[ger21]

Check Surplus Center. I got a Gast pump there for $90

[ckirchen]

http://www.veneersupplies.com/produc...oducts_id=1099

I bought one of these for vacuum clamping, but it should work well for degassing. They have others that are bigger; click "Vacuum Press Parts" and scroll about halfway down.

Chris Kirchen

[ranchak]

ckerchin, thanks for the link. I'm going to give one of their venturi pumps a try.

[ckirchen]

Originally Posted by ranchak I'm going to give one of their venturi pumps a try.

Make sure your air compressor has the available CFM to handle it.

I was going to get a venturi, until I realized that my compressor would have to provide 5 cfm to make about 3 cfm. That's why I got the pump I posted instead.

Might not be a factor for you though. Just thought I'd put it out there.

Chris Kirchen

[ranchak]

Chris, I have 10cfm @90psi, it won't be perfect, but will definately work. The V2 "requires" 7.8CFM @80 so I will be close when you figure in the flow restriction with fittings. I'm going to use large vacuum reservoir tanks to aid in pulling down the vacuum. I also plan on using this system to hold some parts that I have to mill.

[ckirchen]

Originally Posted by ranchak Chris, I have 10cfm @90psi, it won't be perfect, but will definately work. The V2 "requires" 7.8CFM @80 so I will be close when you figure in the flow restriction with fittings. I'm going to use large vacuum reservoir tanks to aid in pulling down the vacuum. I also plan on using this system to hold some parts that I have to mill.

That won't leave much CFM left over for anything else. It also means that you compressor will be running at almost 100%.

Why not use an electric pump with those same tanks? My Rietschle Thomas from Veneer Supplies needs new seals, but it has run (in always on mode) eight hours a day for the last two years. I can't imagine how a compressor would have faired after the same duty, a bunch of oil changes at the minimum; plus the compressor is much noisier.

Chris Kirchen

[ger21]

I use a Joewoodworker venturi pump for veneering. Imo it should work just fine for what you want to do, provided you have a decent size reservoir, and your degassing chamber isn't a lot larger than the reservoir.