snowman
Diamond
- Joined
- Jul 31, 2004
- Location
- Southeast Michigan
I have a need for a vacuum chamber that is approximately 8" tall and 24" in diameter. Operating temperature is room temp.
Vacuum at the range of x10^-6 torr, so just getting in to molecular flow, but nothing nasty that takes days to pump down. The vacuum is really just to rid the environment of oxygen.
I've worked with high pressure a reasonable amount, but never at the other end of the spectrum. High pressure, you just tighten it a bit more. Vacuum...well, not quite the same.
My biggest design motivator right now is honestly cost, I need to do it on the cheap. That doesn't mean free, just cheap. I am using off the shelf surplus parts for a majority of it, but the chamber is just not available. I have a good roughing pump and a diffusion pump, all mounted in a nice rack with ion gauge.
This won't be a dive in and hope you can swim project...but it sort of is at the same time. I don't have the budget to have it custom made by a shop that specializes in vacuum.
BUT...I know there are some sub-atmospheric pressure guys here.
Right now, my thoughts are simply a sandwich of ~1" thick 6061 aluminum plates that have an o ring groove milled (high speed, carbide, air jet coolant, ramp down not dive, polish any lines that aren't concentric)....but what to use for that spacer to get the depth?
I can have a piece of stainless rolled, then get a couple of flanges made up, then weld it on (stitch welded on outside for strength, fusion weld on inside for seal). But, instead of flanges, would it be foolish to try to roll stainless angle, weld it up, then machine it flat and polish it?
I have also considered just getting some "thick" rings of aluminum water jetted and stacking them, of course with appropriate seals and such.
My understanding is that at x10^-6, I'm not yet in to the range where I'll see wicked virtual leaks from off gassing of non-electropolished material...but I'm also inexperienced.
Any ideas?...
Vacuum at the range of x10^-6 torr, so just getting in to molecular flow, but nothing nasty that takes days to pump down. The vacuum is really just to rid the environment of oxygen.
I've worked with high pressure a reasonable amount, but never at the other end of the spectrum. High pressure, you just tighten it a bit more. Vacuum...well, not quite the same.
My biggest design motivator right now is honestly cost, I need to do it on the cheap. That doesn't mean free, just cheap. I am using off the shelf surplus parts for a majority of it, but the chamber is just not available. I have a good roughing pump and a diffusion pump, all mounted in a nice rack with ion gauge.
This won't be a dive in and hope you can swim project...but it sort of is at the same time. I don't have the budget to have it custom made by a shop that specializes in vacuum.
BUT...I know there are some sub-atmospheric pressure guys here.
Right now, my thoughts are simply a sandwich of ~1" thick 6061 aluminum plates that have an o ring groove milled (high speed, carbide, air jet coolant, ramp down not dive, polish any lines that aren't concentric)....but what to use for that spacer to get the depth?
I can have a piece of stainless rolled, then get a couple of flanges made up, then weld it on (stitch welded on outside for strength, fusion weld on inside for seal). But, instead of flanges, would it be foolish to try to roll stainless angle, weld it up, then machine it flat and polish it?
I have also considered just getting some "thick" rings of aluminum water jetted and stacking them, of course with appropriate seals and such.
My understanding is that at x10^-6, I'm not yet in to the range where I'll see wicked virtual leaks from off gassing of non-electropolished material...but I'm also inexperienced.
Any ideas?...