Vacuum pump

[homebrewed]

Done, I bought the Yellow jacket YJII. Thanks again for all your help.

As a complement I´m thinking in one of these vacuum chambers.



But working with vacuum, the risk of implosion scares me a bit. The transparent lid is made of acrylic. Has someone here experience with theses things? Are they safe?

Thank you

In your case the difference in force acting on the lid with an OK vacuum vs. a really good vacuum is small. If that vacuum chamber was designed to handle 28-29" of vacuum you should be alright. But if I was doing stuff like that I'd be inclined to make myself a plywood box to enclose it. Or at least put it behind a shield of some sort. Cheap insurance, eh?

Something else to think about -- if that vacuum chamber is between your pump and experimental vacuum tube apparatus, if something goes wrong it can help keep junk from getting into your vacuum pump. I think it's a good idea in that regard.

I've seen descriptions of experimenters making their own diffusion pumps but it doesn't look like it's all that easy to make one that works very well compared to commercial versions.

 

[Alberto-sp]

Thank you for the advice!

I have done some research and there are 2 options for the lid. Acrylic or tempered glass. Wich one is more tough?

 

[homebrewed]

Thank you for the advice!

I have done some research and there are 2 options for the lid. Acrylic or tempered glass. Wich one is more tough?

If you want tough you probably want to go with the acrylic. The tempered glass option might be better suited in situations where you are de-airing something that has solvents in it. I think removing bubbles is the primary use for vacuum chambers like the one you are looking at.

 

[Alberto-sp]

If you want tough you probably want to go with the acrylic. The tempered glass option might be better suited in situations where you are de-airing something that has solvents in it. I think removing bubbles is the primary use for vacuum chambers like the one you are looking at.

Ahh ok. But for example for epoxy it is ok acrylic right?

 

[homebrewed]

Ahh ok. But for example for epoxy it is ok acrylic right?

If the epoxy isn't thinned, probably OK. However, one thing I learned when trying to de-air epoxy with a vacuum pump is that it can froth over in a heartbeat if the pressure gets too low. I'm not sure what caused it -- dissolved water (or air??), some organic component with a a relatively high vapor pressure/whatever -- but it definitely caused problems for me in that regard. It was bad enough that I worried about the stuff getting into the vacuum pump (it didn't).

 

[Alberto-sp]

Thanks a lot for the warning!
i think I´ll go for the tempered glass since it will be easier to clean with incidents like the one you mentioned.

 

[taiwanluthiers]

Thanks for your answer. Is for making experiments with electricity, like CRT, tubes, etc...

You are going to need a turbo molecular pump. They are NOT cheap. A mechanical pump will NEVER EVER evacuate to that kind of a vacuum.



Look around universities to see if they got old electron microscope to get rid of... or at least stuff for coating SEM samples... you might be surprised.

In fact with high vacuum system it works in stages. First you pump down to around 100 microns with a mechanical pump. This is probably not the most critical piece here and any cheap ones will probably do.

Then what will happen at that vacuum is the turbomolecular pump will take over, and it will pump down to something like 5x10^-5 torr. You need that kind of vacuum before you can even entertain any sort of cathode ray, vacuum tube, or whatever. There's too much air in the thing otherwise that will get in the way of things. For reference 1 micron is about 1x10^-3 torr. So you are very far off indeed.

I used to work with SEM's and I was using a sputter coater made by LADD Industries. The thing has a mechanical pump and a turbo pump. The mechanical pump basically shuts off at around 100 or so microns and then the turbo takes over, and it took like 15-20 minutes before it reached the necessary sputtering vacuum. The unit costs about 40,000 dollars. I never had the privlidge of messing around with them though... I won't touch them because I know how expensive they are. The LADD Industries unit has numerous safety interlocks to prevent it from blowing up but imagine waiting hours and it wouldn't pump down to the necessary vacuum really hurts morale.

One alternative is you can use mercury drop to get you down to the necessary vacuum. There is a youtube video by Cody Labs about this. You basically use the weight of the mercury to pump it down and it takes DAYS to get there, but it will get you there.

You know those spinning thing when you shine a light on it? A 2 stage HVAC pump won't even pump down to where those will work.

Here's the video on the mercury thingie... it's called a Sprengel pump

 

[Alberto-sp]

You are going to need a turbo molecular pump. They are NOT cheap. A mechanical pump will NEVER EVER evacuate to that kind of a vacuum.

View attachment 438671

Look around universities to see if they got old electron microscope to get rid of... or at least stuff for coating SEM samples... you might be surprised.

In fact with high vacuum system it works in stages. First you pump down to around 100 microns with a mechanical pump. This is probably not the most critical piece here and any cheap ones will probably do.

Then what will happen at that vacuum is the turbomolecular pump will take over, and it will pump down to something like 5x10^-5 torr. You need that kind of vacuum before you can even entertain any sort of cathode ray, vacuum tube, or whatever. There's too much air in the thing otherwise that will get in the way of things. For reference 1 micron is about 1x10^-3 torr. So you are very far off indeed.

I used to work with SEM's and I was using a sputter coater made by LADD Industries. The thing has a mechanical pump and a turbo pump. The mechanical pump basically shuts off at around 100 or so microns and then the turbo takes over, and it took like 15-20 minutes before it reached the necessary sputtering vacuum. The unit costs about 40,000 dollars. I never had the privlidge of messing around with them though... I won't touch them because I know how expensive they are. The LADD Industries unit has numerous safety interlocks to prevent it from blowing up but imagine waiting hours and it wouldn't pump down to the necessary vacuum really hurts morale.

One alternative is you can use mercury drop to get you down to the necessary vacuum. There is a youtube video by Cody Labs about this. You basically use the weight of the mercury to pump it down and it takes DAYS to get there, but it will get you there.

You know those spinning thing when you shine a light on it? A 2 stage HVAC pump won't even pump down to where those will work.

Here's the video on the mercury thingie... it's called a Sprengel pump

Thank you for your answer. Mi idea is to use a HVAC machine (I got one that reach 15 microns/ 0,015 torr) and later use a titanium getter to reach a higher vacuum. I took the idea from this video

 

[taiwanluthiers]

Thank you for your answer. Mi idea is to use a HVAC machine (I got one that reach 15 microns/ 0,015 torr) and later use a titanium getter to reach a higher vacuum. I took the idea from this video

If your budget is limited then any HVAC pumps will do. They will reach about 15 microns after pumping for a while. The better two stage are really to allow techs to pump down in a shorter period of time, and if you are pumping down such a small volume, then having higher CFM doesn't matter so much.

How do you heat up the getter?

 

[Alberto-sp]

If your budget is limited then any HVAC pumps will do. They will reach about 15 microns after pumping for a while. The better two stage are really to allow techs to pump down in a shorter period of time, and if you are pumping down such a small volume, then having higher CFM doesn't matter so much.

How do you heat up the getter?

With a induction heater, you can see in the video in 1:04:38