warthog
Member
Would a 6cfm air vacuum pump be to much for removing he bubbles from your resin. I came across one today and was wondering if this is to much. Any help would be great...the guy isn't going to wait forever. Thanks.
Vacuum pump
- Thread starter warthog
- Start date
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louisbry
Member
If the price is right and it is in good shape, go for it. It will not pull more vacumme, but rather the vacumme will be quicker due to increased pumping volume than a lesser cfm air vacumme.
MesquiteMan
Retired Head Moderator
The vacuum pump that I use is 6 cfm. Like Louis said, it will not pull more vacuum since there is a limit on the amount of vacuum that is possible. It will just do it quicker.
Padre
Member
- Joined
- Dec 2, 2009
- Messages
- 1,841
I know I asked once before, but what type of pump do you have? I still need to get a good one.
Jim Dent
Member
From my understanding 3CFM or greater, is super.
MesquiteMan
Retired Head Moderator
Chip,
I am running a JB Industries JB Eliminator. I really like it because it is well made here in the US with parts available should I need them. Another good US made pump is Robinaire from what I hear.
Really, most any rotary vane pump out there will do a good job. Don't get too hung up on the CFM rating, rather look for the vacuum generated. A good pump should be rated to pull a 29" Hg vacuum. Most rotary vane pumps are rated in microns for vacuum so ideally, you want one that will pull 100 microns or less.
To show how unimportant CFM is, lets convert it to cubic feet per second and then do the math for how long it will take to evacuated a given space.
1 CFM is .0167 CFS (cubic feet per second)
2 CFM is .0333 CFS
3 CFM is .05 CFS
6 CFM is .1 CFS
My small chamber, for example, contains .075 cubic feet. Time to evacuate per CFM rating (only using common CFM pump ratings):
2 CFM = 2.72 seconds
3 CFM = 1.5 seconds
6 CFM = .75 seconds
My large chamber contains .259 cubic feet. Time to evacuate per CFM rating:
2 CFM = 7.848 seconds
3 CFM = 5.18 seconds
6 CFM = 2.59 seconds
Of course it will take a lot longer than the numbers above since this is the rating "at the pump" with no restriction such as the hose or even vacuum! In actuality, it takes 37.8 seconds for my 6 cfm pump to pull my large chamber with nothing in it down to 28.5" Hg which is maximum vacuum at my elevation. That may seem like a long time, especially if you are thinking about a lower CFM pump, but if I am actually stabilizing blanks, I can not pull it down that fast anyway because the amount of air coming out of the blanks cause the resin to foam significantly and so I need to gradually take it down by opening the bleed valve, allowing outside air into the pump. In my case, I am not even using anywhere near the full CFM of my pump.
BTW, I just have a simple business degree and am not a math wiz, so it is possible I am wrong on my calculations above. If so, someone please point it out so I can correct it!
I am running a JB Industries JB Eliminator. I really like it because it is well made here in the US with parts available should I need them. Another good US made pump is Robinaire from what I hear.
Really, most any rotary vane pump out there will do a good job. Don't get too hung up on the CFM rating, rather look for the vacuum generated. A good pump should be rated to pull a 29" Hg vacuum. Most rotary vane pumps are rated in microns for vacuum so ideally, you want one that will pull 100 microns or less.
To show how unimportant CFM is, lets convert it to cubic feet per second and then do the math for how long it will take to evacuated a given space.
1 CFM is .0167 CFS (cubic feet per second)
2 CFM is .0333 CFS
3 CFM is .05 CFS
6 CFM is .1 CFS
My small chamber, for example, contains .075 cubic feet. Time to evacuate per CFM rating (only using common CFM pump ratings):
2 CFM = 2.72 seconds
3 CFM = 1.5 seconds
6 CFM = .75 seconds
My large chamber contains .259 cubic feet. Time to evacuate per CFM rating:
2 CFM = 7.848 seconds
3 CFM = 5.18 seconds
6 CFM = 2.59 seconds
Of course it will take a lot longer than the numbers above since this is the rating "at the pump" with no restriction such as the hose or even vacuum! In actuality, it takes 37.8 seconds for my 6 cfm pump to pull my large chamber with nothing in it down to 28.5" Hg which is maximum vacuum at my elevation. That may seem like a long time, especially if you are thinking about a lower CFM pump, but if I am actually stabilizing blanks, I can not pull it down that fast anyway because the amount of air coming out of the blanks cause the resin to foam significantly and so I need to gradually take it down by opening the bleed valve, allowing outside air into the pump. In my case, I am not even using anywhere near the full CFM of my pump.
BTW, I just have a simple business degree and am not a math wiz, so it is possible I am wrong on my calculations above. If so, someone please point it out so I can correct it!
Last edited:
bradh
Member
The larger cfm pump is also usable if you want to do vacuum chucking on the lathe. A quick connect fitting and it can serve dual roles in the shop.