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Tarohn
Newbie
Joined: 10 Dec 2009
Posts: 14
Location: Saint Joseph, Mo
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 Posted: Tue Feb 23, 2010 12:07 pm Post subject: PSI of vacuum tank |
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| I know I saw this somewhere but I can not find the post again. What PSI are you pulling your storage tank down to for the vacuum? |
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spektr
Master
Joined: 07 Jan 2008
Posts: 425
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| Posted: Tue Feb 23, 2010 12:48 pm Post subject: |
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| the magic number seems to be 25 inches, less than that and sometimes you will lack detail, of course, thats for PETG and ABS. Other plastics are much more forgiving and need far less vacuum |
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Tarohn
Newbie
Joined: 10 Dec 2009
Posts: 14
Location: Saint Joseph, Mo
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| Posted: Tue Feb 23, 2010 5:41 pm Post subject: |
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| spektr wrote: | | the magic number seems to be 25 inches, less than that and sometimes you will lack detail, of course, thats for PETG and ABS. Other plastics are much more forgiving and need far less vacuum |
Wow so that's about -12.5 PSI. Across a larger surface area that is a lot of inward pressure. I was thinking about making my own and still may but going to have to really do some thinking about it first.
With a 24 X 24 inch platen with 1/2 spacer that gives me about 1.25 gallons of dead space. What kind of volume do you think would be needed? My thought is a 20 gallon or so tank would good.
Now before anyone warns me of the dangers of making a tank I completely understand and know whats involved. |
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jdougn
Guru
Joined: 18 Mar 2009
Posts: 714
Location: Louisville KY area
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| Posted: Wed Feb 24, 2010 7:50 am Post subject: |
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| Tarohn wrote: | Wow so that's about -12.5 PSI. Across a larger surface area that is a lot of inward pressure. I was thinking about making my own and still may but going to have to really do some thinking about it first.
With a 24 X 24 inch platen with 1/2 spacer that gives me about 1.25 gallons of dead space. What kind of volume do you think would be needed? My thought is a 20 gallon or so tank would good.
Now before anyone warns me of the dangers of making a tank I completely understand and know whats involved. |
Well, the danger depends upon your skill level and what materials the "tank" is made from. I used an old air compressor tank that I got for free.
DougN
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DougN - Just in case you're wondering, I got my "rating" legitimately... by posting aimless drivel, useless advice, and pointless questions. |
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stormtrooperguy
Expert
Joined: 24 Sep 2009
Posts: 126
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| Posted: Wed Feb 24, 2010 11:50 am Post subject: |
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| I've got 2 10 gallon tanks on my 2x2 that I can pull down to 26". I haven't formed anything yet so I can't say how awesome it is, but from what I've read, that should be a good medium performance system. |
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Tarohn
Newbie
Joined: 10 Dec 2009
Posts: 14
Location: Saint Joseph, Mo
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| Posted: Wed Feb 24, 2010 9:30 pm Post subject: |
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| I am leaning toward a tank that will be about 30 gallons. I have access to steel to about 1 inch thick. I will run the numbers but I am sure that it will be fine. |
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Hirgon
Newbie
Joined: 15 Jul 2007
Posts: 20
Location: Edmonton Alberta Canada
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| Posted: Wed Feb 24, 2010 10:19 pm Post subject: |
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| I am running a single 20 gallon air compressor tank....so far no problems with pulls. |
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stormtrooperguy
Expert
Joined: 24 Sep 2009
Posts: 126
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| Posted: Thu Feb 25, 2010 12:49 am Post subject: |
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| Tarohn wrote: | | I am leaning toward a tank that will be about 30 gallons. I have access to steel to about 1 inch thick. I will run the numbers but I am sure that it will be fine. |
just for curiosity, why go through the fuss of building your own tank? it seems like the raw materials would cost almost as much as buying one, never mind the labor... |
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Tarohn
Newbie
Joined: 10 Dec 2009
Posts: 14
Location: Saint Joseph, Mo
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| Posted: Fri Feb 26, 2010 12:04 pm Post subject: |
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| stormtrooperguy wrote: | | just for curiosity, why go through the fuss of building your own tank? it seems like the raw materials would cost almost as much as buying one, never mind the labor... |
I am sure that normally the material would cost as much as just buying a tank but I have access to the steel for $.05 lb if I nest the part I want cut into other things being cut. I am guessing that it will weigh about 100 lbs so thats only $5.00. We also have all the welders here that can weld the thicker steel ok. Now I dont have the skill to do that kind welding but have a couple of friends here that do.
Plus I just like building stuff  |
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stormtrooperguy
Expert
Joined: 24 Sep 2009
Posts: 126
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| Posted: Fri Feb 26, 2010 3:17 pm Post subject: |
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that makes sense then!
i'm happy with the $40 / 10 gallon tanks i got at lowes, but $120 for 3 of them is a lot more than $5!! |
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jegner
Site Admin
Joined: 30 May 2003
Posts: 2144
Location: Texas, USA
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| Posted: Sun Feb 28, 2010 6:10 pm Post subject: |
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Thurston James suggests a 30 gallon tank for a 24x24 size machine. 20 gallons is good in you don't have any loss of vacuum or your platen seals up nicely, the 30 gal. tank offer a bit more reserve.
Old hot water heater tanks are all the rage for this type of thing. 15 psi is about all there is as absolute vacuum is different than high pressure stuff. |
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trapperdale
Expert
Joined: 07 Jun 2009
Posts: 106
Location: fresno, california
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| Posted: Mon Mar 15, 2010 1:33 am Post subject: re |
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welding / building pressure vessels...
dangerous!
after all welding is completed you must naturalize the entire tank!!!
if not done the welds will fatigue crack and fail in a bad way...
the tempature and time duration depend on material used. |
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