Vacuum pump,question

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Forum topic by Robert posted 01-28-2018 10:19 PM 625 views 0 times favorited 8 replies Add to Favorites Watch
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3748 posts in 2256 days

01-28-2018 10:19 PM

Can I use an AC vacuum pump for veneer bag?

-- Everything is a prototype thats why its one of a kind!!

8 replies so far

View Loren's profile


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#1 posted 01-28-2018 10:46 PM


View bigblockyeti's profile


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#2 posted 01-29-2018 04:19 AM

Should be a perfect application for such a pump. If you’re planning on running it for a long time make sure it oil lubed and not oiless.

-- "Lack of effort will result in failure with amazing predictability" - Me

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#3 posted 01-29-2018 04:30 AM


-- Live to tell the stories, they sound better that way.

View wuddoc's profile


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#4 posted 01-29-2018 05:44 AM

You may wish to visit Joe Woodworkers website that is filled with information.

Here is the section on vacuum press:

-- Wuddoc

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3179 posts in 2270 days

#5 posted 01-29-2018 12:12 PM

Yes. One caution:
Have done a lot of vacuum bag composite lamination work, and can share that will not need low vacuum capabilities of typical refrigeration/A vacuum pump. Standard plastic vacuum bag materials can/will fail if you use too much vacuum. So when using any “high” vacuum pump (<1000um capable), and you will need to add a bleed off valve, or some type of automatic vacuum control valve monitoring the bag pressure.

Since it is almost impossible to have zero leak vacuum bag assembly, you typically leave pump running until the assembled is cured. This creates problems for refrigeration pumps: With many leaks, you may need more cfm than refrigeration pump is capable of pulling, or If you have minimal leaks, must have something to limit the pump from creating more 27-28 inches of vacuum in bag. Be sure you have a pressure gauge near the bag entry point.

If run vacuum bag assembly for long period without bleeder/control, once you are able to pull 29+ inches vacuum on a bag assembly, you will likely walk away and then return to find the bag ripped open at seems (or holes in bag).

-- If it wasn't for bad luck, I wouldn't have no luck at all, - Albert King - Born Under a Bad Sign released 1967

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7873 posts in 3689 days

#6 posted 01-29-2018 01:12 PM

Adding to answer above, I used to use an old R-12 Refrigerant tank (about the size of a grill propane tank) to act as my vacuum reservoir. This allowed me to pull the correct amount of vacuum and the tank would help that vacuum to last longer, so I didn’t need to run the pump continuously. FWIW, I used to vacuum-bag wood veneer and fiberglass/spectra/carbon cloth onto Styrofoam airfoils when make RC sailplanes. Too much vacuum would crush the Styrofoam and distort the desired airfoil.

Also, you could always piggyback more than one vacuum reservoir can for added capacity.

-- HorizontalMike -- "Woodpeckers understand..."

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3748 posts in 2256 days

#7 posted 01-29-2018 02:00 PM

CaptK & HM – That was going to be my next question. Kinda figured it would pull to much vaccuum so I was thinking I could add a regulator but I see they’re pretty pricey.

I’ll try the reservoir idea got 3 friends in the AC business…...I also think you could fashion one from PVC pipe.

-- Everything is a prototype thats why its one of a kind!!

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Fred Hargis

6245 posts in 3269 days

#8 posted 01-29-2018 05:51 PM

What about getting the parts you need from Veneer supplies to turn the pump on/off to hold the needed vacuum?

-- Our village hasn't lost it's idiot, he was elected to congress.

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