Hello everyone
I need to build 22” x 25” vacuum table for a special project i have coming up . I need to cut 500 pcs of 1/8” acrylic parts.
Will 12 CFM vacuum pump work?
I will be sealing all edges and tiles so i don’t lose any air.
Thanks
Hey Terryjames,
this is a wide topic and I would not buy vacuum technology without first aquiring some knowledge.
The required air flow rate is very dependent on the vacuum table you use. Grating tables work reliably with a vacuum pump with much less rated air flow, even on larger areas, than Hole grid tables which need considerably more air flow rate.
The technique with which you seal the area where your workpiece is held differs strongly.
Here is a link to a table (PDF) to choose the required vacuum pump air flow rate. Flow rate is given in m³/h. For conversion see below.
As you can see with a grating table on which you first seal the area under the workpiece with a sealing gasket, you need much less rated air flow rate on the pump. But these vacuum tables are more expensive.
With a hole grid table you need a considerably stronger vacuum pump as you usually loose much more air, but such a vacuum table is less expensive and you can do things like this 
Further reading
-
Air pressure is measured in Pascal (Pa) (often also given in SI-derived bar)
- (US/imperial: psi)
-
Volumetric flow rate is measured in cubic meter per second (m³/s)
- (US/imperial: cubic feet per minute (cfm))
1 m³/s = 60 m³/min = 3600 m³/h
1 m³/h = 1000 l/h = 60,000 l/min
1 l/s = 60 l/min = 3600 l/h
1 l/min = 60 l/h
In the SI system of units, the preferred unit for volumetric flow rate is cubic meter per second.
Liter / cubic meter conversion
1 l (litre) = 1000 cm³ = 1 dm³ = 0.001 m³
1 m³ = 1000 dm³ = 1,000,000 cm³ = 1000 l
Bar / Pascal conversion
1 bar = 100,000 Pa (= 100 kPa)
SI to Imperial and U.S. Customary Conversion:
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Thanks for all the info.
A little confusing mind you.
Can anyone recommend a pump that can handle 24” x 25” .
I do have a good shop vac 6 hp brand new. I just don’t want to burn out the motor. My longest cut is 7 mins long. Will the shop vac handle being on that long. I have like 500 pcs to cut out through the acrylic sheet.
Thanks
Hey Terryjames,
the air flow rate will strongly depend on how the workpiece sealing system will be on the vacuum table you plan to build. I hoped the Decision help – Vacuum pumps (PDF) table would help you.
I plan to use a vacuum table of similar size as you do, but also smaller elements sometimes, but I am not yet at the stage of final decision. But I think I will buy one of these, but you may also be better off with one of these.
I would always strongly avoid “oilless” or “dry running”, both on vacuum pumps and on compressors, since they often require disassembling and service after less than a year. Also I would avoid making vacuum with compressed air as the efficiency is low.
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Hey Terryjames,
I think I would not use my shop vac for this. A shop vac is usually driven by a universal motor with carbon-brush commutators which means
- loud
- frequent service needed in case of longer continuous use (carbon brushes replacement)
- poor electrical efficiency (high power consumption)
The pumps linked above have capacitor-start induction motors, which means
- more quiet
- no carbon-brushes to be serviced
- high electrical efficiency (low power consumption)
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I built a system I am happy with based run on a Gast rotary vane pump I found for a good price at an equipment surplus store in my area. I have it controlled by feedback from a pressure switch attached through an IOT power relay. I can set it to whatever trigger vacuum level I feel comfortable with. It is part of an aluminum vacuum fixture plate system I am designing. It holds extremely well in testing.
If I had a project like yours, I might design a custom sub plate to use between the main plate and my parts, so that both internal and external cuts can be made cleanly without risk of damaging the (in my case) aluminum vacuum plate.
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Thanks for all the input it’s very helpful
I was thinking of the Fein vacuum I can get one for about $400 with free shipping. I heard it works very well.
I’m going to test a few things and look into some vane pumps as well.
Thanks again.
Hi
Do you know do these let off a lot fumes?
If your system is well sealed, they don’t smoke much. If you’re moving a lot of air and not achieving deep vacuum, you will see smoke after a while. Not the nicest thing to deal with TBH.
How big is your acrylic part? I’d recommend designing a dedicated fixture with ports and surrounding gasket zones under each part to hold it firmly in place until it’s finished. You have a lot to make and the fixture plate will save you a ton of time in the end by eliminating tabs, etc. Depending on your sheet yield and part shape, you may also need to account for large pieces of left over material to avoid sending those ninja stars flying. And also consider any internal cuts that go thru and seal those off as well.
Sounds like a great project!
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I have been using the gast pump that rockler sells, but on my 24" x 24" vacuum clamp, it really needs the seal to be excellent and a smooth surface on the wood/plastic I am cutting. I don’t see any fumes out of mine.
I am about to pull the trigger on a pump that airweights sells, since the vacuum clamp is from them and the owner seems to think it is a good match for the system, and rated to a higher flow rate. AirWeights Vacuum Pump
I think what it comes down (after core ability to function) to is expected lifetime of the pump. If you are planning to knock out a few projects and short cuts, then the A/C pump down vacuum may suffice. Otherwise I’d recommend something known to last, like the recommendations shared above. 
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Hey Terryjames,
here is a Shop vac vs. Vane pump comparison. Besides what I mentioned above to consider…
…here someone compared both and measured pressure and holding force:
I appreciate the insights from @Aiph5u and others in this thread. Over the weekend before I saw this thread I was experimenting with a small used vacuum pump for workholding with mixed results. I ended up ordering a used Gast DOA-P701-AA diaphragm pump similar to the Rockler pop pump I think was mentioned above. 1.1cfm, 4.14 bar… I’m intrigued about the possibility to potentially use it in some cases for vacuum pumping, and other times to experiment with as a chip blowing compressor… we’ll see how that goes when it arrives 
if there’s one thing for certain, high powered continuous runtime vacuum pumps are expensive!
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You pretty much forced my hand on this one…
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