Can Vacuum Holding Be Done Inexpensively, Without a Huge Compressor?

Hello, Hello.

I've begun exploring building a small DIY vacuum table. I don't need a footprint much larger than 24" x 24"

Excuse my ignorance, but is there a way to create a vacuum-holding system without needing a huge compressor (which I do not have) or a large vacuum pump (which I also don't have) -- in other words, without spending a bucketload of money? My work-piece is made from plastic, measures less than two inches across, and weighs less than and ounce, so I don't need a huge amount of suction. You guys are always full of great ideas and know-how.

Thanks in advance for sharing your expertise.

#5

So ,you dont have a compressor,and dont want an exhauster (correct term for a vac /pump)......well, then ,how about steam?...Two ways (at least) with steam....condense the steam in a closed vessel ,instant sub atmospheric pressure.James Watt invented that...Or use a steam ejector to remove air via a venturi.....noisy ,and needs a boiler @50psi+,....but very high capacity......then there is the simplest way to do it.......hook up the intake manifold of a carburetted engine to your vac project...typical idling is close to half atmospheric.

There are a number of ways to achieve a vacuum. A large pump is only necessary if your system or jig has a lot of leaks. If you have only a few, small leaks, then even a low volume pump can work.

If your work piece is less than 2" x 2", why do you envision a 24" square table? I would make a table that is just big enough for the work you are doing. If you later have larger pieces to work on, then just build a larger table to fit them. The volume of air in the table is what has to be evacuated. The larger that volume, the longer it will take to do so or the larger the pump you will need to do it in a fixed amount of time.

You do not say what you will be doing to the work piece. Drilling? Milling? Surface grinding? What? Different operations will need different amounts of grip. But here is the kicker: even with a perfect vacuum, you can never get more than atmospheric pressure on the work piece. That is about 14.7 pounds per square inch at sea level. So for a 4 square inch work piece (2" x 2") the largest clamping force you can get is four times that or 58.8 pounds. With a table with holes in it's surface, that will be reduced by some factor. You need to be sure that amount of clamping force will be enough for the operations you have in mind. If you are thinking of making that 24" square table with a whole bunch of holes all over it and just putting a 2" x 2" part down on it while the rest of the holes leak air, you are going to need a really expensive, high volume pump.

There are small vacuum pumps. Probably with a range of prices. Just a quick search, which you could have done yourself "vacuum pump":

vacuum pump - Google Search

Other ways of creating a vacuum include things like hand pumps, vacuum cleaners, squeeze bulbs, blowers, and venturi that create a vacuum from a flowing stream of compressed air. Even pumps for athletic equipment can sometimes be reversed to pull air out instead of pumping it in.

The two things you need to know and are looking for are the level of vacuum they can produce and the volume of air they can evacuate in a given amount of time.

I have made jigs for making wood parts that used a shop vac to provide the vacuum needed to hold the parts in place while they were being cut. That jig did not leak a lot of air and the parts were braced in other ways in addition to the vacuum so the shop vac worked well.

Perhaps if you told us more about what you are doing, we could be of greater help.

you can connect a venturi contraption to you faucet.

Use a Shop vac

How much vacuum pressure do you need? A household vacuum cleaner can develop quite a bit of holding power if the surface area is large enough - as long as the air-over rated vacuum motor receives enough airflow to remain cool during operation.

Otherwise check Facebook Marketplace and Craigslist for used vacuum pumps. They can be had for around $60-100.

We used to do 6 X 8 inch sheets of plastic using a small vacuum pump. Milled shapes with a 1/8 endmill almost all the way through and broke the shapes out after changing the sheet. With many times the surface area you should have an easy time of it. Seems like we had 24+ inches of vacuum. We finished the plate well then black anodized it to show up any stray chips that would have interfered with the vacuum seal.




Just in case any of your work needs to be moved to a lathe we held the same square parts made on the mill in vacuum plates on the lathe. Smaller area required the fence around the squares but 100% successful with never a thrown part.
Sizes were 52mm, 62mm, and 102mm square.

How long does the vacuum need to be applied?

If it's not too long, you could use a normal vacuum pump (like for evacuating AC systems) and a big vacuum tank for capacity. Once the tank has 28 inches of vacuum, start your process and between the tank and the pump capacities, you'll have vacuum for a good while.

It all depends on the amount of time the work must be held and how much leakage there is.

It is possible to buy vacuum reservoirs that can maintain vacuum for a time after being slowly evacuated by a small vacuum pump or even a compressed air siphon. The cost may not be that low however.

Venturi pumps are $70ish for what I use. Mine is good for 27" of vacuum and uses .4 cfm of compressed air.

Do not use anything other than a real vacuum pump to create a vacuum. If you try to use a blower, like a vacuum cleaner, to create a vacuum, it will destroy the motor of the blower.

For what you are doing you can use an ordinary Gast laboratory vacuum pump. You can get them for about $100 on eBay:

Gast DOL-101-AA Vacuum Pump (R22) | eBay

I would try double sided tape, or spray adhesive before I messed around with a vacuum fixture for such a small piece, as long as cosmetics aren't a huge issue. We mill .005" and .010" shim stock using 3m spray adhesive.

One of the accessories I bought for my Ryobi 10" table saw is a vacuum table top that fits on the saw table extensions. It is neant to hold smooth pieces of wood while sanding or routing. It has a fitting to connect the hose of a standard size sawdust collector or shop vac and has a Formica-type top surface with lots of holes. You need to mask off the exposed holes around the part with sheet rubber or similar. The top can be attached to any sort of stand and just needs a shop vac to work. I think I paid around $100 twenty years ago and never used it

At the other end of the quality spectrum is my Walker 12 x 18 vacuum chuck for my surface grinder. It is solid steel and precision ground. Looks nice, but I never needed it either.

Keep in mind that the smaller the part, the less the force of atmospheric pressure acting to press it against the table. The most pressure you can get is about 14.7 psi with a perfect vacuum.

Larry

How is the guitar pick biz going??
Resurrection an old user name because you were bounced out of her under the old one?
Back to ask more questions ( educatedguess417 ) until someone replies with the answer you want to hear?

And here I am sitting on an unused Gast vacuum pump which would be perfect for your needs. A bit heavy to ship, but we can fix you up with a bargain. PM me if interested.

jack vines

You can always add a "leak" to lighten the load on the motor. Some of the vacuum hoses even have this kind of port built in. It's not rocket science. Dirt cheap!

And if you just search, vacuum pumps can be had for FAR less than $100. Just start looking.

jscpm said:

Do not use anything other than a real vacuum pump to create a vacuum. If you try to use a blower, like a vacuum cleaner, to create a vacuum, it will destroy the motor of the blower.

For what you are doing you can use an ordinary Gast laboratory vacuum pump. You can get them for about $100 on eBay:

Gast DOL-101-AA Vacuum Pump (R22) | eBay

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Be careful with using double sided tape. I have a 6" face plate sitting in my shop with a layer of 3/4" plywood stuck to it with double sided tape. I never could get it separated. I just use it when I need a sacrificial pressure plate in the lathe.

Mike1974 said:

I would try double sided tape, or spray adhesive before I messed around with a vacuum fixture for such a small piece, as long as cosmetics aren't a huge issue. We mill .005" and .010" shim stock using 3m spray adhesive.

Click to expand...

In case any of the readers are wondering about the use of two different terms for measuring vacuums, here is the correlation:

Traditional barometers used mercury as the working fluid. The air or gas pressure was measured in terms of how high of a column of mercury could be held up by that pressure (referenced to a total vacuum). So we came up with the unit "inches of mercury" as a standard measure of atmospheric pressure.

Of course, gas or fluid pressure is directly measured in terms of weight per unit of area or pounds per square inch (PSI).

There is a simple, direct conversion factor between these two units of pressure:

29.92 inches Hg = 14.7 pounds per sq in (PSI)

The abbreviation "Hg" is the chemical symbol for mercury.

Thus, with a little bit of rounding, 30" of Hg is just about the limit of how strong a vacuum can ever be. When numbers like 29" or even 27" of vacuum are thrown around, that is a pretty good vacuum. 10" or 15" or less would be a poor one.

I used the 14.7 PSI number in my previous post because it more directly correlates to what is being done; namely, clamping.

Barometer - Wikipedia

Atmospheric pressure - Wikipedia

2" is a small part for vacuum fixturing. Not much area, so not much holding.

My big commercial pump locked up last year so in an emergency I bought this one , Im pretty impressed
McMaster-Carr Its a gast also

works perfectly and keeps up with production with no problems. I havent tried it on 2 separate machines yet, but use it on one cnc mill with 3 fixtures at once.
not to mention its super quiet.