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IndustryArena Forum > WoodWorking Machines > DIY CNC Router Table Machines > Vacuum Pump, Who uses them and What do you use?
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  1. #1
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    Vacuum Pump, Who uses them and What do you use?

    Do you use a vacuum pump on your machine? Did you make it? Did you buy it? Are you happy with it?

    I'm thinking of getting one. But have no idea what way to go. Try making one, buy one, how big do I need etc.

    I'd love to see pics of your setup.

  2. #2
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    Re: Vacuum Pump, Who uses them and What do you use?

    http://www.cnczone.com/forums/work-f...56288-cnc.html

    I put this one together and I'm currently finishing up the connection to the router bed. Did some testing on it two days ago and it pulls a really strong vacuum and flows at least as much as a shop vac. Any serious vacuum system that I found was several thousand dollars. ~ $2500 for a good size Re-gen blower from China.

  3. #3
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    Re: Vacuum Pump, Who uses them and What do you use?

    I've used closed environment vacuum for work holding on and off for years. A closed environment is one where you can control your leakage, which is different than the systems that use a high horsepower regenerative blower to suck material down thru a waste board like MDF.

    A closed environment is one where your material is not porous, or at least not porous enough to leak so bad you can not make up enough vacuum volume to make up for those leaks. You generally create a jig out of a non porous material, put closed cell foam tape around the boarders (and strips in the middle to hold the part up and keep the middle from bowing, then apply vacuum into the created cavity.

    If you have practically zero leaks, you can get by with a simple 1/3 HP Gast vane type pump. Quiet, cheap to run, and far better than an air compressor powered vacuum venturi if you have a small shop running a piston pump compressor. No need to run a 5hp compressor if you only need 1/3hp worth of vacuum. Larger pumps will create more volume of vacuum, not necessarily higher vacuum levels, and can make up for more leakage. If you search surplus sites for rotary vane vacuum pump, you should find some reasonably priced.

    Of course you can run your vacuum pump into a tank thru a check valve, and have high volumes of vacuum available for coverage during momentary leaks.

    I've built some radical vacuum systems that used small pumps for tank "maintenance", but much larger pumps kicked in if anywhere in the company a major leak was created. Losing vacuum in a shop where more than one person is relying on it can be dangerous.

    At my home shop, I simply have a 3/4 hp Gast rotary vane pump mounted on an old air compressor tank. A switch cycles it on and off as necessary, leaving me with a vacuum source available at any time. It is amazing what 15-25 inches of vacuum will hold.... I would not be without it.
    Chris L

  4. #4
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    Re: Vacuum Pump, Who uses them and What do you use?

    I have a bunch of vacuum pumps in various sizes and types. My experience has been that more powerful pumps usually produce a stronger vacuum. The specs aren't always linear (I.e. A 2hp is not necessarily twice as strong as a 1hp pump) but the manufacturers usually state how much of a vacuum they can produce as part of the specs, so no need to speculate.

    My experience has also been that larger motors equal more noise regardless of the type of pump. My 3/4hp pumps are noticeably louder than my 1/8hp pump.

    Also, and more importantly, low power pumps often overheat and stop working (I.e. Switch off) when you task them with holding a vacuum for a prolonged period. I usually have them running for 10-24 hours per job. While there is no universal "right size", you want to make sure that you get one that is powerful enough for the job and rated to hold a vacuum (not just suck air and water like an air conditioning pump) and one that is rated for continuous use so it will last over a long CNC job.

    Quality new vacuum pumps cost a lot. Too much imo for any diy project but.... quality used pumps are relatively cheap and plentiful on eBay. I got one of my 3/4hp Thomas oil free pumps for less than $50. Cheap new pumps are to be avoided like the plague.

    btw, the same thing applies to new and used vacuum tables on eBay. I have seen relatively large used aluminum vacuum tables go for a fraction of the new price. A lot of them seem to come in "cells" so you can choose the right number of cells for the size of table/ part and add more if needed. I think the requirement will be based more on the size of parts to be held down than the overall table size.

    I don't plan on using a vacuum table as, for my application, I believe bolting the work down will be more reliable, but, if I was going to use one, they are relatively easy to make. You can use a similar design to those vacuum forming tables (where plans are readily available online) except I would want to make one out of something a lot stiffer than wood and with better seals. A flexing table can't be good for holding a vacuum or accurate CNC work...

    I would probably start with some aluminum tooling plate as it's stiff and comes precision flat out the box. With that said.... it's expensive in larger sizes.... might be cheaper to buy a quality used vacuum table.

    That's my $0.02 on vacuum pumps. It's one of the few areas where I had consistently good luck in finding high quality / low cost used equiptment.

  5. #5
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    Quote Originally Posted by TTalma View Post
    Do you use a vacuum pump on your machine?
    .
    Nope. Mainly because i dint have a personal machine at the moment and i would tend to avoid vacuum work holding if i did. However we use all sorts of vacuum pumps at work and can say you have a massive selection to choose from.
    Did you make it? Did you buy it? Are you happy with it?

    I'm thinking of getting one. But have no idea what way to go. Try making one, buy one, how big do I need etc.
    The first thing to understand is how vacuum clamping works and its strengths and weaknesses. First understand that all you get is atmospheric pressure as the clamp force. So if you are lucky 14PSI.

    Frankly 14 PSI isn't much in many situations but excels when you have large up machined surfaces. For small intricate work it can be especially useless.

    The first thing you need to do is to determine if vacuum hold down is right for you and your processes. If it is one can go on from there.

    Generally you need to understand two specs for the pump you are looking at. One is the ultimate pump down level the pump can reach. The other is the volume of air a pump can move. How far you can pump down impacts achievable clamping forces. The volume capability of the pump tells you how fast you can reach that level and how well the pump will handle leakage.

    Leakage can be a huge problem and can vary drastically with the project at hand. So before you pick a pump and frankly before you even consider one, you need to consider how leakage will impact your usage. Given that most router implementations require a large volume capacity in the vacuum pumps. There are ways to reduce the need for volume but without a context here it is hard to say how effective they would be.
    I'd love to see pics of your setup.
    Sadly no work pictures are allowed! However we have a pretty large selection of systems at work producing vacuum. These include FASt pumps of several designs, Roots blowers, Varian and other high vacuum systems pumps, venturi generators, some german pumps of which i forgot the brand and a variety of other one offs.

    Probably the pumps most suitable for this usage, that we have at work, are the GAST pumps (various types) and the Roots blowers. Even though they can work well for small things id avoid venturi generators relying on compressed air as the efficiency sucks. If you have a small job, with low leakage, a small vacuum pump will do.

    If it sounds like there are a lit of "IFs" above it is because what is suitable depends so much upon what is being done.

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