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Thread: CNC Vacuum Table advice

  1. #1
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    Default CNC Vacuum Table advice

    I know a few people on here do machining so was just wondering if anyone could offer any advice

    been trying to do a vacuum table setup but an failing badly.

    I purchased this -

    http://www.ebay.co.uk/itm/CNC-Vacuum...item487aa50799

    and today I got the uni-jet 75

    http://www.cattaniesam.co.uk/suction...ry/uni-jet-75/

    the guy from ebay recommends 3cfm, if I worked it out correctly the uni-jet does 1250L/min which is 44cfm. so in theory plenty of suck.

    got a 32mm pipe coming out of the vacuum pump, then just before the table reduced down to 10mm as that's what you need to plug into the vacuum table. length of pipe maybe 2 metres

    when on and you try to move the work piece with your hand, you can but its bloody hard, its stuck down pretty dam well. you have to really really force it to get it to move with your hand. but when trying to machine it, it seems to move so easily.
    I'm using a 6mm cutter, with a z depth of -0.5mm with a feed rate of 30mm/min

    anyone got any advice?
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  2. #2
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    ... you have to close all pin-holes, not covered by the part to fix it -- and ensure, the part bottom is flat enough to seal his area.

    The other part is the relation between the holding force vs. the machining force, what's defined by bottom size, part height and forces while milling ... the smaller the millbit diameter, the better this relation ...

    Viktor

  3. #3
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    The table states the pump needs to go down to 10Pa (Suggested vacuum pump min Vacuum Pump 84l - 3cfm / 10Pa); in my experience, those type of pumps go down to about -0.7bar which is 300KPa, so you're a country mile off achieving sufficient vacuum.

  4. #4
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    so it would seem
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  5. #5
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    would one of these work?

    not sure how to work out if they have enough vacuum

    http://www.clampusystems.com/Venturi.html
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  6. #6
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    Hi Andy, ....Not really my area of expertise () ... but quick answer is ...NOT A HOPE IN HELL !
    You will need a proper vacuum pump not a venturi !

    GAST also make cheap vacuum pumps but you need to throw the spec at NobleGas to check whether any GAST models will be enough...... You are looking for low pressure NOT high flow rate !

    Cheers

  7. #7
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    ok thanks .
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  8. #8
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    I have seen people use a venturi on a vac table. Problem is it needs like 25CFM to work. That is a huge compressor!

    I have a GAST 0322 vane pump on my pattern router. I think its rated at 25" Mg. I can tell you this: I can cut 3/8 of an inch in 3/4 baltic birch in one pass as long as the part is over say 80sq inches. I can cut 1/4 inch think abs plastic in one pass removing about 1/4 inch or so with a 9sqin part.

  9. #9
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    (no idea what any of them numbers mean, I don't get inches at all)

    wood and plastic are very different to aluminium.

    I'm looking to machine like 250mm by 160mm by 5mm thick ally plate with a 6mm cutter.
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  10. #10
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    One inch = 2.54centimetres .... but I think woody meant 25" HG - which would mean that it lifts that amount of Mercury ... but that probly doesn't help much....gonna have to wait for someone who cuts ally!
    Cheers
    PS. The GAST vane pump was the one I was referring to, but whether it's enough or not .....dunno !

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