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Author Topic: Ditching the Vacuum Hold Down  (Read 1988 times)

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Ditching the Vacuum Hold Down
« on: February 01, 2016, 06:25:44 AM »
Hey guys, I am going to be cutting out some dog cutouts for a customer out of 3/4" plywood (11 or 12 ply birch).  The dog measures 14x10.5".  I'm also looking at cutting out smaller parts.  So I'm told that below a certain surface area, vacuum cannot hold down small parts due to atmospheric pressure.  Two questions:

Does this include a dedicated spoilboard with gasketing where the vacuum will not be opened up at all after the cut process?

The other idea is to ditch vacuum altogether and onion skin the parts, rip the plywood into 2' x 8' sheets, and send through a drum sander to dislodge the small parts.  I know the part will be thinner but this dimension does not matter to my customer at all.  Has anyone ever tried this?  I wouldn't have to set up a dedicated spoilboard for each job if I did this.

Thank you in advance!

Offline Tweakie.CNC

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Re: Ditching the Vacuum Hold Down
« Reply #1 on: February 01, 2016, 07:15:57 AM »
If you have a perfect vacuum then the hold-down pressure is 14.696 p.s.i. If you are only holding on small areas of the work (to enable cutting- through) then, I think, you can calculate the requirements.
I use a vacuum table for small engraving jobs but I never use it for cutting through ( including pcb hole drilling ) but when it does come to cutting through, I ditch the vacuum table and double sided sticky tape becomes my best friend.

I must admit I do like the idea of onion skinning and sanding free but why not just use tabs ( created in the CAD/CAM ) and then break free ??

Re: Ditching the Vacuum Hold Down
« Reply #2 on: February 01, 2016, 07:29:31 AM »
The part would be completely done after the onion skinning.  I've used tabs before, but then there's the manual sanding after the fact to get rid of the tab.  This job is 300 dog cutouts.  As for other parts, I'm hoping for much higher quantities.  Just trying to automate as much as possible.

Offline ger21

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Re: Ditching the Vacuum Hold Down
« Reply #3 on: February 01, 2016, 07:42:06 AM »
The dedicated spoilboard with gasket should work, if you have enough vacuum. It also depends on the tool size you're using, and how fast your cutting. If you're cutting with a 1/2" bit in one pass, it probably won't work. But a 1/4" bit in 3 passes will.

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