Vacuum Table - Does it suck?

I originally made a jig for a work piece, but it turns out that it won’t work for my purposes. I decided to go all out and make a vacuum table instead. The plan is to use a combination of vacuum and dowel pins (and maybe some double sided woodworkers tape) to keep the workpiece in place.

Instead of making a small vacuum table for my work piece, I decided to make something that fits almost the entire table of my HDM - 18 x 24". If I pull it off, it’ll let me machine four pieces together, reducing the number of tool changes, etc.

The table uses 5mm holes for the vacuum. There are about 1,000 such holes. They are split into eight different zones, which are each connected to high pressure hose. The eight hoses eventually come together via splitters into one large 1 ¼" hose, which is then stepped up to my 4" dust collection hose. The dust collector also goes to the HDM for dust collection. If there isn’t enough vacuum generated since it is also dust collecting, I can always connect it to my shop vac.

The vacuum table will be directly bolted to the CNC table (see images - those are the 15 large holes). I see the HDM uses M6 bolts, so I’ll machine these just a bit larger than 6 mm diameter (6.1?).

The aluminum plate is 24 x 18 and 0.5" thick. I’ll machine eight zones for vacuum under it to go to the 5mm holes in the zone. The channel for this will be about ¼" thick, and the open area under the 5mm vacuum holes will be as long / wide as it needs to be, but also about ¼" open. Under the ½" plate will be a much thinner 0.1" aluminum plate to close up the channels and prevent leaks. On top of the vacuum table will be ⅛ or ¼ inch plywood for the spoil board. All three of these will be bolted together, and directly to the CNC table.

I have some questions!

  • Are the 5mm holes enough to generate the vacuum? Each work piece will have about 200 such holes under it.
  • Any comments on the eight separate zones? They are all independently valved, so I can shut off zones not being used.
  • Is the ¼" channel for each zone too small? Am I going to run into poor airflow issues with this?
  • Can I use some silicone between the bottom aluminum plate and top aluminum plate to help with sealing? Should I use a thin rubber layer instead?
  • Any tips from the experts on machining this behemoth on the HDM?

Thanks!

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hi, I’m no expert but the think the vacuum suction is different with from an actual suction table … i have a 4x8 cnc i use a 4x8 sheet of mdf for my spoil board with no holes in it … i think with all those holes u will lose suction

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I was concerned about that too, which is why I set them up into eight separate zones. Each individual hole can be plugged also if necessary. I’m about to start cutting up a giant 2x2’ aluminum plate… curious to see how it will hold up!

I suggested in an earlier reply using the size hole you were drilling to about half way through the aluminum block, then drilling a much smaller size in the middle of that. The vacuum holding capability is relative to the size of the hole underneath the work, but you don’t really need to have a high volume of vacuum. By using the smaller through holes, you lose less volume of air for those that are uncovered. It takes a slightly longer time to build the full suction against the work due to the decrease in the volume of air being evacuated from each hole, but it isn’t significant.

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I missed that - thanks. I think that is a good idea. I may drill a test plate to see how it all works before using the giant piece of aluminum.