I am getting tired of tabs, double-sided tape, and other tedious forms of workholding, so I’ve been thinking about converting my Woodworker QCW into a vacuum table. It’s shaping up to be quite an investment, so I figure I’d post my plans here first and open it up for others to critique, point out any potential shortcomings, help over-engineer, or just copy for themselves.
This plan will involve making 3 vacuum zones that can be turned on or off individually. The business end is currently a 3.5 CFM oil-free vacuum pump. I have no idea if this will be sufficient for CNC vacuum chucking, but it is similar to what AirWeights includes in their prefab 24x24" kit.
Please take a look and let me know where I can improve.
Sorry about the screenshot of links - could not figure out how to embed a table.
Plenum on QCW:
Here, each main panel of the QCW is a distinct vacuum zone, that can be turned on or off with a valve at the pump. This grid consists of 1/4" channels, which will be sealed with lacquer or another sealant. There will be square gasket cord that sits 1/16" proud of the channels to line the perimeters of each zone. The threaded vacuum harness is fed through the ports and held in place with gasket locknuts on either side - the harness will sit just below the underside of the QCW.
Spoilboard on top of plenum:
On top of the plenum, there will be a bleedboard - 1/2" MDF surfaced on both sides for permiability, then lined with tile gasket on top, and finally bolted into the QCW t track with countersunk hardware. The tile gasket is supposed to reduce leakage by focussing the vacuum to a grid of holes, provide a bit of cushion to compensate for an imperfect workpiece surface (i.e. act as another gasket), and finally provide some additional lateral friction for workholding. Seems to work well based on videos I’ve seen. The edges of the MDF will also be sealed with lacquer.
Vacuum harness diagram:
I like your overall design - seems well thought out to me. Considering doing something very similar to my machine. Plumbing will be slightly different as I plan to use ‘push-to-connect’ style. I’ve tested it and it’s good. Also very easy to reconfigure - no tools necessary to connect/disconnect. Looks like you picked out a nice pump! I going cheap for the pump during the onset of this experiment. I figure I can always sell it in lieu of a nicer one if I need to go that way. I heard about the oil filled pumps (like the one I ordered) getting hot and making a mess so the caution flag is up! Haha! Hopefully I won’t be running it long enough to get hot - so far, I’m just cutting out pickguards for guitars…
did you ever get around to making this a reality? i would love to duplicate it if so!
Not yet! I recently moved and found out that I need an electrician before getting back in the saddle. Other priorities have kept me busy. Let me know if you beat me to it - I’m happy to share vector files if they would help (haven’t made tool paths yet).
oh yes! that’d be awesome
This is a really nice and well thought out design. If I can make one fundamental suggestion it’s to get a higher CFM pump. 3.5 will likely work OK for the area (24”x24”) shown, but if you can get to 5+ you’ll have more options open to you and less potential insanity chasing small leaks. If you miss any sealing surfaces with the lacquer (or other sealer), the plenum junctions, etc… you’ll have more flow rate to overcome small leaks and maintain a decent vacuum level.
One other thing to keep in mind are the gaps for your T-track in the QCW. It may be worth sealing off the opposing strips on the underside of the “bleedboard” with lacquer also, especially if you’re sticking with the 3.5 CFM pump.
You may also need a T-fitting in each airline in the diagram shown since you have 2 ports in each individual plenum. If you’re looking to save on fittings, plastic barbs also work well with the braided hose shown at a fraction of the cost.
Looks like you’re going to get a great result with careful attention to sealing. Nice work!
toiyabe_vacuum_qcw_files.ai (1.2 MB)
Here is the .ai vector file for anyone who wishes to play with this. It’s a bit rough, but hopefully the layer names are intuitive enough.
Note that the front left “port” is currently in a position that would not allow mounting of a controller or PSU box under the QCW. Either the ports or box will need to be flipped to the rear.
Thanks! I originally wanted the smaller pump for the lower amp draw, but it turns out that the vendor mentioned has a 5 CFM pump at nearly the same draw. Regardless, it looks like I am putting in a circuit or two in my new garage. Hopefully I can tackle this sometime this winter.