Hello,

I'm trying to understand how these work specifically with a CNC router. Is a sacrificial board used underneath the work piece, and if so, how is the vacuum transferred through it? Or is the work piece just placed straight on to the table? For some reason, I just can't get my head around how it functions. I come from a screen-printing background, so I understand the principal of the vacuum holding things down - it's just the mechanics in between I'm unsure of.

Thank you!

GVP.

There are different types of vacuum tables. On a lot of commercial routers, they use very high volume pumps that suck through a sacrificial sheet of low density MDF. You can also make jigs or fixtures that use a foam seal to contain the vacuum. Or make individual pods with foam seals which support the work above the table. The last 2 options usually require passages or vacuum lines attached to the jigs. A great place to get gasket foams and non slip rubber for jigs and fixtures is www.allstaradhesives.com

And to add to what Gerry said, if your cutting all the way through the work you would want a sacrificial board ( or at least a dedicated fixture) under the work so you don't cut into the table. If your not going all the way through the material you don't have to use one(at least if you can get some kind of seal between the work and the table). Although I like to have something between the work and the table even if im not planning on cutting all the way through. Just incase I make some kind of mistake, It gives me extra time to catch it so I don't damage the table.

I use a machine that uses a vacuum table. It can suck through up to 50mm MDF. We use a sheet of either 9 or 12mm MDF underneath as a sacrificial sheet so as not to wreck the table. We keep skimming the sheet til it gets to around 2-3mm thick and then chuck it. You will have to flip the sheet too other wise it will cup and won't suck to the table. You have a table made up that is usually squared with a couple large holes for the vacuum pipes. In the middel and towards the outside edges is some foam rubber which is used as a seal so that the vacuum doesn't escape. Once a sheet of MDF is on there and the vacuum is on it won't budge unless there isa hole in the rubber somwhere allowing the vacuum to escape. The other type that I have seen is the pod vacuums. You can move these around to the position you need it and then place your material directly on them. You usually can't cut through the material on these unless you move the pods in specific locations so the cutter will miss them. Some CNCs will move them according to the size and shape of the material to be routered. They don't have a sacrificial material put on them because from what I know is that the suction isn't great enough to pass through the sacrificial and suck down on top. One thing to watch when using a vacuum table when a piece gets to small the machine will quite often kick it off unless you make a final pass of half a mm or so or you just leave a half a mm still attached and hand route it when the machine has stopped running.

We manufacture vacuum fixturing. Check out our website, there are videos to show how our products work.
www.nemi.com

hi

there is another company called witte from germany .. these people make excellent vacuum tables for a variety of applications.. perticularlky their vacmat system can help you machine through.

Please go through their website http://www.horst-witte.com/

dhiruj