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.  |