[Joz]

Hi, I know nothing about how vacuum tables work so bear with me. I'm trying to work out how to make a vacuum table for my cnc router. I want to make several pods with foam seals around the edges. Is it the general procedure to have the work piece attached directly to the pod? Is so how do you get round the problem of "overcut" where the cutter cuts deeper than the material and into the foam seal? Or it just a case of setting the Z height really carefully so it doesn't machine through the stock, or do you use a spoil board? But if you use a spoil board then you've got to use double sided tape or something to hold the work piece to the spoil board, but doesn't this defeat the object of using a vacuum table?
Also I was watching a video from Laguna CNC about their CNC vacuum tables- they seemed to infer that the MDF spoil board on top of the vacuum is porous enough to let suction through so you can just lay the work piece on the spoil board and it will hold- is this right?

Any help gratefully received
thanks
Joz

[ger21]

There are basically two types of vacuum systems.
One uses pods, or a non porous bed with a rubber seal. With these types of systems, you can NOT cut through the material without damaging the pods or table. You either need to make custom size pods or position them so they won't be cut.
The second type pulls vacuum through the MDF spoilboard, so you can cut through the material into the spoilboard. Not that as the spoilboard gets more and more cuts in it, the holding power will decrease from leakage through the cuts, and the spoilboard may need to be resurfaced quite often. This type of system typically needs a much higher CFM pump than a pod type system. While a pod system can work with 2-3CFM (depending on the porosity of the workpiece), a flow through table can requires 150-300CFM to work well.