Of course you can’t have a conversation about CNC vacuum tables without having one about vacuum pumps so maybe start by asking yourself a few questions. Recognize that buying a vacuum pump on price alone may sound good to the pocket book, but if it doesn't do the job then it’s wasted money.

Understanding these issues will also help you identify the characteristics that are important if you want to figure out how to build a vacuum table on your own.

How large is your vacuum table?

So we talked about the real basic version of vacuum table, where they drop down a full sheet of MDF onto a frame, to create a vacuum table. Then they pull a vacuum right through the entire MDF sheet. Obviously this is going to consume a huge volume of air to make it work. Compare that to a hobby CNC router with a small 12” x 24” table and you'll certainly understand why this might be the first question to ask yourself.

Is your table “zoned”?

Both CNC MDF suction tables and their more sophisticated cousin the aluminum “grided vacuum table” can have areas that are fed by different air lines. That way you can turn off sections of the vacuum table that are not in use, ... or use one vacuum pump to feed one section of the table and a second vacuum pump to feed the other section if it turns out that you don’t have enough suction with one vacuum pump feeding the entire area.

How large is the wood you intent to cut?

Large, heavy pieces of wood will require more holding power than cutting vinyl letters. That’s pretty obvious. Most of us don’t exactly know what the applications will be so always oversize or you'll run out of vacuum power! Been–there–done–that!

How large of a cut do you expect to make?

Obviously these last two questions are interrelated. Larger CNC router projects typically use large diameter cutters that will exert more force and require a more powerful vacuum pressure to hold everything in place.

Does your table leak?

If you are planning on pulling a vacuum through an entire sheet of MDF, will the entire surface be covered with work, or will one side be left open and be pulling a vacuum through the MDF for no purpose.. takes a lot of air to maintain a continuous vacuum when it is venting to the air! If you have a “grided” vacuum table, can zones be plugged and are the plugs 100% effective… how about the table’s composition and the plumbing fittings? Will they leak?

Does your wood leak?

How about the material you are working with. I know I can drop a vacuum right through the pores in a thin piece of red oak, so it requires more air volume than closed pore woods like hard maple. Hardwood species that like to curl before you get them locked into place will also need a stronger vacuum to prevent them from curling up and away from the vacuum clamping.

Speed of clamping:

Is it important that the clamping process is fast? Think of a swimming pool, you can fill it with the garden hose or a fire hose.. do you care which? The greater the volume of space that has to be converted from atmospheric pressure to a vacuum,  the longer it will take. If you plumb your table with 1/2” tube vs 1/4” tube you've got a lot more air to move. So the volume of air in your system and the speed at which you need to remove it, may dictate the size of vacuum pump you’re going to need.

Recognize that each one of these questions implies one of two issues.. either you need a strong vacuum, ie maximizing the 15PSI capacity of a vacuum pump and/or you need to create a huge volume of air flow. In the next section we'll add a few comments about other considerations in chosing an appropriate CNC vacuum pump. >>