vacuum powered clamp

[tkovacs]

I need to cut a hundred or so 7"x24"x3/4" red cedar deck railing parts.
My vacuum table was not designed with mechanical clamping in mind - probably something I would think about in the next version.

This idea has been in my head for some time and I thought it would be a good time to give it a try.

Jumping to the (I think) final solution here is what I came up with:

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This shows two of the pieces clamped in place at each end by a shop made vacuum powered clamp.

These are really simple to make. Here is the prototype:

as it would be used:

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and from the bottom:

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It is simply a piece of 3/4" MDF with the center cut out with a 1/4 in bit.
The membrane is stuck to the top outside edge of the mdf with two sided tape. The clamping paddle is screwed to the center "puck" through the membrane. There is enough flex in the membrane to raise the clamp face (the overhang of the paddle) about 1/8". To hold down a 3/4" piece with this prototype you would need to add a bit of 1/16" padding between the clamp face and the piece and turn on the vacuum. The membrane is simply some plastic shelf liner.

On the production piece I added a 1/8" strip of maple as a return spring:

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A few pounds/square inch over ~100 square inches goes a long way.
These pieces cannot be moved by hand once the vacuum is on.

[myxpykalix]

Terry,
This is just me, but i don't understand how your clamp works. Do you have any other pictures and could you explain it more in detail because i just don't understand how it works.....thanks

[rb99]

I don't get it as well. I am in good company though.

RIB

[knight_toolworks]

good idea. but me I am lazy I would use my nailgun to hold the boards in place and use a downcut bit to cut them. the sawdust would hold the piece in place and nailing is fast.

[navigator7]

Its a custom fixture used to hold specific pieces...like a run of 100?
The cantilevered boards hold down the parts you are cutting?

[tkovacs]

Sorry for the poor explanation. Maybe this will help.

Take a 6"x6" square of 3/4" MDF and route a 4x4" square out of the center.

Make a drum by fixing a membrane over the top.

Place the drum, membrane side up, on your vacuum table and turn the power on. The membrane will get pulled toward the table with (in my case) ~4 psi.

We get 4" x 4"x 4 psi = 64 pounds of force to work with.

Now return the 4" square center piece to is original position underneath the drum head, place second piece of MDF over the top of the drumhead and screw this to the center piece through the membrane. Allow for the top piece of MDF to overhang the original 6" square and that overhang becomes your clamp face.

Here is one more pic that shows a closeup of the clamp face open (top) and under vacuum (bottom):

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