What kind of valve?

[chipmaker4130]

Maybe you are already aware but air moves fast when it goes. It might be junk fast if you get your finger under it. Hydraulic can be controlled. Much safer.

Air can be controlled too. We use simple orifice restrictors to get the desired rate. They don't change the ultimate pressure/clamping force, just the rate at which it is achieved. It also gives you a fraction of a second to get yourself out of a 'pinch' before real pressure builds.

edit: oops, I see BF already mentioned the damping effect!

[welderskelter]

I am not real familiar with using air for this sort of thing I guess. I do know where I have seen it used it was used to control valves that needed speed. Glad to see there is a way to control it.

[chipmaker4130]

. . .Don't put the throttle on the air line that closes the clamp. . .

Why not? Our equipment is metered on the input which provides a very stable, slower action. With the restrictor on the outlet you'd get a fast initial move that isn't dampened until the pressure rises in the backside to nearer the input pressure.