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View Full Version : How is this chuck actuated?



atomarc
10-11-2013, 04:49 PM
I have enclosed a link to a YouTube video of a machine with what I'll assume to be a air actuated chuck. It's a 'thru' chuck so if it is indeed air actuated it must have some type of rotary ring union to supply the air for clamping that allows it to turn and offers the 'thru' feature as well.

I want to figure out how this is done or define the name of the rotary air union so I can start a intelligent search for info. Anyone have a clue where to start? I don't care about the particular machine shown in the video, only about the concept of supplying air to a rotating, hollow spindle assembly. I would prefer not to build one but to find one made already...it's for a machine I may be building.

https://www.youtube.com/watch?v=hkCh6lk-NhU

Stuart

winchman
10-11-2013, 05:20 PM
The spindle always stops with the cylinder at the very top. If a heavy spring is used to clamp the wood, air only needs to be supplied to the cylinder at one place to push the chuck open. That could be accomplished with something much simpler than a rotary coupling several inches in diameter. All you need to do is line up two holes, give it a shot of air, and press on.

atomarc
10-11-2013, 06:02 PM
Didn't notice that, not less think of it..good observation. I think the only problem in my mind it that it would be much more involved to get the chuck to stop in the exact same place every time unless one were to move up to steppers or servos and a PLC. This seems more complicated than making a rotary ring seal of some sort. CNC lathes and machining centers do this regularly, but again that's getting out of my comfort zone.

Stuart

M_C
10-11-2013, 06:30 PM
You can get through hole actuators for CNC lathes that use rotary unions, however the lathe in that video would require quite a substantially sized rotary union. It is possible it does use a rotary union, as it doesn't seem to be capable of spinning that fast so surface speed of the seals might not to be too much of an issue.

It may use some form of alignment as winchman suggests, however I suspect the reason it always stops there is for easy loading, so you can lay the square into the fixed jaw. It looks like the machine in the vid has a servo spindle, so precision alignment is pretty easy.

Rustybolt
10-11-2013, 08:54 PM
Hardinge Bros. used to use air chucks on their chuckers and early CNC machines. It worked pretty well. You might want to start there. For a mechanical solution check out how an automatic screw machine actuates its collets.