What am I looking at here? Power drawbar? Something else pneumatic?

[Surgo]

I recently bought a new-to-me CNC milling machine. Ancient 3hp Millport from the 90s, with a correspondingly ancient controller (Anilam 1100, complete with a vintage 486). It boots! The servos work! But there's a mystery object on the side that I can't figure out. I thought it was a power drawbar, but it doesn't look like any power drawbar I've ever heard of.

There's what seems to be an air-solenoid valve in the back. Its power cables go back to the controller circuitry, but I haven't been able to find anything in the documentation for the controller on actually tripping it. You can see the solenoid in the second picture. Two air lines come up from the valve up the side of the machine, to the head, in the first picture.

There's a bunch of scratches on the machine that show that the air in that tube pushes on a lever that swings up and down. For what purpose, I'm not sure. Does anyone know what I'm looking at here? Like I said I thought it was a power drawbar, because there's no other nut or twist mechanism on the top of the head for operating the drawbar. But I don't see how this would work, and there's absolutely nothing in the controller that I can find for operating such a drawbar. So I have no idea what this is.

 

[john.k]

Its possibly a spindle brake............maybe added in after an incident...........did the P/O have all his fingers.?....EDIT.....go through the electronics looking for caps with problems like bulged ends,or leaks,replace them ,and it will be quite reliable...

 

[Bob Korves]

You are probably looking at a two direction air flow control valve. It is probably sending air in alternating directions to an air powered draw bar motor.

 

[Surgo]

Its possibly a spindle brake............maybe added in after an incident...........did the P/O have all his fingers.?

Ooh, good thinking! It's in exactly the right place for a spindle brake too. That would also answer why it goes to the controller. Once I have daylight I'll open up the saddlebag and try to trace where the wire goes.

While I'm at it I'll also take a look at the top and try to figure out "how the heck do I operate this drawbar?!".

You are probably looking at a two direction air flow control valve. It is probably sending air in alternating directions to an air powered draw bar motor.

The one part of that that confuses me is -- where would the motor be housed? I don't see anything external for it. Would it be in the head?

 

[Bob Korves]

It would fit the top of the spindle, just like on a manual mill. It looks to be pretty shallow/short for a drawbar motor, but the hoses are going to the correct place for one. I assume that mill does not have automatic tool changing, so the fact that it goes to the controller might be a brake. Still, the program may tighten the drawbar at the start of an operation, and loosen the drawbar at the end of the operation. That would be helpful and would save a lot of time...

 

[Surgo]

Just in case anyone ever comes back to this with a similar question: it was, in fact, a spindle brake. Verified manually by turning the spindle on, then off, then pulling the brake by hand.

 

[P. Waller]

4 way solenoid pneumatic valve.
The copper plumbing on the "bottom" is the input, the fittings on either side are mufflers/flow controls in the exhaust ports.
The 2 ports on "top" control the device that it operates. Having only one solenoid leads me to suspect that it is 2 position and likely not a power drawbar control.

I could be completely wrong however, pneumatic logic circuits take many forms

 

[derf]

Even power drawbars have one input to the control valve. The control valve will determine the direction depending one which way you rock the switch. I don't see a power drawbar on that machine. There should also be a bypass switch for the spindle brake.