Re: [CAD_CAM_EDM_DRO] Re: Z axis

My comments interspersed.

>>Matthew:
> > Without having to do the math I wonder how much torque a guy needs
> > so he wouldn't have to gear down (slow down) the z axis drive.
> > The mill is new and without any wear.

I mounted my EMC's Z-axis drive through the right-hand side of the knee.
(Cut a hole, built a bracket) My servos are 90in/lb, 3/4" belt drive, no
reduction. Acceleration is good. But....

> Jon Elson's comments:
> I think it is unreasonable to try to CNC the knee without a ballscrew
> retrofit. And, after a ballscrew, you'd need a safety brake to prevent
> the table from dropping when you go to E-stop, or lose power. A
> reliable counterbalance, either weights and pulleys or gas springs,
> would help out, but then you'd definitely need a ballscrew, or the
> backlash would show up, without the knee weight.

I have a ballscrew on the Z, and yes, it drops like a rock when e-stop is
pressed. (counter-balance air cylinder is being fitted...) Bridgeport II's
use the air type of balance. The air cylinder counter-balance also controls
the rate of descent when e-stop is hit. The table has to be manually locked
in place when power is off. Note that a counterweight wouldn't control the
accelerating rate of descent.

Might also add that the machine is using iron from a Moog adaptation of a
Bridgport 1, so the
knee/saddle combo is quite a bit heavier than the Bridgeport's. (the saddle
is non standard - 42" wide, box-way'd to knee.)

- Keith





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