Re: [CAD_CAM_EDM_DRO] Re: I am Lookig for stepper??

Mariss wrote:

> Consider this. The force (in lbs) a motor generates is:
>
> Lbs = (in-oz times 2pi times TPI) / 16
>
> or:
>
> (384 times 6.28 times 20) / 16 = 3,014 lbs.
>
> Seems to me this is just a bit of over-kill. If you mounted the axis
> vertically you could lift your average 4-door car with it.

The thing is that this is a flawed analysis, as it neglects the poor
efficiency of a sliding contact screw such as used in the sherline.
Because of this, you don't get to take advantage of the fine pitch of
the screw - you get no more force out of it than you would out of a
much coarser screw. 384 oz-in is overkill for this machine, but 150
oz-in is just about what you need to get top performance from it.
This oversimplified calculation would imply that even the 150 oz-in
motor would generate a sherline-bending 1000 lbs of force - in
practice, it won't even come close to that, but it will have just
about enough to torque left to reliably overcome the friction in the
system when the torque loss at high speed is taking into account.

Chris Stratton