Re: [CAD_CAM_EDM_DRO] uh, Mariss, can you clear up my confusion ?

> Since I want to drive a 120 inch long lead screw,
> am I screwed ? that is roughly 12 minutes for a
> 10 ft travel. or if use a 0.9 deg per step,
> that would double to just over 23 minutes.
> now that is truly agonizing !

One thing you should do is use a coarse pitch screw - you won't gain
anything in terms of mechanical advnatage with a fine pitch (sliding
contact) screw, so keep the pitch coarse.

> How fast can you spin a servo ?

FAST - basically as fast as the fastest electric motor (of any chosen
style compatible with your amplifier) that you can find - I would
imagine 8 to 10 thousand RPM is do-able with readily available parts.
You will need to make sure your encoder count frequency is within
allowable limits and if the loop is not high performance you may need
to program a generous acceleration ramp, but you should be able to get
it going very fast. Realize that at high speeds a shaft like that
will start to whip even if very carefully supported - sometimes they
actually rotate the nut rather than the shaft because of this! Also
consider if a cable or open timing belt drive would work in your
application instead of a screw.

Chris Stratton

-------------------------------------------------
Christopher C. Stratton
Engineer, Instrument Maker, and Horn Player
ccs@... 617 628 1062
http://web.mit.edu/~stratton/www/brassbuild.html