Re: [CAD_CAM_EDM_DRO] More Questions on Z-Axis Drive

Vince Negrete wrote:

>Sorry to repeat but I guess I asked my questions using Jakes subject line.
>(duh!)
>
>I'll probably have a similar issue to the one Jake has with his Z-Axis.
>(and yes Jake, My mill also has a clunking noise going down below a
>certain point)
>
>

Well, this is a killer. You can't machine anything accurately with the
knee bouncing up and down
like that. It might even rock the knee enough to break small drill bits
or end mills. You may have
to check to see that lube is getting all the way into the slides, or
switch to better lubes. Mine used to
do this, too, until I switched to way lube.

>The question I have for the group is: How big a Servo/Stepper motor do you
>recommend for the Knee? oz/inch ? Anyone? Mine is sort of tough to
>turn. (about 15 pounds roughly) Well oiled but I think just heavy, damned
>heavy in fact... Could I go 4:1 or 6:1 on the pully?
>

Sure, a servo motor usually has lots of speed. If you can dig up a big
fish scale, you can determine
the actual torque needed. Multiply pull on scale (measured in Lbs)
times radius of the crank (inches)
and you have In-Lbs. Multiply that by 16 and you have in-Oz. Probably
would be good to multiply
by 1.5 or 2 to give some headroom for acceleration.

>If I build the larger pully to do it will it have problems with the
>stepping software. (ie: Maximum Steps for a distance) Is there a limit in
>EMC settings, say for a maximum pully size??
>
>

EMC has no limits, other than how many step pulses it can put out per
second. If you need more
pulses per second, you can get a faster CPU.

Jon