Re: [CAD_CAM_EDM_DRO] Servo torque test question

> Hi all,
> After having very little luck finding someone in this group
> that has applied Gecko g320/340 drives to a mill the size of
> mine I have decided to try and size servo motors that will
> work on my mill. The question I have first is, can torque
> required to run an axis be determined relatively accurately
> with a string around a drum attached to the lead screw and a
> spring scale pulling on the string at a fixed speed. I hope
> this isn't too dumb a question but I wanted to double check.
>
> Thanks Bob

Bob, there is a very nice servo sizing program at:
http://kmtg.kollmorgen.com/products/software_downloads/motioneering/index.ht
ml

It will calculate motor requirements after you have entered
parameters like load weights, leadscrew or gear or belt sizes
etc. It will of course pick THEIR motors but it gives the general
information as well. It is free.

Your question is a good one because frictional forces often
have to be measured. A weight or scale and string is one way. Note the
breakaway (static) friction may be different from the dynamic friction.

I think it was mentioned but a shunt wound or dc motor
can be used as a dynamometer to measure friction, mass,
and spring rates. If you have an o'scope or some data aquisition (and like
differential equations) you can measure these things and plot the polar
version of the system mechanical impedance.

I used that to calculate the friction I wanted on bearing seals
at the end of leadscrews. The seal friction terminates the screw in its
characteristic impedance to prevent large torsional resonances in long
screws.

Leslie Watts
L M Watts Furniture
Tiger, Georgia USA
http://www.rabun.net/~leswatts/wattsfurniturewp.html