RE: [CAD_CAM_EDM_DRO] What ratio to use for stepper motor drive?

I'm using 1150 in-lb motors at 1000 steps per rev, driven by 72V, 10A
microstepping drivers. My drivers scale the current with the pulse rate.
The machine is a big knee mill. I started with 1:1 ratio and later switched
to 1:2 reduction, giving me .0001 resolution.

This resolution is not really useful on a knee mill, but it makes for
incredibly smooth movement. The common misconception is that microstepping
is used to increase resolution. The intermediate steps are generated with
sine/cosine current ratios between phases, but the rotor angle does not
necessarily follow this function accurately. The real advantage of
microstepping is reduction of resonance problems.

Assuming you have adequate motors, the determining factor is your drivers.
I will confer with Jon that voltage is what you need for speed. You won't
get sufficient current rise at high speed if your drivers can't supply the
voltage. I get away with 1:2 reduction because I have 72V supplies. I
still get reliable jogging at 100 ipm.

So I guess it comes down to what you are working with.

Doug

> -----Original Message-----
> From: Bryan Mumford [SMTP:bryan@...]
> Sent: Wednesday, April 26, 2000 10:17 PM
> To: CAD_CAM_EDM_DRO@egroups.com
> Subject: Re: [CAD_CAM_EDM_DRO] What ratio to use for stepper motor
> drive?
>
> Perhaps I should have asked my question in a different manner. What
> I'm curious about is what ratios people are using. I'm using 1:1 and
> it gives me more resolution than I need and less torque than I want.
> What ratios are other people using in their stepper motor linkages?
>
>
> >Divide the number of steps per second by the number of step per
> revolution.
> >That will give you the speed in revolutions per second. The multiple time
> 60
> >for RPM
>
>
> Bryan Mumford
> Santa Barbara, California
> http://www.bmumford.com
>
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