On 2010-07-09, Karl Townsend wrote:

I could never get it to run at super slow speed in voltage mode, but
could easily do so in tach mode. It was kind of nice to see.

Disclaimer:My control uses a Galil dedicted real time controller so your
results may differ.

Torque mode is the preferred mode for most all applications, certainly for
what you're doing. Precise smooth control is not an issue at all with lathe
and mill applications.

The place where this is most likely to make a difference is
cutting a line which almost but not quite parallels an axis of the
machine. This means that one axis is moving at a speed which is
determined by the appropriate feed rate for the tool/material
combination, and the other axis is moving at a very slow creep. An
example would be turning (or milling) a shallow taper. While turning,
maybe Morse, even more so for the taper of a tapered arbor.

If the controller is monitoring the encoders frequently enough,
and the encoders have sufficient resolution, you are fine anyway.
However, with a coarser resolution encoder, the ability to command a
precise slow speed means that you can trust it to maintain the very
shallow angle between encoder pulses. The Galil, with a set of
sufficient resolution encoders probably does not truly need the tach
feedback -- but even it might find the job easier with that.

Enjoy,
DoN.

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