Re: faster steppers

Ian,

Stepper motors NEED the damping of an attached load... This is one of
the things that led to the development of microstepping ,which was
originally pursued to reduce/eliminate resonances RATHER than to
increase resolution. The electronic processing/manufacturing industry
drove this by making machines which presented little load to the
motor... Also the need for optics(controlled by steppers) to
not "wiggle".

The rotor magnet/coil combination inside the stepper has overshoot
and settling during its' operation (since it is a magnetic FIELD that
is doing the pushing/pulling; no defined machanical link). This is
known as "ringing". Look at it on a scope and it looks similar to the
output from a ringing bell.

The stepper is is busily "spring-stepping" its way around (dancing if
you will), and sometimes isn't done (getting to position) before the
next pulse says to move again. Think of a human dancer that has no
rhythm, and how they don't "keep up with" the music. Ever notice how
these "guys" are often flailing about?

Now, give that poor dancer a partner, who takes hold of his hands
and 'calms' the situation. That's what the load on the shaft of a
stepper does! It reduces the "flailing about" by reducing the time
spent settling into each commanded position, so the motor keeps up
with the "music"!

There are fluid filled disks (called Lanchester dampers) which are
used even WITH some types of connected machines. They have the same
calming effect as the dance partner...

Hope this helps.

Ballendo

P.S. So get your motors hooked up to the machine before trying to
solve the "top speed" problem...

P.P.S. What control software are you using?

> I don't have much load on the motor(s) at the moment as I only have

one slide finished and the other two motors are running in fresh air.
The one slide I do have working is running on steel balls and so
doesn't have much friction.<snip>

> Ian