Re: SLA7062 Sync Mode (was New Article bla bla)

Hi,
The 7062 chip provides a very imporant signal for those that want
to change step modes (or sync, etc.) "on-the-fly". This is the MO
(HOME) output. It is active when the drive is commanding the motors
to 70.7 each phase. From this position, you can switch to any
stepping mode you want, as long as the controller issuing the steps
keeps track of the scale factor and steps issued. You can also turn
on synchronous mode if the signal is active.

If you have an intelligent controller/step generator (not just
drive), and a mechanical system with more than 8 microsteps of
backlash (assuming running in 1/16th step mode), you could
concievably move the motor within the backlash area to a HOME
position, then set the SYNC on, during power down or inactive times.
Upon reactivation, sync would be de-activated, the steps added to get
to HOME would be removed (they would not move the machine since they
were added in the backlash range), and once this is done, start
machining again.

Jeff


--- In CAD_CAM_EDM_DRO@yahoogroups.com, "turbulatordude"
<dave_mucha@...> wrote:

>
>
> > I've always heard that microstepping (anything higher than
> > half-stepping) does not improve positional accuracy, it only

serves to

> > reduce mid-band resonance by smoothing out the step impulses.

The

> > holding torque at microstep positions is very low, and the actual
> > position is not linear, so even in very lightly loaded conditions

it is

> > necessary to carefully profile each stepper to map the position

of the

> > motor at microstep positions.
>
> The concern is that when running in microstepping mode and then
> changing modes for no mechanical reason, you *might* jump to the
> nearest half step when you return (or when you exit)
>
> the extreemly rare possibility is that each and every occurance will
> be in one direction.
>
> *IF* every departure were on the same direction, *then* you *might*
> see some accumulative errors.
>
> Sounds like empirical testing is in order.
>
> Dave
>