Re: SLO-SYN 12.7 Amp motors

The "jitter" problem should not be to hard for the Bridgeport because even
at half stepping maximum step rate at rapid would only be 3200 -3600 steps
per second so you should be able to slow the timing down and not stress the
RT system.
Darrell

----- Original Message -----
From: Matt Shaver <mshaver@...>
> 3. Darrell also said, "I think the main thing in using these drivers is
> getting the timing correct in EMC." This is something I have yet to be
able
> to do, and is a problem that Fred has been working on for some time now.
> Without going into all the details the problem is that there is a some
jitter
> in the step output of the EMC. Generating the step pulses stresses the
real
> time part of the software considerably and much work has been going on to
> reduce the jitter. Ahha (and Flashcut also) uses external hardware to
avoid
> this problem, but I am reluctant to adopt that approach until the
"software
> only" approach has been thoroughly developed. Other "software only"
solutions
> avoid the problem by going into a tight loop in their program with only
> periodic polling of the keyboard buffer to check user input. This option
is
> unavailable to us as we want to multiprocess and keep Xwindows alive, etc.
> The problem comes in when you try to control a large machine (like a
> Bridgeport) at high speeds (60+ inches/minute or thereabouts). Since the
> torque output of stepper motors drops with speed, any timing variations in
> the step rate (at high speed) can lead into resonance problems or
stalling.
> Fred has made some good progress lately and will have an improved version
of
> the stepper software available in the near future.
>
> Matt
>
>
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