Re: SLO-SYN 12.7 Amp motors

> From: Charles Hopkins <chopkins@...>
>
> I have a Bridgeport which has been fitted with SLO-SYN 1.75 volt 12.7 amp

stepper motors on all three axis.

>
> They are 200 steps/rev and set at 1 to 1 ratio to the ball screws
>
> How much power supply do I need to drive these motors and where can I buy

them.

>
> I also need drivers which will interface with EMC software.
>
> I have the machine with motors mounted and I have a 166 MHz computer with

EMC loaded. I need everything in between!

>
> I have the old power supplies, but I think an upgrade is warranted here.

1. First take a look at this page:
http://users.erols.com/mshaver/bps1.htm

2. I'm going to agree with Darrell on two points:

a. Microkinetics DR8010 drivers (There's a link to these on the above page.)

b. Keep the original power supplies for now. I bought supplies from
Microkinetics, but my machine came to me totally stripped. There might be
some advantage to Microkinetics' 72 Volts versus Bridgeport's 56 Volts, but
it's worth trying to save the original supplies.

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