Re: [CAD_CAM_EDM_DRO] Servo Dynamics 1525 servo drive noise

Thanks to everyone that responded...

Jon,
To answer most of your questions here is what I have done so far. When I
first got the machine home I installed a Advantech industrial computer with
a Galil DMC 1040 control card. Next I installed Galils servo tuning software
and Camsofts cnc software. As I tuned the servos for the new system I
noticed that Z wasn't working, so I diagnosed and found the servo amp to be
the culprit. After searching all over tarnation for the best price on a new
/ used one. I found one that was identical, except for it has the latest
revisions. (electrically the board looks a little different from the
original) After installing it I noticed that with just axis Z plugged in
there was silence. No whining noise, as with the other drives. So that's
when I started questioning the older drives. Maybe the older units just
sound this way because of the lower frequency. And the newer revised
versions have the fix for this nusense noise. Or maybe the other two are
about to fry as well. Which would make sense because there all the same age.
Anyway, the other two older drives seem to function and hold tolerance. But
it started to make me wonder if I should start looking for two more drives
to replace the others. With hardly any support coming from Servo Dynamics
this was my next best place for info.

Regards
Shawn

----- Original Message -----
From: "Jon Elson" <elson@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Tuesday, October 07, 2003 9:37 AM
Subject: Re: [CAD_CAM_EDM_DRO] Servo Dynamics 1525 servo drive noise


>
>
> shawncd2001 wrote:
>
> >I recently purchased an older Milltronics Partner mill. This
> >particular unit uses the older Servo Dynamics 1525 servo drives.
> >I have tuned the drives to where they perform the way I want them,
> >but there is an ear piercing whine or whistling sonund coming from
> >the boards. Anybody out there have the same problem? Any ideas on a
> >fix? Any information would be much appreciated.
> >
> >
> >
> Yup, these older drives have very low frequency PWM cycles, and so
> produce lots of audible tone. Looking in the book, it says it is 16 KHz.
> Most people past their 20's can't hear much up there anymore. This would
> be the same pitch as the horizontal output of a TV set.
>
> I'm wondering if what you are getting is a subharmonic or unrelated
> lower frequency than the 16 KHz? Can you make the pitch or loudness
> of the tone change by moving the axis to a different position, or
> manually damping the shafts (motor, encoder, tach) with your hands?
> Can you make a guess at the frequency of the tone? Are you sure it
> is coming from the servo amp, and not the motor?
>
> You might also disconnect or disable all but one amp at a time to see
> if it is one particular amp, or all of them emit this tone. If you can
> disconnect the velocity command signal from the CNC control to
> the amps, you can see if this is a positioning loop oscillation, or
> just in the servo amp.
>
> The Servo Dynamics does have inductors on the output. They appear
> to be quite small, so it doesn't seem likely they are emitting much
> sound. There is a large transformer (T3) on the circuit board. I have
> only partial schematics of this amp, but I assume this is a DC-DC
> converter that provides isolated power to floating circuits in the
> amp. It may be running at an abnormally low frequency. Without
> diagrams, I can't go much further. You could try wrapping foam
> around this transformer, but if it already runs hot, that might not
> be a good idea.
>
> Jon
>
>
> Addresses:
> FAQ: http://www.ktmarketing.com/faq.html
> FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
> Post Messages: CAD_CAM_EDM_DRO@yahoogroups.com
>
> Subscribe: CAD_CAM_EDM_DRO-subscribe@yahoogroups.com
> Unsubscribe: CAD_CAM_EDM_DRO-unsubscribe@yahoogroups.com
> List owner: CAD_CAM_EDM_DRO-owner@yahoogroups.com, wanliker@...,
timg@...
> Moderator: pentam@... indigo_red@... [Moderators]
> URL to this group: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO
>
> OFF Topic POSTS: General Machining
> If you wish to post on unlimited OT subjects goto:
aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach it if
you have trouble.
> http://www.metalworking.com/news_servers.html
>
> http://groups.yahoo.com/group/jobshophomeshop I consider this to be a
sister site to the CCED group, as many of the same members are there, for OT
subjects, that are not allowed on the CCED list.
>
> NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING THEM.
DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........
> bill
> List Mom
> List Owner
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>