Re: [CAD_CAM_EDM_DRO] Closed Loop PC Based CNC

If you stepper solution works well apart from the lost steps then I
would have thought your best option would be to get servo drives that
can accept step/direction. That way you retain your front end but have
the advantage of servo control.

More and more drives these days accept step/direction. For a cheap
solution using brushed motors try <http://www.geckodrives.com/> or
<http://www.rutex.com/us/>

Les

nitewatchman5 wrote:

>
>
> I have a Bench Mill currently running with stepper motors in an open
> loop configuration. We are running production parts in fixtures and
> after running several parts to several dozen parts, sizes and
> locations start to drift due to missed steps. Slowing traverse rates
> down and extending longer acc/dec ramps helps but the problem is still
> there depending upon cutting forces and the shear number of axis
> reversal moves. Additionally, slowing the machine to fit the
> speed/torque curve of the stepper motors increases the part cycle time
> and the part cost directly.
>
> As a solution I want to take this machine to a true closed-loop system
> using AC Servo Motors. While I have retro-fitted several large
> machines (25'+ travel) with Fagor and AB 9-Series controls,
> maintaining a PC based control presents some problems.
>
> A likely scenario would be to use a matched servo drive and motor
> combination such as the Yaskawa DR-1/SGM set for each axis. The
> encoder feedback from the motor for commutation can be redirected to a
> Controller board in the PC for position error control. The controller
> would output a +/-10VDC analog signal to the Servo Amps to control
> speed and direction. The calculated following error can then be
> intergrated into a PID Loop to control speed, torque and location.
>
> There are several interesting controllers on the market such as the
> Galil, Delta Tau and Servo to Go. The Galil especially looks very
> powerful and is sometimes found on eBay for a reasonable price. The
> big question however is the Front-End software to drive the
> controller, does for example EMC support these controllers?
>
> Advice would be appreciated, practical experience perferred -
> theoretical suggestion catalogued. If we can find no other solution we
> will refit the machine with a Fagor 8025M control.
>
> nitewatchman
>
>
>
>
>
>
>
>
> 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@... davemucha@... [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
>
>
> Yahoo! Groups Links
>
>
>
>
>
>
>
>
>