Re: [CAD_CAM_EDM_DRO] Re: servo vs stepper

Hi Keith

Sounds like you have a series II BP. I think the belts give it a little
flex like the couplings do, which helps.I used the original BP motors-I
think they were Sigma. I had CMD drives which worked OK-I think I got about
60 IPM, it's been a few years. I had a chance to try compumotor S-6 or
maybe it was S-8 drives on it one time--wow did they make it scream! I
don't have direct experience with Geckos but from what I've heard they
should be doing much better. Why don't you have the current set to motor
max? Also the software has a great deal to do with it. I use CNCPro now
but back then I was using Dancam. When I switched, it made a big
difference. The other thing I used to test with was just a function
generator, controlling accel by how fast you manually turn the freq up. I
don't know how much configuration your software allows. With some besides
accel and such you can set the step signal width etc and all this stuff is
important. Good luck with it.
Bob

----- Original Message -----
From: "Keith Clark" <mail@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Thursday, September 02, 2004 10:29 AM
Subject: [CAD_CAM_EDM_DRO] Re: servo vs stepper


>
> Thanks Bob, I have a belt drive with a 2:1 reduction to a 5 pitch
> ball screw using a timing belt. This machine was CNC so all the ball
> screws and pulleys were already installed.
>
> What is strange to me is that the geckos are not working even though
> the motors are rated at 7 amps. The motors stall at 5 rev/sec on the
> bench. I know there is very little mechanical load on at least the z
> axis. All three axes stall at about 20 ipm and it is not location
> dependent. The original Bridgeport Sigma motors stalled at exactly
> the same speed. Do you have any suggestions at to what motors you
> have had success with and the oz/in ratings? I am using a Nema 42
> motor that should be able to go 20 rev/sec at 7 amps before stalling.
>
> Thanks
> Keith Clark
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Bob Muse" <mtebob1@s...>
> wrote:
> > Hi Keith
> >
> > I have not been following this thread that closely but having done
> a fair
> > number of retros including series I and series II BP's I would
> encourage
> > you to hang in there a little longer before giving up or scrapping
> what you
> > have and going with servos. I spent a lot of time (being as how I
> had time
> > but no $$) playing with steppers before I got a good handle on them.
> >
> > I think the geckos should work very well. Just a couple of other
> > thoughts/questions that may have already been mentioned but here
> goes-are
> > you using ball screws? How much friction in your ways, are you
> getting good
> > lube flow? I see you mention that your motors are high-inductance,
> > generally that's not that desirable it probably would be better to
> rewire.
> > How is the motor coupled to the leadscrew? My series I used lovejoy
> > couplings with rubber inserts and I think it helped quite a bit.
> Had to
> > change the rubber twice a year or so.
> >
> > The learning curve can be frustrating but having the CNC is worth
> the
> > effort.
> >
> > Bob
> > ----- Original Message -----
> > From: "Keith Clark" <mail@t...>
> > To: <CAD_CAM_EDM_DRO@yahoogroups.com>
> > Sent: Thursday, September 02, 2004 6:47 AM
> > Subject: [CAD_CAM_EDM_DRO] servo vs stepper
> >
> >
> > > As many have read, I have been having a bad time making stepper
> > > motors work using Gecko drives. Several have recommended
> switching
> > > to servos but I have been fearful of tuning the motors etc. Is it
> > > really that difficult and that much more expensive? At this
> point I
> > > have spent $550 on each motor. I am also concerned about the
> > > difficulty of selecting the correct servo motors since I have had
> so
> > > much trouble with the stepper motors. I guess I would appreciate
> > > some encouragement or discouragement at this point especially from
> > > those of you that have done it with a Bridgeport. My machine is a
> > > Boss 6 Bridgeport.
> > >
> > > Thanks
> > > Keith Clark
> > >
> > >
> > >
> > > 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@a...,
> > timg@k...
> > > Moderator: pentam@c... indigo_red@q... davemucha@j...
> > [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
> > >
> > >
> > >
> > >
> > >
>
>
>
> 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
>
>
>
>
>
>
>
>