Re: servo vs stepper

Bob,

Mine is a Series I. I will check out the compumotor drives. Maybe I
will never get to 100 ipm but 20 sure is pittiful. I have set the
Geckos to maximum power and have a healthy power supply. It looks
like from the power speed graphs that the motor just needs more
juice. I am trying to investigate the pulse generator question. I
have not found a software to test. My motion board connects to the
serial port. I am not sure what software to look at. The one I have
is quite expensive meant for professional shops so it ought to work.

Keith

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Bob Muse" <mtebob1@s...>
wrote:

> 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@t...>
> 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:
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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
> >
> >
> >
> >
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