Re: Treadmill motors as Servos

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "protman16" <protman16@...> wrote:
>
> John,
>
> After looking at your motors from the link you posted, I noticed
> they are the same ones that I purchased through Surplus Center. From
> my experience these do not work well with Gecko servo drives, at
> least on the set-up I have. The motors seem to have too much torque
> ripple to be used as a servo. I am in the process to find a suitable
> motor to replace them. I might have to change drivers.
>
> Regards,
>
> Protman16
>
>
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "kz1927" <kz1927@> wrote:
> >
> >
> > Thanks Les,
> >
> > I was pretty sure that was you. Thank you for answering.
> >
> > I put some pictures of the motors here...
> > http://www.flickr.com/photos/26361144@N00/
> >
> > I didn't have a D cell put it turns smoothly on a single AA
> > Duracell, I guess thats a good sign.
> >
> > No more lost steps??? I can't believe it!!!
> >
> > Is that the same encoder you used?
> > How does it connect in all of this?
> >
> > Is your mill still running with the treadmills or did you upgrade?
> > I think your old post is from a year or so ago on this topic.
> >
> > I have nearly $1000. tied up in G202's and 600 oz Nema 34's
> > and it's not even as reliable as any of my 3 Hobbycnc boards.
> > It's likely something I'm doing wrong, but I just expected
> > better. When it goes off course on a $20.00 block of plastic, I
> just
> > shut it down and mill by handwheel. And it's done that 75% of the
> > time. I've changed the voltages, changed computers, adjusted the
> > trimpots, use Mach3 and CNCPro ,I need something that works.
> >
> > I got the treadmills for making a spincaster later down the road
> > and was sifting thru old posts for refs on how to control them.
> > That's when I came upon some of your old posts.
> >
> > So someone could have a working servo system where the motors &
> > encoders are a little more than $100.?
> >
> > Naturally I've got to pay for more drives, but if it's reliable
> > enough to leave the room while it's running then it'd be worth it.
> >
> > Which drives do you like?
> >
> > Again, Thanks Les, for helping with this.
> >
> > John
> >
> >
> >
> > --- In CAD_CAM_EDM_DRO@yahoogroups.com, Leslie Newell <lesnewell@>
> > wrote:
> > >
> > > Hi John,
> > >
> > > That was me. The encoder on those motors comes as two parts - a
> slotted
> > > metal disc and a plastic pickup. The disc is pressed onto the
> shaft and
> > > is fairly easy to remove. You must be a bit careful pulling the
> disc
> > off
> > > as I had one fly across the workshop. It took me ages to find
> it.
> > > afterwards. The encoders are only 200 line, giving 800
> pulses/rev.
> > This
> > > is a bit low but it seems to be OK on my mill.
> > >
> > > I used a slightly different motor to the one you show. Mine had
> a
> > > convenient shaft sticking out the back that I ground down to fit
> the
> > > encoder. Also check that the brushes are at right angles to the
> > > commutator. Some are angled and this can cause problems. Surplus
> Center
> > > are very helpful and if you email them, they will have a look at
> the
> > > motor and check the brushes for you. If you already have motors,
> a good
> > > test is to connect them up to a 1.5V D cell. The motor should
> turn
> > > fairly smoothly. If it doesn't turn or if it seems to turn in a
> series
> > > of steps then it won't be brilliant as a servo. If I remember
> correctly
> > > I used 200V rated motors. The higher voltage motors have a higher
> > torque
> > > constant (more torque per amp) and turn slower on 80V. You don't
> really
> > > want a servo spinning at 6000RPM.
> > >
> > > You can't get nearly as much power out of them as you would
> think. The
> > > ratings are for full speed running and fan cooled. They are also
> only
> > > rated for intermittent use. On my Bridgeport I use about a 4:1
> > reduction
> > > ratio between the motors and the screws. This works well, giving
> me a
> > > top speed of about 100IPM with enough torque to snap a short
> 10mm
> > > carbide cutter without even noticing. Normally they run just
> slightly
> > > warm to the touch.
> > >
> > > Apart from the motors and encoders you need Gecko or Rutex
> drives. If
> > > you are already using steppers with Geckos then use Gecko servo
> drives
> > > as they are the same size and hole spacing. I would never go
> back to
> > > steppers. Lost steps? What are they? The only time you lose
> position is
> > > if a drive faults (overload or trying to move too fast) or you
> hit
> > > Emergency stop. Link the drive resets together so if one drive
> faults
> > > they all stop.
> > >
> > > Les
> > >
> > >
> > > kz1927 wrote:
> > > > Thanks Rich!
> > > >
> > > > That's a good starting point. I saw(think I saw) where someone
> > > > used this encoder
> > > >
> > > >
> > http://www.surpluscenter.com/item.asp?UID=2006110919282545&item=10-
> 1834&catname=electric%3E
> > > >
> > > > and this motor
> > > >
> > > >
> > http://www.surpluscenter.com/item.asp?UID=2006110919282545&item=10-
> 1783&catname=electric
> > > >
> > > > but I wasn't clear on how you make it work.
> > > > I think it was Les Newell on a bridgeport, so it MUST work well
> > > > if he says it does.
> > > >
> > > > Is that all one needs (besides some Gecko's)??
> > > >
> > > > Thank you for any help on this.
> > > >
> > > >
> > > > John
> > > >
> > >
> >
>