Re: Lost steps

hi,

I guess one last thing you should try is to exchange motors with
drives. The general thought here is if the problem moves with the
motor then it is the motor that's at fault. If the problem stays with
the drive then it is the drive that is suspect.

Your speed (3rps) is above any possible resonance so that no longer
is a factor.

My best guess at this point is it's the drive. The motor being bad is
a very long shot. Over a 15 year time I have only seen 2 bad step
motors. That is out of thousands I have dealt with.

Mariss

--- In CAD_CAM_EDM_DRO@egroups.com, Ozzie@h... wrote:
> Thanks Mariss,
> The driver is the Camtronics full-step/half-step driver operating
in
> half step mode.
> I dismounted one motor and pulled the pulleys from a second, the
> third
> (Y) is harder to get to. I have plugged both of these two into all
> three axis ports, and one seems to act better than the other which
> makes me suspicious that something is wrong with the motors, but
> again
> one is mounted and the other is loose on the bench. Sometimes I
think
> one axis is acting better than another but the total thing is so
> random that I cannot say for sure.
> The motor temp is F.
> On the bench sitting motor there is some dancing, but not even
enough
> to move it from it's spot. That same motor makes more noise than
the
> other.
> My dummy guess is that these motors are getting false or bad
signals
> somehow, ,,,,but how?
>
> I'm using 5 or 3 inches per minute settings, so with 8000 steps per
> inch that gives 400 or 666 steps per second? I think?
>
> I do not have a scope which is good because I wouldn't know how to
> use
> it and that would be a whole new expense and learning experience,
> that I don't have time or money for.
>
> I have been suspicious of connections from the start, and in fact I
> have corrected many of the erratic anomolies by re-doing the
> connectors. Since the motors are used, a broken wire is a
> possibility,
> but what are the chances on three motors???
> Perhaps I should say that the motors came with the used Shoptask
and
> were used with a power pack kind of control box that controlled one
> axis at a time. The box says "The Motion Group". The motor leads
are
> about 4' long, four wires, shielded but not actually grounded
shield.
>
> What else?
> Well, in about one move in twenty the machine move is dead on!
> Therefore I think the basic settings done by Tim Goldstein are
> correct.
> The moves are never over target, bad ones are always short.
> In perhaps 200 test moves, I have not had a long move.
> Faster moves seem, seem, to have fewer lost steps. I'm not sure.
>
> The no-motion torque of all the motors seems very good. My guess
> would
> be at least the 150 in-oz rating.
>
> Jerry
>
>
>
>
>
>
>
>
>
> --- In CAD_CAM_EDM_DRO@egroups.com, "Mariss Freimanis"
> <geckohall@h...> wrote:
> > By any chance are you using a full-step drive? The symptom you
> > describe is typical if your speed is low (less than 1 RPS)when
> > running a full step drive. The motor will have 2, possibly 3
severe
> > resonance speeds. For a size 23 motor they might be at 20, 40 and
> 80
> > full steps per second.
> >
> > Is there a lot of vibration, like the motor would dance off the
> bench
> > if not held? Does the vibration become noticably less if the
speed
> is
> > changed slightly? Then it is normal full-step drive behavior.
Avoid
> > those speeds.
> >
> > Other possibilites are bad connectors. Gently wiggle or tug on
the
> > wires from both the motor and the PC and see if there is a
repeat.
> > Check the DIRECTION input. A loose connection here could do that
> too.
> >
> > Also check your drive's outputs with a scope if you have one. It
is
> > possible to have a damaged phase output behave that way.
> >
> > The least likely cause is a step motor. Bowling balls are easier
to
> > break than step motors. You can check it by turning the motor
shaft
> > with your fingers. The motor should be disconnected. Compare the
> > torque necessary to turn it to a similar, known-good motor. If it
> is
> > much higher then you may have an inter-winding short. Not likely
> > though.
> >
> > The motor temp sounds normal if you deg F, it is very high if you
> > mean deg C.
> >
> > Mariss
> >
> > --- In CAD_CAM_EDM_DRO@egroups.com, Ozzie@h... wrote:
> > > Update:
> > > After quite a few hours of fiddling without much progress,
except
> > to
> > > improve some wire connections, I decided to romove a motor and
> > watch
> > > it. I was amazed to see it not only stutter once in a while but
> > > sometimes take a backward step.
> > >
> > > Up until now I have wrapped the signal wires inside the cabinet
> > with
> > > aluminum foil and connected the foil to ground, reduced the
> > > acceleration in EMC, reduced the feed speed, and retested the
> > boards
> > > as the Camtronics direction instruct. I also moved the parallel
> > port
> > > cable away from all other wires.
> > >
> > > Is it possible my motors are bad? I don't know their history.
> > > Might I have them wired wrong? They seem to make 99% of their
> steps
> > > right.
> > >
> > > What else might help someone figure it out?
> > > The stutters are not at any particular part of the move. They
vary
> > > fro
> > > one every third revolution to several a revolution. During an
> > hour's
> > > no load testing the motor gets quite warm, maybe 100 degrees.
> > >
> > > Anyone???
> > >
> > > Jerry
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > --- In CAD_CAM_EDM_DRO@egroups.com, Joe Vicars <jvicars@c...>
> wrote:
> > > > True but the cost of precision is comming down.
Precision
> > has
> > > two components, accuracy and repeatability. Machines in general
> > > > are becomming more repeatable (if not more accurate) and
these
> > > machines are used to build other machines thus improving the
> overall
> > > > precision of what is available. The bell curve is getting
> > > narrower.
> > > Six sigma and all that.
> > > > Peace
> > > >
> > > > Terry Ackland wrote:
> > > >
> > > > > ---Ron,
> > > > > I have mill drill in my basement and the lead screw is all
> over
> > > the
> > > > > place. If I need to do anything fussy I have to set up an
> > > indicator
> > > > > because I cannot trust the dials.
> > > > > I can remember many years back working on a new Bridgeport
> with
> > > > > digital readout and expecting it to perform like a jig
borer.
> > The
> > > > > first job sorted that notion out!
> > > > > You have to pay for precision and you cannot really expect
it
> > from
> > > > > what most of us hobbyist are prepared to shell out for.
> > > > > Terry
> > > > >
> > > > > In CAD_CAM_EDM_DRO@egroups.com, Ron Ginger <ginger@s...>
> wrote:
> > > > > > Ozzie@h... wrote:
> > > > > > >
> > > > > > > In repeated attempts to determine the backlash on the
> axis,
> > I
> > > > > find
> > > > > no
> > > > > > > consistency in dial indicater readings. On the X axis I
> lose
> > > > > > > .002-.003" cumalatively in one direction. On the Y axis
> the
> > > > > readings
> > > > > > > are erratic with variations in the.002" area.
> > > > > >
> > > > > > Everyone else seems to be looking for electrical causes,
Id
> > > look
> > > for
> > > > > > plain old mechanical ones. And this is exactly why I do
not
> > > think
> > > > > > software compensation for backlash is worth it. You are
> > finding
> > > its
> > > > > > almost impossible to accurately measure the amount, so
how
> > can
> > > the
> > > > > > software accurately compensate?
> > > > > >
> > > > > > Variations can come from wear in the screws, variation in
> > > friction
> > > > > from
> > > > > > move to move- chips in the way, etc. Try making the moves
> > under
> > > as
> > > > > > constant a load as possible- like while cutting a slot in
> some
> > > > > stock.
> > > > > >
> > > > > > The only solution to backlash is elimination! Ballscrews
or
> > > Moglice.
> > > > > >
> > > > > > ron
> > > > >
> > > > >
> > > > >
> > > > > Welcome to CAD_CAM_EDM_DRO@e...,an unmoderated list for the
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> > > > >
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