CAD CAM EDM DRO - Yahoo Group Archive

Re: gearmotors,encoders

Posted by jmw@c...
on 2000-11-09 22:58:29 UTC
Thanks, Mariss. I understand what you're saying about no-windup
connections between the motor and screw, and I suppose that also
includes gearmotors.

What do you think about part 2), putting the encoder on the non-motor
end of the screw? Is there likely to be a problem due to, ah what
would an ME call it--the torsional flexure of the lead screw? I'm
guessing it's going to be a lot easier to find surplus servos with
tachs than with 1000 line encoders.

Incidently at least one encoder mfr (Dynapar) suggests the fiendishly
expensive helical connectors for connecting encoders.

--Jack





--- In CAD_CAM_EDM_DRO@egroups.com, "Mariss Freimanis"
<geckohall@h...> wrote:
> Hi,
>
> The problem is backlash. The servomotor will thrash back and forth
> over a distance equal to the backlash, building up a good head of
> steam on each transit. Expect considerable vibration as it does so.
>
> The motor gets its guidance from the encoder. In the backlash
region,
> the motor can move, (and it will) without any compensating motion
of
> the encoder. The motor then is uncontrolled and will accelerate. If
> the backlash is large, the motor speed will be cosiderable when the
> encoder finally moves. It will then reverse direction and the
process
> will repeat.
>
> Mariss
>
> --- In CAD_CAM_EDM_DRO@egroups.com, jmw@c... wrote:
> >
> > ------------------------------------------------------------------
--
> -
> >
> > Apologies in advance for burning bandwidth; I've asked about this
> > before--but I still don't get it. Why not put rotary encoder(s)
on
> > the non-motor end of the screw rather than on the motor shaft? It
> > seems like one wants to know the position, direction and speed of
> the
> > screw rather than of the motor per se. So if it's no worse,
> possibly
> > even better, to have the encoder on the far end--then what would
be
> > wrong with a slightly flexible coupling (e.g. Lovejoy) between
the
> > motor and the screw? I can see that during accel and decel the
> motor
> > and screw could get out of phase, and maybe in some bitter state
of
> > the world this could feed on itself, but couldn't this problem be
> > tweaked away with a little gain correction? I like slightly
> flexible
> > connections; they absorb vibration, correct for slight
> misalignment,
> > would put some allowance for a few thou of axial heat-growth of
the
> > screw in the system, etc.
> >
> > Thanks.
> >
> > --Jack

Discussion Thread

jmw@c... 2000-11-09 21:32:39 UTC gearmotors,encoders Mariss Freimanis 2000-11-09 22:41:42 UTC Re: gearmotors,encoders jmw@c... 2000-11-09 22:58:29 UTC Re: gearmotors,encoders Alan Marconett KM6VV 2000-11-10 10:51:07 UTC Re: [CAD_CAM_EDM_DRO] gearmotors,encoders Mariss Freimanis 2000-11-10 10:58:56 UTC Re: gearmotors,encoders Jon Elson 2000-11-10 12:11:59 UTC Re: [CAD_CAM_EDM_DRO] Re: gearmotors,encoders jmw@c... 2000-11-10 12:17:16 UTC Re: gearmotors,encoders jmw@c... 2000-11-10 12:22:47 UTC Re: gearmotors,encoders Mariss Freimanis 2000-11-10 13:32:24 UTC Re: gearmotors,encoders dave engvall 2000-11-10 13:34:50 UTC Re: [CAD_CAM_EDM_DRO] Re: gearmotors,encoders Mariss Freimanis 2000-11-10 13:45:44 UTC Re: gearmotors,encoders jmw@c... 2000-11-10 13:50:29 UTC Re: gearmotors,encoders dave engvall 2000-11-10 13:58:14 UTC Re: [CAD_CAM_EDM_DRO] Re: gearmotors,encoders Mariss Freimanis 2000-11-10 14:06:55 UTC Re: gearmotors,encoders Mariss Freimanis 2000-11-10 14:09:54 UTC Re: gearmotors,encoders dave engvall 2000-11-10 14:14:46 UTC Re: [CAD_CAM_EDM_DRO] Re: gearmotors,encoders dave engvall 2000-11-10 14:19:40 UTC Re: [CAD_CAM_EDM_DRO] Re: gearmotors,encoders Jon Elson 2000-11-10 14:46:44 UTC Re: [CAD_CAM_EDM_DRO] Re: gearmotors,encoders Mariss Freimanis 2000-11-10 15:05:20 UTC Re: gearmotors,encoders Jon Elson 2000-11-10 15:11:30 UTC Re: [CAD_CAM_EDM_DRO] Re: gearmotors,encoders dave engvall 2000-11-10 16:09:05 UTC Re: [CAD_CAM_EDM_DRO] Re: gearmotors,encoders Mariss Freimanis 2000-11-10 16:19:32 UTC Re: gearmotors,encoders Tim Goldstein 2000-11-10 17:23:33 UTC RE: [CAD_CAM_EDM_DRO] Re: gearmotors,encoders jmw@c... 2000-11-10 18:29:53 UTC Re: gearmotors,encoders Jon Elson 2000-11-10 21:58:50 UTC Re: [CAD_CAM_EDM_DRO] gearmotors,encoders jmw@c... 2000-11-10 22:25:22 UTC Re: gearmotors,encoders Jon Elson 2000-11-10 23:18:24 UTC Re: [CAD_CAM_EDM_DRO] Re: gearmotors,encoders ballendo@y... 2000-11-11 04:35:06 UTC re:Re: gearmotors,encoders ballendo@y... 2000-11-11 04:49:46 UTC Re: gearmotors,encoders Wally K 2000-11-11 05:26:54 UTC Re: gearmotors,encoders Smoke 2000-11-11 09:15:27 UTC Re: [CAD_CAM_EDM_DRO] Re: gearmotors,encoders wanliker@a... 2000-11-11 11:58:33 UTC Re: [CAD_CAM_EDM_DRO] Re: gearmotors,encoders Jim Register 2000-11-11 12:03:01 UTC Re: [CAD_CAM_EDM_DRO] Re: gearmotors,encoders Jerry Kimberlin 2000-11-11 14:26:25 UTC Re: [CAD_CAM_EDM_DRO] Re: gearmotors,encoders Jim Register 2000-11-12 10:10:13 UTC Re: [CAD_CAM_EDM_DRO] Re: gearmotors,encoders Brad Heuver 2000-11-12 18:59:12 UTC Re: gearmotors,encoders Jon Elson 2000-11-12 22:23:52 UTC Re: [CAD_CAM_EDM_DRO] Re: gearmotors,encoders