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Dual Shaft Nemas

Discussion in 'General Talk' started by GrayUK, Jun 29, 2014.

  1. GrayUK

    GrayUK Master
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    Is it right that you could mount an Encoder to the rear shaft of a Dual Shaft Nema?
    Does that mean you would then have step feedback to the program?
    If so, is it straight forward?
    Or have I got it completely wrong?

    Which wouldn't be unusual.

    Gray
     
  2. Tweakie

    Tweakie OpenBuilds Team
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    Hi Gray,

    I am sure you could do that but I am not sure it would serve a useful purpose for a stepper motor (servo's are an entirely different matter though).

    Stepper motors, assuming a properly constructed machine, do not loose or gain steps - they only move the commanded amount so the driving software always knows the exact position of each motor.

    Tweakie.
     
  3. GrayUK

    GrayUK Master
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    Thanks for that Tweakie.

    OK then. I'll just stick some sound dampers on the ends then.

    Gray
     
  4. Tweakie

    Tweakie OpenBuilds Team
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    Nice one my friend. :)
    Their not 'sound dampers', they are 'mid-band resonance dampeners' - look real cool. :cool:

    Tweakie.
     
  5. GrayUK

    GrayUK Master
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    Well I'll go to the foot of our stairs. :zipit: Silly me. Of course they are. Well, I know what I meant. :p

    Do they actually do anything significant? :confused: I could always stick a flag or something on the Z axis. :ROFL:

    Gray
     
  6. Tweakie

    Tweakie OpenBuilds Team
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    I know you knew - just pulling your leg. :)
    Perhaps best to just stick a flag on it - I think most of the leading stepper driver chips nowadays incorporate pulse-shift to counteract and suppress the resonance when it is detected. I think Gecko were the first to incorporate these chips in their products but others were quick to follow.

    Tweakie.
     
  7. GrayUK

    GrayUK Master
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    Now I didn't know that!!
    Does it work, make it a bit quieter? I didn't realise the answer would lie in the Driver.
    Well well.

    Gray
     
  8. Brian Slee

    Brian Slee Veteran
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    I hate to be contrary with Tweakie but the dual shaft stepper motors are specifically designed to mount an encoder on the back side for closed loop feedback. In some applications like flight control systems the steppers are preferred to the servos because they actively maintain position vs synchros which require a dampening system and braking system.
     
  9. bit53b

    bit53b Well-Known
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    Hey, I stuck a flag on my Z-Axis - turned out well ;)

    motor-flag.JPG
     
  10. Tweakie

    Tweakie OpenBuilds Team
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  11. Tweakie

    Tweakie OpenBuilds Team
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    Good point Brian and I am pleased you made it. :thumbsup:
    I am sure that there are many out there who do use closed loop stepper motor systems with their CNC machines and are extremely pleased with the result but I do wonder if it is really necessary. For me open loop rules. :D

    Tweakie.
     
  12. Brian Slee

    Brian Slee Veteran
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    Hey Tweakie :)
    I agree...for CNC apps I think open loop is preferable in a lot of (if not most) cases. I was thinking more along the lines of other uses for steppers like in aviation or process control systems where they may be used because of their active position holding capability.
     
    #12 Brian Slee, Jun 30, 2014
    Last edited: Jun 30, 2014

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