Rotary encoder accuracy for Z axis.



  • In a previous, now locked thread on rotary encoders https://forum.duet3d.com/topic/1599/rotary-encoder it's pointed out that the encoders would need to be very accurate in order to replace stepper motors operating at the precision required for 3D printing.

    Clearly, this would vary, relative to the amount of steps per mm, and the desired accuracy of a system. Many 3D printers have much higher steps per mm on the Z axis, compared to X & Y. Someone correct me if I'm wrong, but higher steps per mm would mean a lower requirement for accuracy in a rotary encoder.

    Based on some rough calculations, my Z axis would need a rotary encoder accurate to 1/80th of a turn, to print 50 micron layers.

    This appears to be something that should be possible to produce in a DIY fashion, potentially utilising DC motors recovered from E-waste. But it would take a bit of work to get it up an running, so I don't want to go into this on incorrect assumptions.



  • With enough gearing to get to high steps per mm, an encoder can be have sufficient resolution when measured at the moving axis after the gears. (And a Z axis with a leadscrew is effectively gearing).

    At the same time, the encoder is still giving up resolution as compared to a .9 deg stepper operating in microstep mode.

    Therefore, the question must be asked, why?



  • Primarily to make use of E-waste motors.


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