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Why are my Z Axis Steps per mm so high?

Discussion in 'Controller Boards' started by Geeksmithing, Jan 20, 2018.

  1. Geeksmithing


    Jan 20, 2018
    Likes Received:
    Hi! I recently swapped out an arduino/Gshield for a Spark Concepts xPro.

    After this switch, I have to put in a very high value (1282) for steps per mm on the Z axis for to move the correct distance while calibrating. Is this indicative of a possibly bigger problem?

    The steps per mm for the X and Y axis are only 40 steps per mm. What could be causing this?


    Here are the rest of my grbl settings:

  2. David the swarfer

    David the swarfer OpenBuilds Team
    Staff Member Moderator Builder

    Aug 6, 2013
    Likes Received:
    check the microstepping setting on the Z driver.

    what is the leadscrew pitch? you only need enough microstepps to give you 0.01mm per step.
  3. Giarc

    Giarc Master
    Moderator Builder

    Jan 24, 2015
    Likes Received:
    With an M8 with 1.25 pitch at 1/8 microstepping, 1280 is the steps/mm according to this RepRap Calculator - Prusa Printers But, I do not know if that is the screw you are using. It was just a guess since the math works.

    Are you using belts with a 20 tooth pulley at 1/8 microstepping on X and y?
  4. Chris Scholl


    Jul 22, 2019
    Likes Received:
    Set your value to 400 steps per mm (using x16 microstepping/interpolation) for the T8 lead screws from openbuilds.
  5. David the swarfer

    David the swarfer OpenBuilds Team
    Staff Member Moderator Builder

    Aug 6, 2013
    Likes Received:
    You need to change the microstepping setting on the Z axis driver, it appears to be x8 which is giving this high value which is also EXCEEDING the GRBL max step rate
    Z (micro)steps per mm: 1280.000000 0.00078125mm per step
    Z max steps/s: 42666.666667 Greater than 30kHz!

    reduce to x4 and you can run happily at
    Z (micro)steps per mm: 640.000000 0.0015625mm per step
    Z max steps/s: 21333.333333

    but this may limit your max speed on Z, reducing the microstepping further to x2
    Z (micro)steps per mm: 320.000000 0.003125mm per step
    Z max steps/s: 10666.666667

    will allow a higher max speed while retaining pretty good resolution.

    in other words, on the board you see this

    and you need to move the uSTEP jumper
    jumper settings at Spark-Concepts/xPRO

    turn everything off before changing the jumpers

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