Pulley teeth number

New Home Forum Mostly Printed CNC – MPCNC Advice – MPCNC Pulley teeth number

This topic contains 7 replies, has 5 voices, and was last updated by  Jamie 3 weeks, 4 days ago.

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  • #101207

    What would i need to change in the software side/firmware side of ramps 1.4 to use a 25T pulley on each stepper instead of the asked for 16T.

     

    I want to get this working with what i have on hand

    #101219

    SteevyT
    Participant

    It’s been 3 years since I did this for my 3D printer, but somewhere in Marlin there should be a steps/mm number.  If I recall correctly you only need to know what your current steps/mm are, what distance you commanded, and the distance you moved.

    Then solve (<distance commanded>/<distance moved>)*<current steps/mm> = <new steps/mm>.  You are basically adjusting the steps/mm by the percentage your commanded move was off by.

    I don’t remember exactly where in Marlin the steps/mm variable (or constant? not sure which) though.

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    #101233

    Jamie
    Participant

    If your steppers have 200 steps per revolution
    and if your drivers are microstepping at 32x microsteps
    and if your pulley has 16 teeth
    and if you’re using GT2 belts with 2mm per tooth
    then you should get:

    (32 microsteps / step) * (200 steps / rev) * (1 rev / 16 teeth) * (1 tooth / 2mm) which is 200 steps per mm, which is the default.

    For 25 teeth per revolution you will move a greater distance, 25/16ths as far, and steps/mm will be a lower value by 16/25ths.  If everything else is standard (check your microstepping), you would have 200*16/25 is 128 steps per mm.

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    #101244

    Quarta
    Participant

    the microsteps need to be changed in configuration.h, around line 642

    #define DEFAULT_AXIS_STEPS_PER_UNIT {

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    #101258

    kd2018
    Participant

    … if your drivers are microstepping at 32x microsteps … which is 200 steps per mm, which is the default…

    I believe the default is 16x mircostepping with the config at 100 steps/mm.

    • This reply was modified 3 weeks, 5 days ago by  kd2018.
    1 user thanked author for this post.
    #101410

    so with the 25t pulley ill lose resolution in whatever i am cutting?

    #101413

    I’ve changed it to (128, 128, 512, 128). going to give it a go.

    #101445

    Jamie
    Participant

    The z axis (third number) is probably not scaled by the same amount since I doubt you have a 25 tooth pulley on it.  Just the first two numbers should need changing. (Fourth is for extruder if you ever do that.)

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