How does the home position work on a Prusa i3 RepRap Printer?

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    By what process does the Prusa i3 determine it's home position?



    I have a feeling that it works like this, but I'm not entirely sure about it:




    1. If none of the end stops are activated; assume you are somewhere between Max-X, Max-Y, Max-Z and the point 0,0,0.

    2. do


      1. For axis in Axies


        1. If axis endstop not signaling


          1. subtract 100 steps from axis.




    3. while endstops are not signaling, or if point 0,0,0 not reached;


    The answer to this question is completely dependent on the firmware your printer is running and the configuration of said firmware (the homing order in Marlin is configurable, you have a variety of options such as "home Z first" or "home X and Y simultaneously").

  • Flautarian

    Flautarian Correct answer

    6 years ago

    It works like you describe, but it does not move all axes at the same time. It first moves the X-axis, subtracting steps while the X endstop is not pressed. When the X-axis is is homed (the X-endstop is gets pressed) it repeats the procedure for the Y-axis and finally the Z-axis.


    I've always found it odd that 3D printers have basically the reverse homing sequence from conventional cnc machines. Most industrial mills, lasers, and routers homing order is Z, Y, then X. This is to reduce the chances of crashing into any fixtures mounted on the work table.

    3d printers generally have the z endstop at the bottom rather than the top for better or worse. So homing z would make it crash into anything under it. Many people (me included) put the z endstop on top because that just makes more sense.

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