First steps and some questions...



  • Hello all!

    I am currently planning and building a 300x300x300 CoreXY Printer (derived from Railcore II prinziple).
    First thing whilst doing planning was to build up the upper part of the frame to figure out the XY-Kinematics.
    To keep spirits up i would realy like to move X-/Y-axis around as a test. Following are some questions prior to my tests as i want to make sure to not make expensive errors. 😉

    I want to do a minimalistic setup to basically just put in steppers for X and Y axis. Furthermore i could put in 3 steppers for the Z-Axis (those would be not connected to the mechanics so far). No endstops, no extruder, no heaters, no temperature sensors.
    I tried to build that up in the Reprap-Firmware configurator and it came out like this:

    0_1559554178871_config.g 8_1559554190329_stop.g 7_1559554190329_sleep.g 6_1559554190329_resume.g 5_1559554190329_pause.g 4_1559554190329_homez.g 3_1559554190329_homey.g 2_1559554190329_homex.g 1_1559554190329_homeall.g 0_1559554190329_bed.g

    Could anybody please have a look it those files are plausible and good to go for my minimalistic approach?

    The steppers i am speaking of are as following:
    ACT 17HM5424 Hybrid
    NEMA 17
    0,9 ° per Step,
    0,8 A per Phase
    2,4 Volt
    0,8 Ohm per Phase
    https://cdn-reichelt.de/documents/datenblatt/X200/17HM5424DATASHEET.pdf

    So my next question is: Do i put 800 mA or 1600 mA in for the Motor Current (M906)?
    In my config above i put in 1600 mA as it s two phases (2 * 800 mA). Is that correct?

    Thank you very much in advance.

    Have fun
    Mathias



  • you aim for between 50-80% of the max current of the motor.

    so start with 600mA.

    then see
    https://duet3d.dozuki.com/Wiki/Choosing_and_connecting_stepper_motors
    Checking connected stepper motors



  • @licantrop Take not of what @Veti said about your motor currents.

    Obviously without any end stop switches connected, do not attempt to run any of the homing files. For basic movement checks, you need to either put M564 H0 in your config.g file (but take it out later unless you really know what you are doing) or use an S2 parameter in any G1 moves. For a novice (and no disrespect intended) , the S2 parameter is safer option.



  • Hello again!

    Thank you for your replies.

    In the meantime i could find the appropriate entry at the G-Code reference and it confirms Veti's reply. It s clear to me now after reading definition for M906:
    Sets the currents to send to the stepper motors for each axis. The values are the peak current per phase in milliamps.
    My fault for not looking it up beforehand.

    @ Ian: Yes, i ll be carefull and will put in M564 H0. I did not think of that until now. Thank you.

    But is there anything else which can go wrong if i follow "first steps" documentation and using config similar as above?
    I just do not want to destroy anything uncautiously....

    Kind regards
    Mathias



  • @licantrop Just play close attention to the wiring - double check everything before you turn on. You could try even lower motor currents just to test. Then if something goes badly wrong, a motor will stall before any physical damage ensues. If you set the current too low, you'll get missed steps or the motor might not turn at all but you won't damage anything.

    Once you know that you have basic movement, you next step should be to fit the end stops and/or Z probe. Make sure the end stops work first, then do the homing. Once you can home all the axes to their minima, then jog them all to their maxima and note those distances. Put those values in config.g (M208 S0). The configuration tool can only work on the values you've put in and the true maxima may be less than the 300x300x300 you've set. Once you can home the machine from then on, any moves you attempt will respect the axes limits and won't go beyond them. So you can remove the M564 H0 if you used it.


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