Kossel XL - Migrating from Marlin to reprap firmware



  • I'm trying to migrate from an old marlin firmware to reprap but I'm having trouble filling in some values since I cant seem to find them in the old marlin configuration.h

    The first one being "maximum carriage travel", now I assume that I can mesure that by pushing one carriage to the minimum possible by going to an extremity of the bed, and it is roughly 440mm but I wonder if this is one of the values that the firmware uses to do precise math or just a safety limit that It wont allow the carriage to go further down. So, is there a formula to calculate a precise value or should I just put my rough mesure with a bit of wiggle room (like the printable radius) ?

    -I can't find max speed (mm/s), if I understood correctly it is the same as the DEFAULT_MAX_FEEDRATE wich is just an old cnc machine term ?

    -From what I've read the current limit of the A4988 drivers is vref*2.5, so I should use 1.25 correct me if I'm wrong.

    -Lastly I would like to know if the huge diffence in the default acceleration ,RRF has 1000, my marlin 3000 and that, oddly my steps per unit are a bit higher (100 vs 80) but my extruder is significantly lower (450 vs 663) , is okay ?

    I'm sorry if these questions have already been answered, I did my best to research them but only found vague answers.

    I attached the Configuration.h (as txt) that I was using in marlin if that can help in any way.
    0_1565152375158_Configuration.txt

    Thanks a lot for helping,
    Wylley



  • @wylley said in Kossel XL - Migrating from Marlin to reprap firmware:

    -I can't find max speed (mm/s), if I understood correctly it is the same as the DEFAULT_MAX_FEEDRATE wich is just an old cnc machine term ?

    https://duet3d.dozuki.com/Wiki/Gcode#Section_M203_Set_maximum_feedrate

    Do note that the RepRapFirmware uses mm/min and not mm/s like marlin, so you need to scale your values accordingly.



  • @wylley said in Kossel XL - Migrating from Marlin to reprap firmware:

    -From what I've read the current limit of the A4988 drivers is vref*2.5, so I should use 1.25 correct me if I'm wrong.

    can you post the specs of your motor. its advised to set the current between 70-80% of the max current of the motor.

    -Lastly I would like to know if the huge diffence in the default acceleration ,RRF has 1000, my marlin 3000 and that, oddly my steps per unit are a bit higher (100 vs 80) but my extruder is significantly lower (450 vs 663) , is okay ?

    Acceleration depends on the print quality you want to have. start with 1000 and increase. if the print quality does not decrease or you do not get lost steps increase it and repeat.

    your steps per mm should not be different. there is something strange going on.
    what pulleys are you using? 20 teeth or 16 teeth?

    its also strange on the extruder. but if the prints are ok.



  • If the marlin board was configured for different microstepping that would account for the difference in steps pr mm.



  • @bearer said in Kossel XL - Migrating from Marlin to reprap firmware:

    If the marlin board was configured for different microstepping that would account for the difference in steps pr mm.

    not from 80 to 100. thats 25%. You cant get that with a different microstepping settings.



  • Too early for quick maths, 12 to 16 is close, but close isn't good enough indeed!


  • administrators

    The Max carriage travel is used only to limit the length of homing moves, so the exact distance is not critical.

    The difference between 80 and 100 steps/mm is 20 vs 16 tooth pulleys.

    The default speed and acceleration limits in the configurator are quite conservative, so increase them if you know your machine can handle higher values.

    HTH David



  • Thank you all for the very helpful and quick replies !
    The last concern I would have is the Beta values for the thermistors,
    for the hotend I just selected the e3d hotend preset since I have an e3d v6 but I have no clue what the coefficient is for the bed thermistor and have no reference for the model, is it ok if I leave it as default (4138) ?



  • where did you buy the bed from?

    if you leave the default your temperature will be off.
    for low pla (60C) the temperature difference can be a few degrees, assuming the common thermistors used. you could work with that.

    higher than that can lead to bigger temperature differences.



  • @veti I just realized that in Marlin, I have both TEMP_SENSORs set to 1 and the comments say that "1 is 100k thermistor - best choice for EPCOS 100k (4.7k pullup)". So I assume that "pullup" is the Beta coefficient and so I will set the bed's one to 4725 too so its the same as the hotend's like in Marlin.

    Makes me think one could do a simple script to migrate from Marlin to RRF.



  • marlin thermistor values are actually in the code

    see
    https://github.com/MarlinFirmware/Marlin/blob/bugfix-2.0.x/Marlin/src/module/thermistor/thermistor_1.h

    // R25 = 100 kOhm, beta25 = 4092 K, 4.7 kOhm pull-up, bed thermistor



  • @Veti
    Oh ok, this is really confusing so both of my thermistors were at 4092 K but the configuration tool sets it to 4725 when I select the e3 hotend preset which happens to be really close to the pullup. So what should I do ? Put both at 4092 like in Marlin or maybe only change the hotend's one to 4725 ?



  • @wylley

    if you have an genuine e3d hotend then yes you need to set B4725 and C7.060000e-8

    most clones v6 hotends do not use a semitec thermistor. for those you do not set it to B4725 and C7.060000e-8



  • @veti It is a genuine one so I had the wrong Beta coefficient for years, good to know, thank you. I'm guessing leaving the bed at 4092 K like it was in marlin should be fine.



  • @wylley said in Kossel XL - Migrating from Marlin to reprap firmware:

    I'm guessing leaving the bed at 4092 K like it was in marlin should be fine.

    yes. If it worked before it should be fine.

    It is a genuine one so I had the wrong Beta coefficient for years

    dont forget about the C coefficient. you need to set it as well as that changes the temperature calculation to the steinhart-hart model. A Beta value in steinhart-hart model has a different meaning.



  • @veti After some research I've found that both of my thermistors had the wrong beta coefficient on Marlin since e3d says to use the TEMP_SENSOR 5 (wich has 4267 K beta value) and that my heatbed thermistor looks like a cheap chinese one with 3950 beta value. So I've put the e3d preset B4725 and C7.060000e-8 for the hotend and B3950 C0 for the heatbed on RRF.

    I guess the manufacturer didnt care about the +-150 difference on both thermistors and just went with TEMP_SENSOR 1 on Marlin.


 

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