Kossel XL - Migrating from Marlin to reprap firmware

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

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    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


    // 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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