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  1. #1
    Jailcee's Avatar
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    Using Cura along with the updated Marlin firmware

    Since updating my firmware to use Tim's EZABL I noticed a change in the quality of my prints. I played with my jerk and acceleration settings but they seemed to do nothing. That's when I started to dig a bit.

    Using Cura 2.5 and 2.6, my printer is set up as a custom printer using GCode flavor "RepRap (Marlin/Sprinter)".

    In Cura I have these as my settings:
    Print Accel: 800
    Travel Accel: 850
    Print Jerk: 10
    Travel Jerk: 15

    According to documentation (http://marlinfw.org/docs/gcode/M204.html and http://marlinfw.org/docs/gcode/M205.html) this should produce the following Gcode:
    M204 P800 T850
    M205 X10 Y10


    What I find in the GCode instead is:
    M204 S850
    M205 X15
    M204 S800
    M205 X10


    Clearly that isn't going to work. I don't think there is a way in Marlin to set different travel and print jerk values but it is possible to set it for X and Y. I've no ideal how the M204 command is being interpreted but I suspect it isn't which means the printer is using the firmware defaults set in configuration.h which are:

    #define DEFAULT_ACCELERATION 1000 // X, Y, Z and E acceleration for printing moves
    #define DEFAULT_XJERK 20.0
    #define DEFAULT_YJERK 20.0
    #define DEFAULT_ZJERK 2.7
    #define DEFAULT_EJERK 5.0


    I now understand why I was getting frustrated trying to reduce ghosting on my CR-10 using Cura. Looks like I may need to set acceleration and jerk in my start GCode. I'll run some tests now that I've clued into this.

  2. #2

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    silly question, if you set it in start gcode for the printer setting will the cura parameters then overwite it with the dodgy values?

  3. #3
    Jailcee's Avatar
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    Quote Originally Posted by Ralgon View Post
    silly question, if you set it in start gcode for the printer setting will the cura parameters then overwite it with the dodgy values?
    Yes. Cura adds its code AFTER your start code.

    I got confirmation from one of the Cura coders:

    "Yes, in the more recent marlin source they expect the X and Y jerk to be specified separately as you show above but what cura does is compatible with earlier marlin versions. Looking at the earlier marlin code, it would ignore a Y value if it was specified so I don't see why we can't change cura to output both X and Y values."

    So it looks like if you want to set your accel and jerk settings using the new firmware you need to do it by changing the max accel and jerk settings in the firmware eeprom which will override whatever the Gcode says.

  4. #4
    Jailcee's Avatar
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    After further research I have found several differences between Marlin 1.1 and the version that comes with the CR-10.

    - Hot end temperature calibration is way off, by up to 15c. See the other post in on calibrating hot end temperatures for more details.
    - Jerk settings are not handled properly in Cura. Since that wasn't caught by the Cura team I suspect other changes were not caught as well.
    - One such change seems to be how the firmware resumes printing after a move. I've found it necessary to prime the nozzle with .4mm^3 after a retraction.

    I'm still working through the print quality issues and I'll update more as I find them.

  5. #5
    Jailcee's Avatar
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    Good news, the Jerk settings issue has been fixed in the Cura code and will be part of version 2.7.

  6. #6

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    Quote Originally Posted by Jailcee View Post
    Good news, the Jerk settings issue has been fixed in the Cura code and will be part of version 2.7.
    Wow that's great. thanks for looking into that.

    Wild.

  7. #7

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    But won't the firmware continue to ignore them?

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