Marlin to Reprap Speeds



  • Speeds in Marlin for the same hardware are:
    #define DEFAULT_XJERK 7.5
    #define DEFAULT_YJERK 7.5
    #define DEFAULT_ZJERK 0.2
    #define DEFAULT_EJERK 0.10
    #define DEFAULT_ACCELERATION 500
    #define DEFAULT_RETRACT_ACCELERATION 500
    #define DEFAULT_TRAVEL_ACCELERATION 50

    These speeds in marlin were slow but perfect

    My current speeds for duet are:

    M566 X650 Y650 Z12 E120:120 ; Set maximum instantaneous speed changes (mm/min)
    M203 X6000 Y6000 Z100 E1200:1200 ; Set maximum speeds (mm/min)
    M201 X2000 Y2000 Z1250 E500:500 ; Set accelerations (mm/s^2)

    in duet im really just worried about the jerk doesn't seem smooth

    As per the documentation speeds in marlin are in mm/s whilst speeds in duet are mm/min

    So would these new values make sense:
    M566 X1000 Y1000 Z12 E120:120 ; Set maximum instantaneous speed changes (mm/min)
    M203 X30000 Y30000 Z150 E1200:1200 ; Set maximum speeds (mm/min)
    M201 X3000 Y3000 Z1250 E500:500 ; Set accelerations (mm/s^2)*

    I am using standard belts and MGN12H rails

    Please Advise



  • @npm1 IMO, your extruder instantaneous speed change (jerk) is still far too low. Given that any print move will be at the lowest of X, Y or E, then what happens at the end of a move is that the carriage will have to slow down until the extruder speed reaches the "jerk" value before the next move can start. Therefore, it follows that a low "jerk" value for the extruder will have the affect of slowing down the print head because it will "override" the "jerk" values that you set for X and Y. For that reason it is generally best (IMO) to set the extruder "jerk" to a very high value. It will almost never be used unless you use pressure advance and it that case a high extruder jerk value is beneficial. So set to something like 2,000 or even higher (I use 3600) and do likewise for the extruder maximum speed (that will never be used unless it's set too low).

    Other than that, your other new values look reasonable although I'd use a higher extruder acceleration but that depends on what extruder you are using.



  • @deckingman
    Thanks for the response, the extruder im using is a fake bondtech style

    Would you recomend me increase the jerk speeds since when the printer shifts it is very rough...or would that be fine

    I want that kind of move to be a bit more smooth so would i need increase the jerk or decrease it



  • what are you really trying to optimize here?
    printing noise or print quality?



  • @npm1 I'm not sure what you mean by "when the printer shifts it is very rough" and " want that kind of move to be a bit more smooth". What is "rough" and what kind of move? To help you understand, in RepRap Firmware, "jerk" is never applied at the start of a move. Think of it as speed threshold. So towards the end of a move, the print head will decelerate down to the "jerk" speed (the lowest of X, Y or E) before changing direction and starting the next move. "Jerk" is merely a mechanism to prevEnt the print head coming to a complete stop at the end of every move, which is important fir small segmented moves such as arcs.


  • administrators

    @npm1 said in Marlin to Reprap Speeds:

    #define DEFAULT_XJERK 7.5
    #define DEFAULT_YJERK 7.5
    #define DEFAULT_ZJERK 0.2
    #define DEFAULT_EJERK 0.10

    Marlin uses mm/sec for jerk, RRF uses mm/min for all speeds. So multiply the Marlin jerk values by 60 to get the M566 parameters for RRF. That gives:

    M566 X450 Y450 Z12 E6

    That E jerk value is very low and won't play nicely with pressure advance.


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