Stringing issues after upgrading from Ramps



  • Ever since upgrading from a Ramps board and Marlin (where I was getting good prints), to Duet Wifi & RRF, I have been having major issues trying to get good prints.
    I was getting major stringing and other issues which all seemed to point to retraction and extrusion settings.
    Finally by accident I came across a post on this forum where another user who had upgraded was having similar issues and some thermistor settings were mentioned.
    I realised then that teh setting I had been given by the online configurator were vastly different to what was being recommended by E3D and other users.
    I have an E3D hotend, but when I did the upgrade I bought generic 24 volts heater cartridges.
    I quick change of settings and a new PID tune and I suddenly had no stringing or major extrusion and could finally start fine tuning.
    So this post is simply a cautionary tale and in the hope that those more knowledgeable can explain where I went wrong so as to save others the same heartache.

    For reference my old settings from the configurator were
    ;M305 P1 T100000 B4138 R4700 ; Set thermistor + ADC parameters for heater 1

    The new settings are
    M305 P1 T100000 B4725 C7.060000e-8

    Thanks in advance



  • Just for some additional info...
    I presume the root of my problem was that the temperature of the hotend was not what I was expecting because of the thermistor values.
    However during my attempts I ran all sorts of temperatures down to the point here I couldn’t reliably extrude at 2mm/s

    And one more question
    I see a variation of about 2-4 degrees from the set value in the active hotend during printing whereas the one on standby and the bed vary by almost nothing.

    This is obviously the effect of fcold filament being added, but what is an acceptable level and how do I improve it?



  • @owend said in Stringing issues after upgrading from Ramps:

    ...................................... And one more question
    I see a variation of about 2-4 degrees from the set value in the active hotend during printing whereas the one on standby and the bed vary by almost nothing.

    This is obviously the effect of fcold filament being added, but what is an acceptable level and how do I improve it?

    First thing. Have you run a tuned the heater temperature control? If not, do it. https://duet3d.dozuki.com/Wiki/Tuning_the_heater_temperature_control

    Edit - ignore the above - I've just re-read your post and see that you've run a PID tune.

    If you have tuned the PID parameters, then do you use a part cooling fan? That's the usual culprit. It's very unlikely that the incoming filament would drop the temperature by 2 to 4 degrees unless you have a very small heater cartridge. Is it a drop in temperature or an oscillation about the set point?

    If it's the part cooling fan, then a silicone sock may help. Or a re-design of the fan duct so that cold air isn't being blown over the nozzle. If it's a temperature oscillation, then increasing the dead time (the D parameter) in your M307 might help.



  • @deckingman
    The 4 deg is oscillation
    Usually 2-3 lower and about 1 overshoot
    Can’t say it’s a problem, just on observation that the standby nozzle remains pretty much flatline.



  • I'd double check your tuning, and make sure the actual tuned parameters are being used. Either by saving them after the tuning with M500 and then adding M501 to config.g to load them, or by copying the results into config.g itself.


  • administrators

    @owend said in Stringing issues after upgrading from Ramps:

    @deckingman
    The 4 deg is oscillation
    Usually 2-3 lower and about 1 overshoot
    Can’t say it’s a problem, just on observation that the standby nozzle remains pretty much flatline.

    If your hot end temperature oscillates when the printer is not moving, identify the M307 H1 command where you saved your tuning results, in config.g or config-override.g. Then increase the D parameter. Try a 30% increase.



  • @dc42
    Oscillation is only on the active nozzle when printing.
    I'll play with D parameter at some point.

    Do I nee an R value in my M305?


  • administrators

    R values ate only needed in M305 in exceptional circumstances.


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