Retractions are driving me crazy



  • Hi there!

    I bought a Duet Wifi in January and since then I can not manage to get good retractions when printing. I was playing with all the parameters to try to get better ones with no luck so maybe there is here someone who can help me.
    I have a COREXY machine, with a bowden extruder setup. I have a BMG extruder (not original from triangle labs) and the 25mm bmg original pancake stepper. My hot end is a Mosquito magnum and the bowden tube lenght is 40cm of original Capricorn XS.

    When printing short/small perimeters retractions are perfect but if the path to print is longer I can not get the same result so there it is my problem because I use to print big things like helmets and such.

    I attached here my config as well some pic of the results in printings. I use to print with PLA from Smartfill at 205º.

    I use fw retraction and only wipe in most outer perimeter.

    Also my FW version is 2.03 (2019-06-13b2)

    Thanks for your help!!!

    0_1562998643119_config.g.txt

    This is what I think is a good print

    0_1562998824260_2019-07-10 19.59.11.jpg

    And those are my efforts to try to get same results in bigger prints the printing head goes from left to right every layer:

    0_1562998899098_2019-07-13 07.59.15.jpg



  • @zabana Your description of retraction working on short moves but not on longer ones is a classic example of how pressure builds up in the hot end and Bowden tube. The answer therefore is to use pressure advance to compensate.
    If you are unable or unwilling to do that, then you have to reduce the pressure build up by using a larger nozzle or printing slower.



  • @deckingman thanks for your reply, problem is I tried up to 0.7 P.A. but the blob is still there 😞



  • The gcode would be helpful. You might as well put a vid of how the blob is formed...



  • @zabana What do mean by "and only wipe in most outer perimeter"? What slicer are you using and how do have it configured? Does the slicer override things like acceleration and jerk values that you have set on config.g? If so, please post those settings.



  • @deckingman said in Retractions are driving me crazy:

    "and only wipe in most outer perimete

    Hi!

    I´m using S3D, to wipe is when after a retraction the nozzle travels over a perimeter so it cleans the posible extrussion while is retracting so when it travels is clean and I checked to do it only on the last perimeter just before a retraction due to travel or layer change.



  • I had a problem with blobs like that when I started using nozzles larger than 0.4mm. I ended up solving it by increasing my extruder speed, acceleration and jerk settings. I found that the blob was being laid down while the print head hesitated briefly as the extruder was retracting/unretracting too slowly. I suspect that using larger nozzles exposed the problem for me. Not sure if it will help you, but it is easy to try.



  • I see you have non-linear extrusion configured, have you tried disabling it?

    I also see you're using 64x microstepping and your retraction speed is 5400mm/min. That may be too fast for that level of microstepping which may lead to missed steps, which may mean not retracting as much as you are commanding. This can be compounded by having multiple axis running at higher microstepping. This will also result in much quieter and smoother sounding motors.

    You can run M122 to get a diagnostic report which will show if there have been any hiccups. Regardless, you should probably be using the recommended 16x microstepping with interpolation to 256.



  • Hi!

    Finally I managed to work this out. In igger prints I needed more retraction. Also I needed to increse yet more the extruder jerk to allow better P.A. and retractions. Also in the slicer I discover the command to replace lines in the gcode to use the firmware retraction was not ok so I was using the fw retraction but the slicer unretraction.

    Here you have my final config and my S3D profile just in case it helps to anyone. Also here is a pic of a 40 hours print job.

    Thanks a lot to all of you people!!!

    @deckingman is there any place to see how to do a double gantry like yours?

    0_1563447049962_Config.g.txt
    0_1563436203801_Duet3D Mosquito 0.5.fff.txt

    0_1563437302378_1.jpg
    0_1563437327173_2.jpg
    0_1563437356702_3.JPG
    0_1563436948796_4.JPG
    0_1563437371405_5.jpg
    0_1563437394935_6.jpg
    0_1563436967290_7.jpg
    0_1563436971860_8.jpg
    0_1563437415946_9.JPG



  • @zabana said in Retractions are driving me crazy:

    ...............................
    @deckingman is there any place to see how to do a double gantry like yours?
    .....................................

    In what way? I actually have 3 gantries now. But in any case, you need to build a second CoreXY gantry and install that above your main one.

    If it's to carry the extruders like my second gantry then you map both Alpha motors to X and both Beta motors to Y. Then configure the printer to CoreXYUV mode (M669 K8) which will allow you home each gantry individually whilst keeping them in sync for printing.

    If it's to act as a load balancing gantry like my third gantry, then you don't need to use CoreXYUV mode. Map both sets of motors as above but reverse the motor direction for the upper gantry motors.

    You should find the information on how I did it on my blog, but if you get stuck feel free to start a chat.



  • @deckingman Thanks a lot!
    I´ll dig there to find info. I thought about the system like your second gantry but I don´t know anything about mapping alpha motors in the duet.

    I need to finish first the mod for the printer and after I will try to find in your blog how to map motors.

    I´ll take your word and will ask you if I stuck in the process ☺


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