Extrusion not always starting correctly?

  • Hi All,

    I've a few issues in the picture below but I am most concerned about the messy start to the extrusion tracks on a few of the layers. This is a tall skirt printed to reduce curling on some chunky parts. The main concern I'd like to ask about is the poor start to the extrusion on the occasional layer. Weird thing is it isn't always poor.


    Other issues I am aware of is that it does suffer ghosting and issues from the toothed side of the belts running over smooth bearings.

    I think it is something to do with one of the following but welcome other's experience before I dive in on the tweaking!

    ; Filament and Retraction
    M207 S1.8 R0.05 F3600 Z0.0 ; Firmware retraction (s = advance retract, r additional advance.
    M200 D1.75 ; Set extruder 1 to 1.75mm filament
    M572 D0 S0.05 ; Enable pressure advance

    Material: PETG
    Temp: 220C
    Speed: 40 or 60mm/s (not sure which slic3r parameter controls skirt speed. Will look at gcode when I get a chance.)
    Firmware: 1.21
    Hardware: Duet v0.6

  • Didn't see it manifest as severely in today's build but thought the pictured could be a less severe version of it?

    Could it be that when I have really severe resonance or vibration the first bit of extrusion doesn't start well?


    Edit: 0.2mm layers

  • 0_1526989621610__20180522_065444.JPG

    Another resent occurance with PETG. Running duet ethernet now.

  • What size nozzle are you using?

    I have run into this with a 0.8 mmm nozzle on a volcano heater block. The fix is to add add additional unretract volume after retraction. The problem with that is that the effect will vary with the travel distance (time?) between the retraction and the unretraction. Cura has a plugin to make the unretract priming a function of the travel distance, which should fix it.

    I also see gaps in extrusion after travel moves without retraction, such as when the nozzle is printing infill. I haven't figured out what to do about that yet.


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