To much filament at line-start

  • administrators

    Are you quite sure the problem is too much filament at line start, not at line end? That's unusual.

  • @dc42

    Yes I examined this and it is at start - after retraction, so it is by pretraction...?? not a word but you get my meaning..

    Actually I just came to remember i upped the extruder jerk and I read that this might cause this blob. What extruder jerk should I use on Titan extruder and 800mm bowden?

  • administrators

    @pro3d said in To much filament at line-start:

    Actually I just came to remember i upped the extruder jerk and I read that this might cause this blob. What extruder jerk should I use on Titan extruder and 800mm bowden?

    I use a Titan with 600mm Bowden, and I have extruder jerk set to 600. I haven't tried different values.

  • This could be general over extrusion causing a high back pressure, the retract easing the pressure but then the un-retract causing a dump of excess filament at the next start.

    Try seeing how far you need to reduce the extrusion multiplier to get gaps between adjacent extrusion lines then increase the factor until the gaps are a little more than just closed up. Try printing at that settong and see if it eases the issue. It's likely that your retraction settings will need reducing after doing that as they may be larger than needed to compensate for excessive back pressure.

  • @dc42 can I ask acceleration also? My prints are terrible atm

  • administrators

    I have extruder acceleration set to 1000 in M201, and max extruder speed set to 3600 in M203.

  • Is your filament dry? Even PLA can be affected by moisture although it is much less than say petg or nylon. When I have excess oozing i dry out my filament in a dehydrator.

    Also, what type of hotend are you using? I only have 2.6mm of retraction on my ender 3 which now has a bowden fed E3D V6 hotend and I used a printed version of a titan called a Pitan extruder.. Too much retraction can cause its own problems.

  • @jamesm

    I am not sure of the filament but I have printed several types now and they all are terrible even if right out of the box

    Hotend is e3d v6 brand new 1.75 bowden 800mm and retraction I tested from 4 to 7 mm with 6 as the starting point

    Here is config as of now
    M350 Z16 I0 ; Configure microstepping without interpolation
    M350 X16 Y16 E16 I1 ; Configure microstepping with interpolation
    M92 X80.00 Y80.00 Z3200.00 E406.00 ; Set steps per mm
    M566 X900.00 Y900.00 Z60.00 E600.00 ; Set maximum instantaneous speed changes (mm/min)
    M203 X30000.00 Y30000.00 Z300.00 E30000.00 ; Set maximum speeds (mm/min)
    M201 X1500.00 Y1500.00 Z120.00 E3000.00 ; Set accelerations (mm/s^2)
    M906 X1500.00 Y1500.00 Z500.00 E1000.00 I30 ; Set motor currents (mA) and motor idle factor in per cent

    I then added this without any noticable difference:
    M572 D0 S0.25 ; Pressure Advance

    here are some sample prints with PA activated and 5mm retract - PETG 40mms 240/85 add-North

    1_1549306658765_20190201_214616.jpg 0_1549306658765_20190203_134817.jpg

    Here some before PA with 6,5mm with 6.5mm retract - Older PETG - 240/85 50mms
    1_1549306937841_20190204_200051_HDR.jpg 0_1549306937840_20190204_200110_HDR.jpg

  • administrators

    It's hard to compare them because the photos with/without PA are of different parts (i think) taken at different magnification/zoom. The two photos of the red object look as though they would definitely benefit from pressure advance.

  • Have you tried turning off microstepping interpolation on the extruder axis?
    I have had similar issues with to much filament at the start of line, I used negative unretact and PA to compensate for it in the past. Recently I saw some talk in another thread that lead me to try disabling interpolation as a possible solution.
    I have only performed a quick test print last weekend but the results looked very promising, I need to perform followup testing to confirm the results.
    I also changed microstepping on the extruder axis to 32 to help keep the noise from the extruder limited.

  • @mabover oh.. Thanks a lot for this tip. I still fight retraction issues and have almost given up on tuning it... I will try this for sure

  • @mabover
    Do you use coasting in addition to PA?

Log in to reply