BasW

Hi guys! This morning, I did a somewhat more systematic research to find the cause of my period under extrusion problem. Using Cura 3.6.0, I systematically changed one parameter in the slicing software while keeping the others constant. The results: 1. Disabling jerk control: similar results as using the Slic3r software. 2. Printing on left side of the bed instead of the middle: worse results. 3. Increasing wall line count, to check whether the problem only occurs during the infill or also during wall printing: the problem also occurs during wall printing. Thinking about these results, I slowly changed by ideas about a software fault to a hardware one. Since the problem showed a periodic behavior, I came to the conclusion that the extruder could be the problem, since this one is rotating (and can therefore introduce a periodical error). So I marked a spot on my extruder gear and watched it rotating and, although minimal, I think my extruder gear was rotating more slowly in the under extrusion regions. So, I replaced my extruder gear with a spare one and guess what: problem solved! Apparently: 1. My extruder gear was not perfectly circular, which caused period variation in the pressure on the filament while pushing it through, or 2. Since my extruder gear only has one fixing bolt and the diameter of the hole in the gear may be a little larger than the diameter of the stepper motor axis, the fixing bolt pushes it away from the axis on one side, resulting in a non-concentric fit. This, again, causes a period variation in the pressure on the filament while pushing it through. I did a quick research regarding extruder gears, and I have a question about them: Some of the gears have a kind of ditch on the side in which the filament is supposed to fit, other are competely flat. What is the difference and which one does a better job in your opinion? Thank you all for helping me solving this problem, I really really appreciate it! And, I am sorry for blaming you, Cura...

@BillieRuben good to hear your problem is solved! Is your solution to disable jerk control? Thanks!

Hi @gr5, thanks for your response! Are to refering to the 'clicking' extruder problem? I encountered this problem before, but this time no clicking sound is present. I will look into the extruder rotation tomorrow, I will keep you posted!

Hi! I installed Slic3r and tried the same print and guess what... Different slicer, same problem (sorry Cura for blaming you)! Besides, I tried using a different red filament (although this filament is from the same brand as the black one) using the Slic3r software and again the periodic under extrusion is present (although less visible). Edit: Inspecting the pictures: the under extrusion regions of the black triangle are almost at the opposite location w.r.t. the red triangle. However, both triangles are printed on the exact same spot on the bed.. Honestly, I am running out of solutions.. Has anyone an idea how to solve this? What I tried up to this point: - Downgrading to Cura 3.5.1 - Using Slic3r instead of Cura - Using a different filament - Leveling the bed (a lot of times) - Cleaning my hot end - Trying different hot end temperatures (190-210 C) To give a little bit more background information: I am using a modified Anet A8 printer. I upgraded to a bowden extruder set up, upgraded the firmware to Marlin, use grid bed leveling and 1.75mm PLA with a 0.4mm nozzle. Could it be that there is some fault in the software that is controlling the extruder? Or that my extruder stepper motor is faulty? Thanks!

@smartavionics I tried the 0.5mm line width using Cura 3.5.1. As seen in the picture, the under extrusion periodic profile is exactly the same as before (I was too late to take a picture of the first layer, so the picture is of the third layer). I added the project file and gcode. I will compare the results using another slicer software soon. CFFFP_Plaintriangle.3mf CFFFP_Plaintriangle.gcode

Thanks @smartavionics! What do you mean by project file? Indeed, I used a line width of 0.3mm because in a previous print very tiny gaps in the printed grid where visible, so I changed it from 0.4mm to 0.3mm. I will try to increase this value!

@smartavionics, I downgraded to Cura 3.5.1, and the problem is less present. I attached the Cura 3.5.1 gcode and the .stl file I used, since I overwrote the Cura 3.6.0 gcode. Thanks! Plaintriangle.STL CFFFP_Plaintriangle.gcode

Hi @BillieRuben, I am sort of happy that I am not the only one struggling with this issue. Hopefully an update to the 3.6.0 version of Cura is available soon. I am thinking about using another slicer software too. What are your experiences with Slic3r? Thanks!

I celebrated to early apparently.. Although the prints are getting better, there is still under extrusion at the exact same spot at each triangle (see picture). The file is also attached! Thanks! Plaintriangle.STL

Hi! Thanks for your reply! I downgraded to Cura 3.5.1 and used the exact same settings and the problem is solved. So I guess the malefactor is the 3.6.0 version..

Hi! Has anyone found a solution to this problem? I am experiencing the same issue (see pictures). I am using a modified Anet A8 printer, printing with 1.75mm PLA, slicing with Cura 3.6.0. I leveled the bed several times and increased the hot end temperature, but this did not solve the problem. Since the under extrusion is (almost) perfectly periodic, I am thinking that this is a software fault rather than a hardware one. Thanks!