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I am getting this under extrusion on my prints but only after travel moves. The rest of the print looks fine.

enter image description here enter image description here

My printer is a Monoprice Maker Select V2 (rebranded Wanhao Duplicator i3 V2) with a DiiiCooler with a radial fan. I was using Repetier 0.92.9 but have upgraded the firmware to Marlin bugfix-2.1.x commit 9e879a5b.

I'm using Cura 5.6.0 and the default Draft profile with the following settings changed:

  • Wall Thickness: 1.2 mm
  • Print Thin Walls: True
  • Infill Density: 10%
  • Infill Pattern: gyroid
  • Print Speed: 50 mm/s
  • Travel Speed: 150 mm/s
  • Initial Layer Print Speed: 20 mm/s

I'm printing with Inland Turquoise PLA at 215 °C and the build plate at 60 °C.

I am printing Kersey Fabrications Speed Test.

I'm pulling my hair out. I've tried the following without making much headway:

  • Completely disabled retraction - made the problem worse
  • Replaced the nozzle with a Micro Swiss Nickel Plated Brass 0.4 mm Nozzle for PTFE lined hotend and replaced the PTFE tube - no improvement
  • Lowered the temperature to 205 °C - no improvement
  • Changed firmware from Repetier 0.92.9 to Marlin bugfix-2.1.x commit 9e879a5b - no improvement
  • Enabled linear advance and tuned it using these instructions. The test pattern looked best at 0.25 but that only made a slight improvement to the issue
  • Set "Max Comb Distance With No Retract" to 10 mm - slight improvement
  • Tried different filament (Inland Black PLA+) - no improvement
  • Disabled "Print Thin Walls" - no improvement
  • Lowered part cooling fan speed to 25% - no improvement
  • Changed the following: - no improvement
    • Printing acceleration 600->1500
    • Retract acceleration 3000->2000
    • Travel acceleration 3000->2000
    • Junction deviation 0.2->0.1
  • Lowered "E maximum acceleration" from 10000->100 - no improvement
  • Checked the extruder gear and it was clean. It has the newer D4 style extruder gear, not the duller slightly hobbed gear that Wanhao originally used.
  • I did the Teaching Tech 3D Retraction Tuning with a base feedrate of 60 mm/s.

For the first print, I did 0.5-3 mm distance, 50 mm/s retract, 20 mm/s advance. There was very slight stringing at 0.5 mm and none in the other sections. All of the sections had slightly jagged edges except for 1 mm.

For the second print, I did 1 mm distance, 20-70 mm/s retract, 20 mm/s advance. There was no stringing and I didn't see any apparent difference between the sections.

For the third print, I did 1 mm distance, 50 mm/s retract, 10-50 mm/s advance. Again, no stringing and no differences between the sections.

None of the three prints showed any signs of under-extrusion.

  • I printed the Teaching Tech 3D Acceleration Tuning Tower and it has the same under extrusion issue in the back left corner inner wall. This would seem to rule out any slicer settings being the cause of this.

    enter image description here

  • I took apart the extruder and found that the v-groove idler wheel that pushes the filament against the extruder gear was full of grease.

    enter image description here

It didn't spin freely, it turned but felt mushy. I cleaned the grease from the wheel and the surrounding area and added a drop of sewing machine oil to each side of the wheel. After that, it spun freely.

I did a cold check of my extruder steps with the extruder removed and found that it matched what I found earlier when I checked it hot through the hotend.

After reassembling the extruder, I reprinted the acceleration tuning tower from the same G-code as before but I saw no improvement to the under extrusion.

  • I took apart the hot end and replaced the PTFE tube again. I was very careful to cut it perfectly straight and exactly the right length so that it was touching each end but not compressed. I also added Kingpin Cooling KPx thermal grease between the heat break tube and the cooling block and between the cooling block and the heatsink. After reassembling everything, I printed the acceleration tuning tower again but saw no improvement.
  • Printed the acceleration tuning tower at 30 mm/s, 0.5 mm retract, and 0.13 linear advance - no improvement
  • Printed the acceleration tuning tower at 225 °C, 195 °C, and 185 °C - no improvement
  • Checked extruder stepper current voltage reference on the Melzi board. I had adjusted the voltage for all four steppers years ago. The extruder stepper is rated for 1.02 A but the voltage reference was set to 0.695 V (0.87 A 85% of rated). It should be set to 90%. Either I set it wrong or it had drifted even though the other three were correct). I tried printing with it set to the factory setting of 0.886 V (1.1 A 109%) and the correct 0.734 V (0.92 A 90%) - no improvement either way
  • As suggested in the comments, printed the acceleration tuning tower with linear advance set to 0.04 and retraction distance set to 0.4 mm - no improvement.
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    $\begingroup$ +1 for the extensive details. A very nice first question. $\endgroup$
    – Greenonline
    Commented Mar 4 at 23:22
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    $\begingroup$ You definitely seem to have ruled out many software-type issues. Is it possible that these underextrusions are physically located close to each other on the bed? If you have a worn or broken wire in your cable chain, it could be losing connectivity during some moves, causing repeated underextrusion in parts of the print volume, if, for example, one of the extruder stepper signal wires is not consistently behaving. It might be worth opening up the cable chains (if they open) and looking for damage. $\endgroup$
    – Tal
    Commented Mar 5 at 15:34
  • $\begingroup$ @Tal I had considered that but the under extrusion happens at different spots on the build plate. Looking at the previewer in Cura and other g-code analysis tools, the spots that are under extruded exactly match locations where the extruder starts extruding after a travel move. $\endgroup$
    – teovall
    Commented Mar 5 at 15:46
  • $\begingroup$ Can you try setting "Max Comb Distance With No Retract" to something like 1.5x to 2x the nozzle width? This essentially stops all unretracted travel except reversals at the end of solid "skin" fill. $\endgroup$ Commented Mar 6 at 1:56
  • $\begingroup$ One detail that seems to be missing is your retraction length. Having retraction too long can cause problems resuming after retract, especially if your filament is at all wet. For a direct drive (I think this machine is DD; correct me if I'm wrong) more than 0.6 mm is probably way too much retraction, but that's assuming you have linear advance calibrated correctly, which you also didn't mention. $\endgroup$ Commented Mar 6 at 2:02

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Printing with a brand new roll of Polymaker PolyLite grey PLA seems to have fixed the problem. I'll have to redo all of my tuning and do some more tests, but there's no sign of the under extrusion so far.

I ran out of the Inland turquoise PLA doing all my testing but I have tried drying the Inland black PLA+. I've dried it a total of 36 hours now at 50 °C and it made no improvement to the under extrusion issue. 24 hours of that was in a Sunlu S1 filament dryer (the original model without a fan) in 6 and 12 hour increments. 12 hours of that was in a convection toaster oven converted to a reflow oven with a Controleo3 kit. I tried drying with and without desiccant packs in both the filament dryer and the reflow oven.

I don't know how or why the filament degraded but it does not seem to be due to any current moisture content.

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