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Testing my new Wanhao i3+. PLA plastic(Wanhao), basic normal quality settings in Cura (I guess 0.1 mm layer, 40 mm/s speed, 60c bed temp, 200c extruder temp). After 1.5 hours of printing quality degraded, it makes some loose structure.

Edit: After finish I noticed that problem exists only in layers where it cycles printing/no printing. There is no problem on layers where it print continuously.

What is the reason can be and how can I fix that?

enter image description here

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  • $\begingroup$ If the problem occurs most when you are doing the most advance/retract cycles, the problem is likely with your advance/retract settings. $\endgroup$
    – Davo
    Jul 13, 2017 at 12:27

3 Answers 3

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This is very likely under extrusion caused by your feeder pressing down too hard onto the filament. If the feeder presses the filament very hard it then gets squished a bit, this is not causing much issues when you're only feeding in one direction as the drive gear is still pulling on fresh filament and shoving the squished part down at a steady rate. BUT once you got retractions things get awful as the squished filament then gets retracted and fed again at the same pace but due to the elongation at a smaller rate of material causing underextrusion.

You can either trade it in to some overextrusion by adjusting the extra length on restart setting, retract a shorter piece of filament (like only retract half a mm or something) or loosen the feeder so it doesn't squish down on the filament as hard.

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  • $\begingroup$ Decreasing the retraction helped me in a simular situation $\endgroup$
    – edosoft
    Jun 11, 2019 at 14:45
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If the problem occurs most when you are doing the most advance/retract cycles, the problem is likely with your advance/retract settings.

Have you tried cutting each of them in half and executing the same gcode?

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It definitely looks like under extrusion.

  1. First thing I would check is the filament feeder to make sure it has a good grip in the filament.
  2. After that I would do another print to see if the problem is repeatable.

If it doesn't repeat, it may have been

  • A temporarily clogged nozzle
  • The filament was undersized in that segment and the filament feeder lost its grip.
  • The extruder got to cold for some reason in that segment and the feeder couldn't push the material through the extruder fast enough.

If it does repeat:

  • Re-inspect the filament feeder
  • Try increasing the the extruder temp to say, 225.
  • Try turning off retraction to see if it is related to those settings.
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