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I changed the filament, and to adjust filament temperature, I printed a test model and it looked good:

enter image description here

But printing another part did not go so well:

enter image description here

enter image description here

After the failed print I ran another test: enter image description here

Еverything is done with the same settings. And I think the temperature and settings are okay.

Is it possible to have a missed step on the Z axis, and this has caused the crushing of the layers or bad filament quality.

Where does the problem come from?

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    $\begingroup$ It looks like over-extrusion. Please tell us the machine, slicer, temps, speed, layer thickness, and material used. $\endgroup$
    – Davo
    Apr 14 '19 at 21:00
  • $\begingroup$ Missing Z steps results in shorter or skew prints, is the cylindrical part with bubbles shorter than it should be? Is the extruder stepper stuttering? Please also add some settings as asked by @Davo. Thanks! $\endgroup$
    – 0scar
    Apr 16 '19 at 10:58
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It definitely looks like the temperature is too high

but it can also mean that

  • the speed is too low and/or
  • the cooling fan is not driven correctly and/or
  • over extrusion could play a role here

this is the scenario with all these issues together

too high temperature melts too much filament which is put by too slow movements

;)

check the printing when your object changes from well printed to this ugly state

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Looking at the second photograph and the way that the filament switches abruptly from smooth to irregular deposition, I would say that you have a partially clogged nozzle.

Pre-heat the nozzle and extrude some filament. It should drop straight down from the nozzle. If the filament curls as it comes out of the nozzle, the nozzle is partially clogged. You may be able to clear the clog by doing what is called a "cold pull":

Pre-heat the nozzle so that it is possible to extrude filament. Then switch off the heater and allow the temperature to fall below the pre-heat temperature of the filament (140°C for PLA, say). Now disengage the extruder gears and gently withdraw the filament completely from the hot end. On removing the filament completely from the printer, you should find a "bullet" on the end of the filament in the shape of the melt chamber. Hopefully, the dirt that caused the clog will be embedded in the bullet.

In order to prevent dirt from entering the nozzle, it is a good idea to install a filament cleaner. This can be as simple as a piece of sponge containing a couple of drops of light machine oil, or you can make something a little more sophisticated. There are plenty of designs that you can download on Thingiverse.

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    $\begingroup$ The glass transition temperature of PLA (Tg) is about 60 ℃, not 140 ℃. Please remove the reference to Tg. $\endgroup$
    – 0scar
    Apr 15 '19 at 4:22
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    $\begingroup$ @0scar Oops! Thanks for that. $\endgroup$
    – Mick
    Apr 15 '19 at 4:31
  • $\begingroup$ @Mick Thanks for answer, but i have filament cleaner and i think the nozzle is not clogged. $\endgroup$ Apr 17 '19 at 11:00
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From third picture - moisture!

Is new filament cheap? I guess it was too long on stash and/or bad package.

Look for Maker's Muse's video on Youtube about this topic.

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    $\begingroup$ Moisture has an effect on printing filaments, but not like shown in the image you are referring to. $\endgroup$
    – 0scar
    Apr 15 '19 at 21:11

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