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I've been having tremendously bad print quality lately and have been doing everything I can think of to fix it, none of it is helping. I tried printing a Temp Tower for the first time and since I was paying close attention to the temperature, I noticed that the printer is making some fairly wild temperature swings. My target temp is 200C and it's swinging between 192C and 207C back and forth, back and forth.

That is a video of test printing a cube. Took about 30 mins, video sped up 8x so you can watch the temp changes. It takes about 4 seconds in the video to swing from 192 to 207 so that was about 32 seconds in real time.

temperature tower I printed when I noticed the unwanted temperature fluctuations

  • Monoprice Maker Select Plus
  • 1.75mm PLA (Hatchbox), bought a brand new box
  • Cura 5.2.1

While trying to address the print quality, here are the things I've done before noticing the temperature fluctuations:

  • replaced the nozzle
  • replaced the bowden tube
  • leveled the bed
  • calibrated esteps
  • tried brand new box of filament in case other filament absorbed moisture
  • gently tightened the thermistor screw just so that it was snug, but not overly tight

Here's the thermistor connection on the hotend:

thermistor connection on the hotend

Any suggestions are welcome.

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This looks like a an extruder PID tunning issue.

In Marlin ( I assume this printer use Marlin) there is a auto-tune command for the temperature PID (M303) you can check this page: https://www.3dmakerengineering.com/blogs/3d-printing/pid-tuning-marlin-firmware

You mentioned that you changed the sensor you need to be careful and ensure it is exactly the same type as the stock or to know exactly what type of sensor it is and ensure it is adequately set in the marlin settings a wrong sensor will give you an offset on the measured value but will not generate fluctuations by itself

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  • $\begingroup$ I'm not sure what "PID" tuning is, but I'll read up on and figure it out. I haven't changed any sensors though. $\endgroup$ Commented Aug 25, 2023 at 18:03
  • $\begingroup$ Yup, that was it. I guess that when I replaced the nozzle, the heating characteristics changed and needed to be recalibrated? I read up on how to do the PID tuning, ran it, updated the values, and now the temperature is staying very steady. Thanks! I haven't testing the print quality yet, but this did solve the temp changes problem. $\endgroup$ Commented Aug 28, 2023 at 2:52

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