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Significant temp fluctuations at start of print  

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Significant temp fluctuations at start of print

This started happening recently:

It's not the g-code, so it must be something the printer is doing.  Can anyone give me a clue as to why?

Best Answer by Antonio:

Hi, is the hotend fan clean and spinning regularly?

it can also be due to a damaged\loosen\broken\failed thermistor on the hotend (or its cable)

lastly, maybe fault of the heater cartridge?

 

try to do a PID tuning (calibration menu)

 

Posted : 04/07/2021 3:41 am
Antonio
(@antonio-2)
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RE: Significant temp fluctuations at start of print

Hi, is the hotend fan clean and spinning regularly?

it can also be due to a damaged\loosen\broken\failed thermistor on the hotend (or its cable)

lastly, maybe fault of the heater cartridge?

 

try to do a PID tuning (calibration menu)

 

Parlo italiano...but I'm not an expert....
Posted : 04/07/2021 6:06 am
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 TT
(@tt)
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Topic starter answered:
RE: Significant temp fluctuations at start of print

A PID calibration did not help.

I think something is wrong in the firmware.  The problem only occurs during bed leveling.  It looks like the temperature is increasing during the leveling, but the LCD shows the same temperature.

The gcode shows that the temperature is supposed to reach 210 before leveling starts:

M104 S210 ; set extruder temp
M140 S60 ; set bed temp
M190 S60 ; wait for bed temp
M109 S210 ; wait for extruder temp
G28 W ; home all without mesh bed level
G80 ; mesh bed leveling

However, bed leveling starts before the temperature actually hits 210.  It's as if the M109 S210 command is being ignored. 

As soon as leveling is complete, the LCD instantly shows the new (very high) temperature and then print continues.  Unfortunately, this temperature is way too hot for the filament, which gets burned.

Posted : 19/07/2021 4:27 pm
Antonio
(@antonio-2)
Moderator
a

eventually have you solved the issue or found the source?

You can try a print without using octoprint (disconnect the raspberry cable and print from SD card). Just to exclude something

Parlo italiano...but I'm not an expert....
Posted : 26/07/2021 3:24 pm
TT
 TT
(@tt)
Active Member
Topic starter answered:
Replaced the thermistor

I replaced the thermistor with this one on Amazon, and the problem is now fixed.  Thanks.

https://www.amazon.com/gp/product/B07TYGYWRG/

Posted : 07/08/2021 6:37 pm
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