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Thermistor temperature fluctuations  

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Sid
 Sid
(@sid)
Active Member
Thermistor temperature fluctuations

Hi All 😊 

My Prusa Mini's have been running for hundreds of hours, but now i'm getting issues on all of them. Fan's get broken, thermistors stops working and after a replacement under warranty (thumbs up prusa support 👍 ) it's all working again so that's great. But now the strange thing i've noticed that print profiles i've been using several years now, are not consistent anymore. And I didn't understand it, it took me a really lot of time, but now I think i'm getting close, at least for a part of it.

On the printers where i've changed the thermistor I got a lot of stringing en blobs. And after a lot of cleaning and changing PFTE tubes, etc etc. I found out that it was as simple as turning down time hotend temperature by 10 degrees. To be sure it was the new thermistor i've moved it to a printer without this issue and indeed after replacement it also suffered the same issue. Reconnecting the old thermistor solved the problem.

Now I know this i can tune the temperature on the specific printers, but is there a way to setup the printer that it always retracts 10 degrees of the GCODE temperature?

 

Posted : 04/12/2022 7:10 am
Az3Dip liked
Robert
(@robert)
Eminent Member
RE: Thermistor temperature fluctuations

The temperature shown on display is not the same as the real temperature. I therefore always need to add +5deg to the nozzle  and bed values. Is there an option to "fine tune" the temperature in mimi+ firmware ?

Posted : 09/12/2022 10:35 am
Sid
 Sid
(@sid)
Active Member
Topic starter answered:
RE: Thermistor temperature fluctuations

No unfurtunatly not, at the moment I enter them in Octoprint as an temperature offset but this has to be re-entered every time it powered off.  It works but it would be better to program it somewhere in the EEPROM so it doesn't depends on external software.

Posted : 10/12/2022 5:55 am
Zoltan
(@zoltan)
Moderator
RE: Thermistor temperature fluctuations

Sid, did you do a replacement by original prusa mini thermistor?

even an old man can learn new things 🙂
Standard I3 mk3s, MMU2S, no closed box, Fusion 360, PrusaSlicer, Windows 10
PRUSA MINI+ Prusalink + Prusa Connect

Posted : 11/12/2022 6:18 am
Zoltan
(@zoltan)
Moderator
RE: Thermistor temperature fluctuations

One possible work around can be to create a copy of the filament profile in prusaslicer and change the temperaturs

even an old man can learn new things 🙂
Standard I3 mk3s, MMU2S, no closed box, Fusion 360, PrusaSlicer, Windows 10
PRUSA MINI+ Prusalink + Prusa Connect

Posted : 11/12/2022 6:20 am
Sid
 Sid
(@sid)
Active Member
Topic starter answered:
RE: Thermistor temperature fluctuations

Yes it are original prusa replacements. Yesterday i've measured multiple thermistors, two new ones and 2  older ones

Unsued new 1 -> 131 kΩ 
Unsued new 2 -> 126 kΩ 
Old 1 -> 130 kΩ 
Old 2 -> 138 kΩ 

All measured next to eachother at room temperature. I don't know if this 'small' differences could be a cause of the different temperatures. Maybe they also have a different curve when heating up or cooling down.

It would be great to get more tuning at printer level. If you use one printer editing the gcode isn't a big problem, but when using multiple printers it's difficult to keep track of and a lot of work. (I sync all gcode accross my printers)

 

Posted : 11/12/2022 7:24 am
Robert
(@robert)
Eminent Member
RE:

I am using originál prusa with no mods. Even ať the moment there are different temperature shifts on bed and head, looks the only real solution could be a fw temp_shift parameter(s). I'll try to write the suggestion/request into github. Thanks you. 

This post was modified 2 months ago by Robert
Posted : 11/12/2022 11:10 am
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