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How do I tune the Hotend PIDs?  

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UrhoKarila
(@urhokarila)
Active Member
How do I tune the Hotend PIDs?

Hey all,

 

I swapped out/cleaned my heatblock recently and noticed some less-than-ideal behaviour on my last prints - the temperature registered by the thermistor is swingy to an extreme. During the print I'm seeing the temperature stick to a range of +/-10°C -- usually falling from the setpoint (230) down to 220ish, then rocketing up to 240 and repeating the cycle.

 

I know other Prusa printers have easy PID calibration in their wizards but the Mini doesn't. Any idea how to fix this and get back to decent performance?

Posted : 30/09/2020 1:14 pm
karl-herbert
(@karl-herbert)
Illustrious Member
RE: How do I tune the Hotend PIDs?
Posted by: @urhoebeling

Hey all,

 

I swapped out/cleaned my heatblock recently and noticed some less-than-ideal behaviour on my last prints - the temperature registered by the thermistor is swingy to an extreme. During the print I'm seeing the temperature stick to a range of +/-10°C -- usually falling from the setpoint (230) down to 220ish, then rocketing up to 240 and repeating the cycle.

 

I know other Prusa printers have easy PID calibration in their wizards but the Mini doesn't. Any idea how to fix this and get back to decent performance?

I had this problem too. The cause of larger temperature fluctuations was a broken thermistor cable or a short circuit, which naturally changed the internal resistance of the thermistor suddenly and thus falsified the temperature display.
I would check the hardware first before you change the pid values.

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen.

Posted : 30/09/2020 1:40 pm
UrhoKarila
(@urhokarila)
Active Member
Topic starter answered:
RE: How do I tune the Hotend PIDs?

@karl-herbert

Thanks for the insight. The thermistor was giving me a lot of trouble with removal and reinsertion, so it's definitely possible that I damaged it during the process. I'll get some parts ordered for replacing that.

Posted : 30/09/2020 2:15 pm
karl-herbert
(@karl-herbert)
Illustrious Member
RE: How do I tune the Hotend PIDs?

@urhoebeling

The bed pidtuning for the Mini does not work. I have already clarified this with Prusa. But the nozzle pidtuning does. You just do the following:
1.) the most common filament you use for printing, e.g. PETG (Temp 235/85), fan e.g. 50%
2) send the following commands via pronterface or octoprint terminal or gcodefile to printer:
M106 S127 (fan)
M303 E0 S235 C5 (read pid); E0 = extruder nr.; C5 -> the temperatures are controlled 5 times up and down and e.g. the following values are then output:
Recv: #define DEFAULT_Kp 26.45
Recv: #define DEFAULT_Ki 2.22
Recv: #define DEFAULT_Kd 78.81
3.) Enter the received values with :
M301 E0 P26.45 I2.22 D78.81 and
4) Save permanently with M500.
If the Mini allows saving the pid values you have to test. Normally M500 is disabled for most functions. If it is not possible to save it permanently, you can include it in the slicer in the start gcode.

good success 👍 

 

Statt zu klagen, dass wir nicht alles haben, was wir wollen, sollten wir lieber dankbar sein, dass wir nicht alles bekommen, was wir verdienen.

Posted : 30/09/2020 3:43 pm
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