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PID autotune fails for hotend

Posted by Brummie 
PID autotune fails for hotend
October 05, 2018 11:52PM
Hello,

my heater was too weak to operate at higher temperatures, so I build a heater block for two heaters.
On first test the heater didn't stop at given temperature but jumped over 300°C - so I searched for pid tuning.

In GCode-console I entered: M303 H1 S230
... and this happened:
05:24:33 M303 H1 S230
Auto tuning heater 1 using target temperature 230.0°C and PWM 1.00 - do not leave printer unattended

05:24:39
Auto tune phase 1, heater on
Then an error message popped up saying
Error: Heating fault on heater 1, temperature excursion exceeded 15.0°C

Auto tuning went on with these messages
05:25:05
Auto tune phase 2, heater off

05:25:18
Auto tune phase 3, peak temperature was 292.2

05:27:20
Warning: Auto tune of heater 1 failed due to bad curve fit (A=2048.7, C=131.1, D=5.7)
Is there a way to manage this hotend?
Re: PID autotune fails for hotend
October 06, 2018 02:36AM
You could reduce the H parameter to 0.5 and try again.
Re: PID autotune fails for hotend
October 06, 2018 02:41AM
H word is the heater number.
You probably meant P word.

The point is, I tested for the max P value, that passes autotune successfully - but using those values in print raised the same error.

... but I got it anyway - had to reduce the P value even more.
First test print is already running smiling smiley

cheers
Re: PID autotune fails for hotend
October 07, 2018 03:51AM
The message:

Quote

Warning: Auto tune of heater 1 failed due to bad curve fit (A=2048.7, C=131.1, D=5.7)

is telling you that the heater power is much too high. The values it gives may be correct for your hot end, but the firmware regards a gain (A parameter) above 1500 as indicating that something went wrong.

Edited 1 time(s). Last edit at 10/07/2018 03:51AM by dc42.



Large delta printer [miscsolutions.wordpress.com], Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].
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