====== 2023-11-03 - heater PID tuning in 3D printer ======

whenever hotend is changed, or heatbed covered / rebuild, [[wp>PID]] needs to be tuned, to make sure it performs well (i.e.: fast heating, stable temperature, etc.).

the process is simple -- just connect USB cable to your printer and run serial terminal. eg. for anycubic chiron, using ''picpcom'' that'd be:

<code bash>
picocom --imap lfcrlf --echo --baud 250000 /dev/ttyACM0
</code>

first check existing settings with ''M503''. on my firmware it was (stock):

  M301 P20.00 I0.50 D106.55
  M304 P97.10 I1.41 D1675.16

first is heatend, while second is heatbed.

note that stock values differ a lot from values on my customized setup. this is to be expected. make sure to tune these every time you change sth around heating or cooling.


===== hotend PID =====

now run 10x tuning procedure for heatend, for 230 deg.C, and then save it to RAM (i.e. as current values -- that's the ''U1'' part at the end):

  M303 E0 S230 C10 U1

my output was:

  #define  DEFAULT_Kp 25.67
  #define  DEFAULT_Ki 1.80
  #define  DEFAULT_Kd 91.43

now write these values to EEPROM:

  M500


===== heatbed PID =====

next run 10x tuning procedure for heatbed, for 80 deg.C, and then save it to RAM:

  M303 E-1 S80 C10 U1

my output was:

  #define  DEFAULT_bedKp 213.50
  #define  DEFAULT_bedKi 42.59
  #define  DEFAULT_bedKd 267.60

now write these values to EEPROM:

  M500