Using a process described here http://brettbeauregard.com/blog/2012/01/arduino-pid-autotune-library/, Smoothie can automatically tune ( find ) your P, I and D factors.
Here is an example of the G-code command used to launch PID autotune :
M303 E0 S190
- E0 is the number of the heater or bed temperature control module, determined by the order that they appear in the config file. Here it would be 0 for the hotend, and 1 for the bed.
- S190 is the temperature to autotune for. Use the temperature you will be using your heater at in real life. For a hotend here we use 190c
When you run the command, tuning begins :
Target: 190.0 Start PID tune, command is M303 E0 S190 T: Starting PID Autotune, M304 aborts ok T: 21.3/190.0 @80 1 0/8 T: 22.0/190.0 @80 1 0/8 T: 22.3/190.0 @80 1 0/8 T: 22.1/190.0 @80 1 0/8 Etc ...
It continues for 3 to 8 cycles, heating up, cooling down. Then :
Cycle 4: max: 246.189, min: 227.627, avg separation: 0.418274 Ku: 34.9838, Pu: 39.85 Trying: Kp: 21.0 Ki: 1.053 Kd: 105 PID Autotune Complete! The settings above have been loaded into memory, but not written to your config file.
Now edit your configuration to use those three values ( Kp is p_factor, Ki is i_factor, Kd is d_factor ), reset, and temperature control should work much better. (Also M301 can be used to set the PID values and saved with M500)
Alternatively, you can also enter the following G-code :
Which will save the configuration values automatically in a configuration override file.
Learn more about configuration overrides here : Configuring Smoothie