Smoothie can automatically tune (find) your P, I, and D factors using a process described here.
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 190°C.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:
M500
Which will save the configuration values automatically in a configuration override file.
Learn more about configuration overrides here.
M303 over the web interface, use Telnet, Pronterface, or any other serial terminal.