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 temperaturecontrol module, in the order they have been configured. 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 :

M500

Which will save the configuration values automatically in a configuration override file.

Learn more about configuration overrides here : Configuring Smoothie

Network

Do not send M303 over the web interface, use Telnet, Pronterface or any other serial terminal. If sent over the web, the answers will accumulate in Smoothie's RAM and may crash it.