In a discussion on the Marlin dev page I've just been told that it's possible to change the temperatures of the pre-heat ABS and PLA presets in Marlin as follows: Currently we have M145 to change the presets for hotend temp, bed temp, and fan speed. For example: M145 S0 H185 B60 F100 M145 S1 H240 B100 F0 These can be saved to EEPROM also. There's no option to set the material's name, but that could be added. Allow up to 10 characters, or something. I guess "S1" is "Substance 1" or something? Now turning the Parts Fan on in the preheat stage, is that an interesting thing to do? It will enable the system to achieve thermal stability.... But when is it a good idea to print the first layer with the fan high?