Can you stop the cooling fan when a print stops?

You cannot stop the fan that blows in the back through the hotend heat sink. It is not intended to be off if the printer is on. The Parts fans are G-Code controlled, but the hotend cooling fan isn't.

M107 will turn the parts fans off.

 

Well you could be right, but that is not how it works in Marlin, so I guess it doesn't matter if you are right or wrong.

 

Technically, you could move the fan to another set of pins and then modify Marlin to tell it where it is and then you might be able to control it. Other printers do stuff like that, but that is not the default behavior.

 

One way might be to locate the two wires that control the hotend fan and trace them back to the Robo Mainboard and disconnect them from the Mainboard and then plug the power plug into the bed power (since it has enough power to drive the fan through a mosfet) near the top of the Mainboard. Those plugs happen to be labeled correctly. The Hotend fan is currently plugged into one of the big green connectors on the Robo Mainboard.

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Then you could download the current Robo flavored Marlin firmware from https://github.com/Robo3D/Marlin/tree/R2, make changes to Marlin to enable BED1. Recompile and export compiled binary then flash through the web interface.

You would have to remember to turn on the fan in g-code before heating the hotend and remember to delay turning it off so you do not clog the heat break. It is not trivial. You will only be able to control the fan via g-code initially but you might be able with modification of /home/pi/.octoprint/config.yaml to also control it via the web interface. Do not expect to ever control it through the LCD unless you can modify Python code on the Raspberry Pi. Please note that whatever changes you make will be undone and need to be redone if and when Robo releases their next Firmware or OctoPrint update (they are currently trailing both Open Source releases by several revisions).

I don't know how you can make this change a trivial matter. and after much thought I believe this is the easiest route to accomplish what you want.

If the Robo Mainboard were not an all-in-one style of controller board (it is still nearly 100% RAMPS 1.4 compatible) there might be a way using a common fan extender used in the two piece Arduino/RAMPS
setups.

 

The amount of energy wasted over an 8-hour time-frame would be ... laughable.
It may not be worth trying to fix this