Printbot extruder mount with fan. (Q91492)

An extruder mount replacement for the plain vanilla prointrbit (not LC) which includes a 40mm fan mount. It is a two part device which is box like with a 32mm opening at the bottom for the printer nozzle and airflow. Initial versions had the fan sloping 25 deg so it could be used without the "lid" part but this is difficult to 3D print. I have included the orginal in the SU file but not posted .stl for them ATM. The design is a bit heavier than it needs to be. It is possible heat build up could be problem if the fan is off for extened periods with the hotend hot. The thing doesn't need to be air tight so extra ventilation holes could be added. The fan worked too well and I had to partly cover the intake to tame it down. Some tuning it likely for changes in room temperature, filament, layer height and the size of the print.