Fan duct and Mini Differential IR sensor v1.1 mount for E3Dv6 hot end on Kossel

This is for mounting a 40mm hot and cooling fan and Mini Differential IR height sensor board version 1.1 (see https://miscsolutions.wordpress.com/mini-height-sensor-board/) on a Kossel with E3Dv6 hot end.

Updated 2015-08-17 to raise the sensor board by 0.5mm and add alternative effector mounting hole centres. The STL file suffixed -mk is for the Mini Kossel effector, the one suffixed -rd is for the Robotdigg aluminium effector.

Updated 2016-06-25 to enable Customizer and to provide an o