Layer fan duct and mount for Direct Drive Extruder

This is a layer fan duct and mount kit for Marty Rice's awesome Direct Drive Extruder, when used with an E3D hotend. Together with the E3D 40mm cooler fan duct and mount kit I published earlier (thing #569877), it provides a complete cooling solution for Marty's extruder when used with an E3D-type hotend.

Because of space constraints, a commonly available 5015S 12V blower (centrifugal) fan is used, a mount piece is provided that attaches the fan to the extruder body. The mount piece uses 1 x