My four Trinamic stepper motor drivers get hot. I run them at comparatively high current (0.9 A RMS). In order to cool them, I could make and install one of those 'inline' cooling ducts. However, this leaves the 'last' driver in line with warmer air than the first one and the exiting air is not utilized any further. I wanted a cooling duct that generates a parallel cooling flow. As a side benefit, the 'exiting' air is directed over the rest of the board, providing a bit of cooling over the processor & power FETs.
Design and printing
I split the duct into two parts for easier printing. Support is included in the design, only the 'Driver fan duct start' requires some support below the mounting tab. I manually placed it with Simplify3D. I uploaded the g-code file for this part. It didn't print very nice due to stringing and under-extrusion with some single-extrusion thickness walls. The result is quite usable though.
I designed two mounting points (one on each part). The one on the 'Driver fan duct end' broke off. It was still usable with only the single mounting point.
Mounting the fan can be done with M4 screws or simply 4 zip-ties.
Just make sure it kind of sits snug against the drivers.