The ability to shape the beam of a camera flash is nice and can be used to make interesting effects in your photos (especially if you shoot portraits, or you would like to lighten up a specific object in the frame). In stage lighting a pair of flaps, called barndoors, are often used to shape the beam of a spot light and I decided to make a 3D printed version for use with an external camera flash (this one is tailor-made for Nissin Di622).
I am including the STL files, tailored for my Nissin Di622 flash. They are - Holder.stl, Large_Flap.stl and Small_Flap.stl. You will need to print one copy of the holder and a pair of each flap. I printed mine from PLA, but ABS will work too, even it should be better, since it won't soften if the flash head gets hot. I used 25% honeycomb infill.
Depending on the quality if your prints some post-machining might be needed. Especially with the openings for the bolts and the opening for the flash head (polish it with fine sanding paper to make sure that it won't scratch the rim of your flash head). I used M3 bolts to join the parts.
You will notice that there are four unused openings on top. My reasoning is to be able to attach accessories in future, as filter holder (I make my own "colored gels" by printing on transparencies), or grills.
I am also including the OpenSCAD scad file. If you would like to make a custom design, tailored for a specific flash with a different head you can do it very simple. I scanned the head of my flash on a flatbed scanner. Then I imported the photo into InkScape and traced the outline. I measured the dimensions of the head with a measuring gauge and set the dimensions of the outline to fit the measurements (+ a tolerance of 1 mm). I converted the path into OpenSCAD polygon with the Inkscape to OpenSCAD Converter (http://www.thingiverse.com/thing:25036). If you do this to create your own polygon for the flash head and you can then replace mine with yours - You go to "module FlashHeadShape(h)" in my code and you will see the polygon there. You can just delete it and then paste the code you generated with the converter yourself. If it is oriented horizontally and smaller than 78 x 50.5 mm it should work right away, otherwise you will have to modify the module "Holder". I am sorry, that the code is not commented, I will fix this when I have time.
I used the open source OpenSCAD and InkSCAPE software and then InkScape to OpenSCAD converter (http://www.thingiverse.com/thing:25036). My printer is Velleman K5200 with the Repetier host.
The inspiration came from pure laziness and not wanting to carry too much equipment for lighting when we do cos-play shoots. But I checked online to see if there is already available similar solution and I found that there is at least one company providing similar barn-doors for their own flashes only and some people who "modded" commercial barn-doors for strobes for use with an ordinary flash (http://www.nicephotomag.com/the-latest/the-10-no-mod-barn-door-for-your-flash).