I wanted a set of Z-braces mostly so that I could align the Z-tower accurately. Turns out this design also makes for a very rigid structure.
These braces were designed to take up as little space as possible, so that they could fit inside my enclosure. I also wanted reverse rods so that I had clean access to the printer bed. These braces use M6 threaded rods, and I covered them with 10mm aluminium extrusions.
An additional benefit is that these braces allow me to lock my enclosure to the printer. Please note that my enclosure differs slightly from the one linked here: https://www.thingiverse.com/thing:2345866 The back compartment of my enclosure is 5mm taller, which gives me room to fit the braces. I have included the updated brackets with the locking lugs if you want to use this enclosure/z-brace combo. Just be aware that the rear enclosure has to sit 5mm higher either through supports, or through modification of the laser cut templates. See my update note. I've now developed brackets that include a 5mm lift if you are already using my enclosure.
I had to move my ribbon cable holder over by around 10mm to fit the brackets. You need: 2 x 410mm M6 threaded rod. 2 x ~380mm 10mmØ aluminium extrusion ( Not required but looks pretty). 2x M5 x 15mm or so bolts (I used M5x25mm). 4x M3 x 10mm bolts. Loctite 8x M6 nuts. Nyloc ones are nice. Heatshrink (Not required, but I used it to stop the aluminium tapping on the threaded rods).
Update: I've added brackets for my enclosure design with a 5mm lift so that you can use this reverse brace with it.
Update: Top bracket has had some manifold errors fixed, so should now work in Simplify3d. Thanks to WaveSupportApparatus. Still planning to update the model to allow for M8 or M10 rods, but not today. :D http://www.thingiverse.com/WaveSupportApparatus
Update 22/9/17 Major update. Meshes cleaned up and simplified. All manifold problems fixed. M8 threaded rod support added. You still need to use the Mk1 if combining with my enclosure, but for everyone else, the Mk2 should be really easy to print. If you use M8 rods, double check clearance between the X-axis motor and the rod at maximum z-height. There should be room, but it will be tight.