This is a printed-bearing stabilization upgrade for the brackets at the top of the Z-axis rods on the HICTOP Prusa i3, extruded aluminum version, and similar printers. The design is fully parameterized with OpenSCAD to facilitate adaptation to other printers.

This is a remix of my previous attempt at this, but improved to include a threaded bearing and with better stabilization of the smooth rods. I saw several designs here for using 608 bearings, but it seems to me those do not hold the threaded rods stable because the 8mm threaded rods are 7.8mm in maximum extent, and it sits too loosely in the 608. This top bracket instead contains a printed bearing piece with internal threads to match the rod and a smooth external surface which spins freely but tightly in the bracket, with very little wobble. The tight grip on the threads of the rod then keeps the bearing piece securely in position vertically.

This results in smoother and quieter prints.

You can spot the need for this sort of upgrade by observing signs of z-axis wobble in your print which have the same pitch as the threads on your rod.

If you're going to install this top bracket, I recommend also installing daks07's Z-axis braces at the same time to stabilize the bottom. http://www.thingiverse.com/thing:1233882 I also recommend that at the same time you take your threaded rod out of the flexible coupler, and wrap a thin strip of aluminum foil several times until it reaches as close as you can get to the 8mm diameter that the flexible coupler expects. This will center your threaded rod in the coupler before you tighten down the set screws, which will also help with stability. (The aluminum foil tip comes from a post I read but cannot find again. Thanks to whoever thought of it.)

Note: The OpenSCAD file uses my threading library for the recessed mounting holes and the threading of the bearing. http://www.thingiverse.com/thing:1686322