printrbot plus top connecting bar

you can add this to the printrbot so the z rods become connected, they restrain the screws by keeping them vertical, this works better with a screw isolator like this: http://www.thingiverse.com/thing:40272 to avoid any problem caused by a non-straight screw or any misaligment.
i designed this for a 9.5mm horizontal rod i had lying around, i am providing the files so you can change the diameter to the one you prefer, or you can ask and i will upload it for different rods.

this works with t