This is my design to avoid wobble on the hotend caused by a not straight z-rod. This thing avoids both wobble and nut backlash by isolating the x and y movement of the z-rod. Of course you can solve all these problems by buying a very G$$D quality z-rod. :-) Z-isolator in action: http://youtu.be/Ix8PHHisDuwThe entire systems is composed by 3 modifications and 1 optional improvement, more details on the images.