This is my attempt at reducing Z-Wobble on the K8200. There is more detail about the concept and additional hardware needed in the instructions.Additional hardware needed to build this: 2 x 30mm M10 steel washers 2 x M8 steel nuts 1 x M3 bolt, nut and washer optional: 2 x M8 plastic washers 2 x M8 steel washers The stepper mount used in the picture is http://www.thingiverse.com/thing:443084, and it can't really hold the weight of the Z axis securely, so the threaded rod is suspended by http://www.thingiverse.com/thing:443103. When assembling it is better to tighten the threaded rod/stepper adapter last, so that the weight is entirely supported by the upper bearing. This thing is partly inspired by http://www.thingiverse.com/thing:304424, but the anti-backlash spring on that part is not really effective since it only pushes one nut against the other while leaving the frame unaffected. I had two 30mm wide M10 washers handy, and I thought this would give me a more regular surface for the driving nuts to slide on than a printed PLA surface. In my build I am using nylon M8 washers backed by steel M8 washers to ensure the thing is sturdy, but I bet that a printed M8 PLA washer will work just as well to avoid having a metal/metal sliding surface interface. My build is definitely overkill, but I had all the bits, so why not use them? I didn't have a suitable spring, and since winter is a few months off I don't have a discarded umbrella to cannibalize.To overcome that I designed a PLA spring that can be printed in several sections to be stacked. For the original dimensions you will need two prints of part a and one print of part b (part b has a small step that holds the upper washer frame in place, which in turn keeps the spring centred) The nut holder will also have to be printed twice. Several parts have to be flipped upside/down in order to print easily without support, the STL files show them in their assembly position. the mounting block, spring parts, upper washer frame and nut holder all print better upside-down. When assembling it is a bit difficult to get the spring to push on the upper washer with the right strength, It may be necessary to rotate the nut in the nut holder by a fraction of a turn, but in order to do that it has to be removed from the thread, so it is probably a good idea to temporarily mark one spot on the nut with a permanent marker.