The K8200 is an affordable 3D printer kit for PLA and ABS filaments. I got my kit 4 weeks ago and it took me 3 evenings to put it together. While the engineering and especially the manual of the printer are very good, it also has some pretty annoying shortcomings which you'll have to correct in order to get good results (and they can be very good indeed). The most important are:

• The belt pulleys for the X and Y axes are horribly wobbly. You'll have to print yourself decent ones (e.g. using this thing) to achieve accurate X and Y resolution. The first picture shows the difference. The blue gauge was printed using the stock pulleys, the black one with the new pulleys.

• The M8 threaded rod for the Z feeder is crap. Since the coupler between the Z motor and the rod is wobbly too, you'll get all sorts of inaccuracies in the Z feed, resulting in a inhomogeneous layer thickness and ugly side walls. The solution is to replace the M8 rod and its nuts with a TSR-Tr8x1.5 trapezoidal-thread spindle and matching nuts, thereby greatly increasing Z resolution. The picture with the robots again shows the difference (white: M8 rod, black: Tr8x1.5 rod). Note that you'll have to patch the firmware too since the slope of the thread is different.