It's got a new x-end idler. This one http://www.thingiverse.com/image:63587, but instead of fitting real LM8UU linear bearings, I've fitted these printable PLA substitutes http://www.thingiverse.com/thing:12238. We'll see how that experiment goes!
Now, just to mix it up a bit I've put the more traditional x-end motor bracket, http://www.thingiverse.com/image:63177, on the far end, but I've modified it slightly. I'm only using one nut on the z threaded rods. Can't see the point of the second nut and the spring between them. I know it's an anti-backlash design, but I've had only one nut in my wooden design and gravity looks after backlash in the vertical direction. I've no plans to print in zero gravity. :-) Also I couldn't bring myself to use that overhanging motor design, so my motor stays inboard for a more balanced look.
http://www.thingiverse.com/thing:11220. I had a steel rod coupler, seen here, but was so rigid it exaggerated imperfections in the threaded rod, resulting in motor and x-axis wobble. The new arrangement is much more forgiving and visibly smoother as the x-axis assembly moves up and down.
I've retained my wooden z-motor brackets and vertexes(?). They are solid and accurate.
The x-carriage and extruder is now fully RepRap, and as you can see from the part on the bed, I'm printing a spooler!
But a key part of improving print quality has been a fresh examination and fine tuning of basics like squareness, perpendicular z-rods, frame triangle distances all equal. I've screwed the unit to a base board to increase rigidity also. Finally, the introduction of better belt-tensioning technique such as found on Gregs x-carriage, and this little unit (http://www.thingiverse.com/thing:10274) have been invaluable in removing print quality issues due to backlash. The use of these fine tuners allows belt tension to be adjusted a little at a time without over tightening, that might strain something else out of alignment.
Here's a quick look at two test pieces fresh off the newly rebuild rig. I'm pleased with the current print quality.
Now to make it go faster! :-)