Edit 14/04/2017 - Added a 46mm version
Edit 08/04/2017 - Deleted the old files and re-uploaded new files which no longer have the graphic glitch which showed one of the M4 screw holes covered over. Also remixed the gap between the rod centres to 45.5mm and 45.75mm which were requested. Also uploaded a .step file of the original so others can edit themselves. The original has 45mm between rod centres.
Edit 17/03/2017 - I added a .step file which I converted from the original .stl file so it's not perfect but it is now easier for others to remix for their machines.
Edit 14/03/2017 - I added another version of the X carriage with an extra 0.25mm separation between the bearings which should allow for smother movement using Igus Drylin RJ4JP-01-08.
I (along with others) found that the newer Anet A8 from late 2016 to Jan 2017 on wards had slightly different dimensions between the 2 x axis guide rods. The original prusa rework x carriage was very tight fitting especially towards the ends of the x axis travel range.
I have expanded this x carriage by 0.5mm between the top and bottom bearing housings to allow for this. I have found that with LM8UU bearings the fit is perfect and there is no slop at all and no binding.
To remix this for Igus bearings which have much tighter tolerance's then LM8UU bearings it might have to be expanded by another 0.5mm as I found that my printed PLA Igus replica bearings were still a bit tight on the ends of the travel. I will experiment when my Igus bearings turn up.
NOTE: Yes I am aware that one of the M4 screw holes has one end covered. This was a bug that I can't yet rectify in Fusion 360 after I split the body in two. When you load the .stl into your slicer it should go away and leave the hole open.
Best printed slower for more accuracy. I printed mine at 30mm/s with 20mm/s outer wall.