I have built a Cartesian printer by my own design, not much innovation, basically looks like Ultimachine 2 with no middle rods (there are some Chinese printers look like mine). I have 12mm shaft rods on three axis and 12mm ballscrew with antibacklash ballnut.
My prints were giving very small waves along the height. I blamed it to incorrect fixing of ends of the ballscrew. Couple of days ago I designed a new bottom fixing part and replaced the Chinese pillow flange bearing block. Printed a new test cylinder… I want to show you the difference and would like to see you comments…
the cylinder is 15mm in diameter, 0.8mm wall and 25mm high. 1.72 ABS, e3d v6, 0.4 nozzle, 0.2mm layer.
Left one is before, right - after. There are still some waves though, less, but still 
probably, this is a trouble by extruder motor or themperatur control.
interesting to see the seam/spine disappear. did use a different slicing software too? I was using some proprietary XYZware and was getting a spine where the hotend would start and stop on different layers. changed to Cura and I dont see the ends lining up anymore. really nice looking print tho!
I print it ar 220°, can 1-2 degree fluctuation make this? I use MatterControl with it’s own slicer called Matterslice, I think much like Cura. I autotuned now my hotend PID again with filament in it (before I did without), gave different coef.s
@Jules_Hoehn seem disappeared, when I adjusted retract size/speed. when extruding back, it was extruding too much at the beginning. I did not change the slicer software 
any intention to share your 3D Printer design with us?
@Hakan_Evirgen well there is nothing special, I did not think it can be interesting for somebody, I can update this post with some renders and photos of my printer
apparently I can’t do it in the post, I will post separatelly
Was just going to ask how you do that.
let me just make another post with pics