Horizontal banding

I just spent lot of time trying to understand why I got horizontal banding on new parts with oboXL3D printer. Initially it looks like this:
:

 To compare with another print coming from Kossel printer (the orange part)

After many tests and assumptions like bad threaded rod on Z or not aligned, accuracy of XY, bad filament, bad heater, etc... I finally found the solution, thanks to a post found on a forum.
That post explains that this type of banding may come from the regulation of head bed temperature.

So, I followed the instructions and did this:
1/ uncomment #PIDTEMP Bed in Marlin configuration.h, to activate true PID regulation of the bad, instead of basic regulation (as defined by default)
2/ add correct values Kp,Ki,Kd (as computed automatically by Marlin). 



And it gave this, (on the left before tuning, on the right after tuning):

Thanks to those posts:
https://ultimaker.com/.../7907-horizontal-banding-on-um2
https://ultimaker.com/.../7613-firmware-surface-kwality...