I dont know what to call it problem.
At the outset I hope i can post about the printer which is a Custom DIY Bear Prusa and not original i3. If not I request the mods to take appropriate action.
So when I first assembled the machine I had this weird ringing kind of issue along the Y-axis. Its not exactly ringing since my guess is that it is not related to any harmonics. One day while I was tuning the firmware and tightening the screws it magically disappeared. I dont know what caused the problem and what resolved it. So everything was fine for some time and printer was printing well.
Yesterday i decided to change the glass bed to spring steel PEI coated bed and also to grease the Z leadscrews and X-Y smoothrods with superlube. And the problem reappeared that too along both X and Y axis as can be seen in the picture.
So far I have tried:
1) tightening (or loosening) the screws holding the POM nuts
2) tightening X and Y belts
3) Different print speeds upto 50% lower
4) Z leveling of leadcrews
5) Extrusion calibration
6) Lowering the TMC2209 XY motor currents (SKR 1.4)
The first few layers seem to print normally. after that the ridges appear along the X and Y axis periodically.
Any clues as to what could be the issue?
RE: I dont know what to call it problem.
Ok so it turns out that the problem is called Z banding. In my case the problem turned out to be the bang bang control of heat bed temperature. Changed to PID in FW and all is well. How the bang bang temperature control results in the Z banding is beyond me though..