[Surface Quality Downward Spiral. 6 months and still cant figure out.]

Dear Community.

3D printing seemed pretty straight forward to me until I hit this never ending downward spiral.

I have been printing super-quality objects at 0.6mm nozzle with a 0.4 mm tall layer.

Until I started obtaining this:

Cooling problems? Seems not, as I have refurbished the cooling system and obtained same results.

Under extrusion? Changed EVERYTHING, from tubes to nozzles to hot ends to stepper motors. First print (if lucky) turns out messy yet not devastating..

Bad speed/heat combination? Don't think so, as printing in PLA I range from 220 C for 30.35mm/s to 215 for 25mm/s.

Maintainance? I regularly oil all axis.

So I changed nozzle size to 0.5mm and layer height to 0.35mm.

This is what I'm getting:

The surface seems trembling, as if the structure weren't rigid enough.

Its been 6 months of testings and now I'm at a dead end.

Cannot find any more specific threads that could solve my issue, as now it seems extremely peculiar to me.

Looking for suggestions on how to move on this case.

THANK YOU

Some INFO:

PLA

UM2

30mm/s print speed

2mm retraction

2 outlines (shell)

100%-120% extrusion width

100% flow

50C bed

215-220C nozzle

Any more info please ask