Look at the pictures and see my problem

FIally I solved my back pressure problem and Im able to print with PET and an all metal hot end


But I have this issue: there is some kind of waves in the print, but mainly in one of the faces (I printed a box), in the other faces there is almost no trace of these waves. In the pictures you will see waves in the surface, specially where there is those kind of circles. The printing direction was from right to left. What is is the problem and its posible solutions? Thanks in advanced

There can be several factors causing this.
1. Lose belts, or simply not enough tension on them.
2. Lose mechanics, like the springs for the bed being weak and allowing for a swing - this leads to resonance and forms waves.
3. Loose bearings or too much play.
4. Speed and acceleration settings too high - if in doubt check with slower speeds and a simple test object.

I had these waves on my y directions.
After long searches and checking all option I found out that the weight of the bed was too much for belt and springs.
Put a belt tensioner on (springs from some old clothes peg) and replaced the springs under the bed with much stronger ones.

I bet the problem is speed/acceleration... I reduced speed by 5mm/s and the waves improved quit nicely...
Also, could this be related to too much temperature? if the filament extruded is too much liquid could be more affected by vibrations o acceleration?

The springs on my bed are something I wanted to change from some time. Do you know other kind of bed supports/systems? I really dont like this springs stuff, I know that brings some security in case of collision but it introduces a big problem somethimes specially with drection changes

If the slower speed helped it could be resonance as well.
Every speed or direction change causes the moving mass to swing, the more room for this swing the longer the swing in amplitude and duration.
Check if lowering your acceleration and/or jerk settings help to get rid of the ripples.
But also check by hand if you feel any free play in your moving parts.

did you find a fix?

I am facing the same problem and i tried 2 different extruders . one a direct drive and one a geared extruder.. the ripples stay

Yes, I slowd down the speed and reduced acceleration, that eliminated this effect like in 90%. There is sitill some really minor efect, but Im sure it is caused but the springs holding the bed: in a change of direction, while gently touchen the bed, I can feel a very small vibration. When I hve some time I will look for stronger springs o think about how to eliminate them o improve the bed leveling system.