Ender 3 Inconsistent Layers

[uromastix]

Hello, I have been troubleshooting this issue for a few months now. My prints look "ok" when in the right light but if you shine a light down across the layers a pattern appears and shows inconsistent layers. It does not appear to be periodic. I am getting these big bulges at the same point (across z-axis) across the whole part. Along with small perturbations across the z-axis as well. I don't think these are the same issue because with the little lines, the thickness of the outer wall seems to vary throughout an entire layer while with the big bulges it seems like the entire layer is squashed.

Below compares between parts printed with different extruder methods. Orbiter looks a little better so I'll print on that from now on. Large bulges are highlighted in red.
zesty_vs_orbiter.jpg
Below is a highlight of the issue with a 3d part on the right and a single walled cylinder on the left. The large ones are harder to see on the one walled spiral cylinder since there is less plastic to compound the issue at that point in the z-axis but its there.
cylinder_vs_3d_part.jpg

After this I suspected a z-axis issue and I took my lead screw out and adjusted the concentric nuts which hold the x-axis gantry to the frame 'till the axis moved up and down a bit better and now those big bulges are smaller, and the little ones are still there. Below is a before and after of that adjustment.
c_nuts_adjusted.jpg

My current setup is a stock Ender 3 excluding:

• BTT SKR 1.2 mini (TMC 2209) with LCD touchscreen
• Orbiter extruder
• EZ ABL
• Meanwell PSU
• Microswiss all metal hotend
• Eryone PLA filament
• springboard steel magnetic buildplate with PEI sheet
• new extruder heater cartridge and thermistor

Things I've tried:

• Changing the control board(BTT skr 1.3 -> BTT skr 1.2 mini)
• calibrating the extruder steps a million times (with digital calipers)
• changing the extruder method (Zesty to orbiter)
• increasing airflow over the heatsink to fix heatcreep
• take the z-axis lead screw off and cleaned it and relubed it with some silicone teflon lube and also rolled it across a marble table to see if it was wobbly and it seemed straight
• adjusting the brass leadscrew nut mounting bolt tension
• adjusting concentric nuts so that its tight but not too tight and testing prints with various tightness
• changing the PSU (stock to Meanwell)
• adding TL smoothers to extruder and z-axis steppers
• changing slicers (PrusaSlic3r and Cura)
• PID calibration for heated bed and nozzle

I'm open to trying anything, even the same thing twice. Currently thinking about getting another z stepper for a dual z stepper setup :shrug:. Open to any input on this issue as it's driving me mad!

Thank you!

[Martin_au]

Have you measured your filament diameter? I've just effectively binned (well, I'm using it for fun stuff, not for anything critical), a very nice matte filament that looks great, but has widely varying filament diameters. Similar issue, wonky and irregular layers. IIRC, diameters for that filament ranged over about 0.1mm, which translates into around 10% volumetric change.

[Gambo]

The other thing that is worth a look at is belt tightness !