Ender-3 Irratic Extrusion Issues

[ExDex]

Hello All,

I am dealing with what looks like under-extrusion issues with a modified Ender-3. I have recently upgraded the main board with the MKS-Gen-L v1.0 and the latest Marlin firmware. I have installed the BL-touch and upgraded the the extruder to the Creality metal extruder; replaced the bowden tube with a Capricorn; and the bowden tube fittings with higher-end units that have eliminated any tube slippage; and the hot-end with the Micro-Swiss all metal. I have confirmed the hot-end temperature is accurate using a thermocouple. All PID values have been generated for both the hot-end and the bed, so I am confident that the printer is thermally accurate. Many things have changed and all seems to be working well individually.

I have a clean install of Cura 4.6.1 and am using the default settings for "Standard Quality - 0.2mm" and the default settings for Generic PLA filament. The filament used is 'Solutech - Teal Blue'. I have tried the same print with an 'AMZ3D Silk-Silver PLA' with much worse results. The AMZ3D filament has been reliable in the past, and I tried the print using this filament to eliminate the Solutech filament from the equation.

Current settings are 200 degrees for the hot-end and 60 degrees build-plate. I have repeated the print with hot-end temperature settings of 195, 205 and 210 degrees C. Quality did change, as expected, but the underlying gaps in the print remain. The extruder does occasionally pop, but the filament flows freely. I do not suspect a nozzle blockage. I did try to increase the flow to 110% and 120% with no noticeable improvement.

From the symptoms it appears that the nozzle's motion is not always parallel with the previous layer of the print; sometimes pressing against it and blocking the flow of filament, other times leaving a gap. Suspecting a flat spot in the gantry rollers, I replaced the wheels with a new set. There have been grooves worn into the tapered edges of the delrin wheels which indicated some wear. If anything, this made the problem worse (worse even from the attached photos).

I added the gcodes to perform a 6x6 point automated bed level prior to starting a print. A test print around the perimeter and through the center of the print indicated that the levelling seems to be good. One thought I had is that the ABL is compensating where it shouldn't.

I am running out of ideas... any suggestions would be much appreciated.