The first test print on my assembled Creality Ender-3 V2 showed some artifacts. General symptoms are that some layers look squished and overall height is lower than it should be.
These two parts were the same 3D file on two separate print jobs. The piece on the right was printed before my modification, showing many problematic layers and the overall height is lower than it should be. Hypothesis: my Z-axis is binding, occasionally failing to move the specified layer height. Verification: With motor powered off, it is very hard to turn the Z-axis leadscrew by hand.
This put the Z-axis motor mount under scrutiny.
Looking closer, I saw it was not sitting square. There is an uneven gap forced by the motor that is slightly fatter around the black midsection than its silvery ends. This means when the motor mounting block is tightened against the vertical Z-axis extrusion beam, that motor rotates and output shaft tilts off vertical.
A tiny gap would not have caused a problem, because the shaft coupler could translate motion through a small twist. However, this gap is larger than the shaft coupler could compensate for, causing it to bind up. I saw two ways to reduce this gap. (1) Grind the side of Z-axis stepper motor to eliminate the bulge, or (2) insert a spacing shim into the motor mount. I don’t have a precision machining grinder to do #1, but I do have other 3D printers to do #2. I printed some shims of different thicknesses on my MatterHackers Pulse 3D XE.
I tried each of those to find the one that allowed smoothest Z-axis leadscrew turning by hand.
After this modification, the print visual quality and Z-axis dimensional accuracy improved tremendously. The piece on the left was printed after this modification.
So that’s my first problem solved, and I think this printer will work well for the immediate future. However, looking at how it was built, I do have some concerns about long-term accuracy.