[Solved] Maybe it's just my OCD kicking in - Extruder-head slop?
Just took delivery of a new Ender 3 V2 yesterday, got it built, and after a false-start that looked like something major (but turned out to be nothing) it has successfully printed me the "cat" sample file that comes on the TF card included.
I'm not impressed by WHAT the object is, but I am impressed that the unit seemed to work so well making it. Aside from the fact that it burned up most of four hours, it was pretty painless.
However, I've got a nagging worry.
The Y and Z axes seem to be nice and "snug" on their tracks - They don't bind, but they're definitely tight, which is as it should be - Little/no slop means better accuracy, for reasons that ought to be self-evident. Making them move *AT ALL* takes some actual "I meant to do that" level effort, and is only really possible when the intended movement is the direction they're supposed to move. There may be a TINY bit of play in other directions, but I'd have to guess it's in the neighborhood of 3-5 thousandths, if it's even that much.
The X axis, however, is QUITE sloppy on the rail - I can easily get a quarter inch of motion *in EVERY direction it ISN'T supposed to move* out of it with just a fingertip, never mind actually grabbing on to it and putting some serious force to it. It's almost like the axles of the three wheels are sloppy (they aren't - that was the first thing I looked at - they're torqued down good and solid) enough that they're not "grabbing" the rails as solid as they should (and do on the Y and Z axes).
Is this by design (perhaps as a "minimize damage in the event of the extruder tip crashing into the build plate/other obstacle" measure) or am I needing to be looking at tearing the beast down trying to find where the slop is coming from? It can't POSSIBLY be any good for the accuracy of the beast.
Answered perfectly in the vid connected to the post here
Never had a clue that such a thing was in use on these beasties, but makes perfect sense.