Solved Z wobble but just on one side

Which makes me think it isn't wobble?

I'm trying to chase this down. I have left side ribbing. right side looks fine all the way up, left side is uniformly (that is from bottom to top) randomly ribby. Which makes me think its not Z axis related because it stays pretty uniform all the way up. I would expect a Z axis stability problem to get worse as it went up.

Looks like it pretty much starts at X0 towards negative and corrects to pretty again at X0 on the way to positive. no clearly defined line or anything, rows to worst at the apogee of x axis in that direction.

Could it be simple as a cocked x axis? probably not.

I just noticed its not X0 its relative X0, so if you have 2 pillars, side by side, they will look identically ribbed on the left

 

At work, but printing a test tower as i left.

What causes over shooting? X slop? Seems like something like that. Have to do a test circle too.

 

Looks like my y axis stepper is slightly bent. but its probably been that way forever. I can feel it pulsing slightly when i pull it back and forth by hand.
Not particularly happy with my test tower. The ribs around it are not the same on all sides, which has been my experience in over extrusion. Definitely nicer on one side than the other 2 or 3. HMMMM.

I can't find anything wonky with the machine other than that slightly bent y axis stepper. Is this just bad E-steps? I use so many different materials and they all act a little differently.
Looking back at some recent prints it wasn't there a couple weeks ago, it was absolutely NOT there. I'll keep poking around, but any ideas would be appreciated.

 

Tightened everything, cleaned everything, adjusted a couple things.
printed a tower in PET at the same speed; it was considerably better. Think my tower layers were partly extrusion centered, need to drop it .. maybe 5% for PLA. Which is strange, since it seems that the hobbed bolt digs in further on PLA. More expansion when melted?

 

that WAS slowed down significantly. Since the whole thing was perimeters (2 layers wide). I printed a PET one like I said. Makes me think I may have had something loose (and found it without knowing) and my extrusion is bad for PLA.

I'm not down to fine tuning, I'm back to fine tuning. I was tuned. I have a bowl sitting next to me I need a jewelers loop to see layers in. But that was 2 weeks ago. I whacked something I figure.

 

as usual, thanks for the input.
my y axis was running loose(er than it should have) ever since I got it. about 2 weeks ago, i had a print shift a tooth or so in the middle of a print.
I took it apart and cinched up the belt. since then, it started squeaking when moving slowly around the middle. I think I may have over tightened it. Also, the belt was riding high on the idlers (pinions). Today I took it back apart, replaced that cog (it looked out of round, but it appears to be the stepper) and lowered the cog so it would ride nicely on the pinions. I have a few meters of belt, but that one didn't show any signs of wear but for a bit of rubbing on the top.
I also checked torque on pretty much everything and honed my Z axis support a bit. Second test tower looked much much better. cant see any ribs nor can my fingernail catch any. But it was not in the same material. May replace that Y belt tomorrow.

I'm printing a statue (classic 3d owl) scaled down for economy's sake, i'll see if a real world type model reacts differently than my test tower, or if it starts going off again after some time.

 

hey so is ther supposed to be a cut in the y axis motor shaft like the extruder shaft? mine's round... though it seems plenty tight.

 

I just fixed this on my printer, your Z rods could not straight. I don't know if the cause is the same, but my Z stabilizers were too long and bending the Z rods inward. After I took the stabilizers off and kept it slow the lower and upper banding went away!

Printer adjustable ones now

 

well I think I must have found the loose thing. this last print came out pretty well.. except for the absolutely horrible ringing. And it's a bit hairy.. but that's how PET goes.
From what I understand, that is internal to the stepper motor right? Like.. it bouncing on the em field trying to maintain its position?

If that's the case maybe I have a less than stellar X axis stepper? I just can't bring the ringing down to zero no matter how slow I go. and "normal" speeds, its the main feature.

That's 3600mm/min with 50% underspeed for outlines. The outer perimeter is downright slow.