Solved This is what happens when your z rods fall out of alignment.

SO.. had a bit of typical luck. Broke my hex head. Replaced it with a different but same nominal length extruder that works fine... for the time being.

Anyway.. since I've replaced the hotend, I can't get the thing to print against the bed.
It G29s then moves to center. Bops up 1mm and starts printing.
this would seem to be software problem. Is that right? I'm using s3d. Changed my first level thickness and it does nothing.

Do I not understand G29? I think I should be able to put any size nozzle on it (and have) and make it work with a G29. Sometimes it doesn't work... where's the ghost?

 

OK.. FIXED

Turns out the Z screws were not "aligned". That is. one was turned without the other. They were off a mm or 2 and it was screwing it up.
I've had this problem before and managed to fix it by adjusting the rods to be equal again.

just noticed that when it was at 0 it wasn't dragging on the bed. One switch was depressed, the other side wasn't. Must make the G29 grumpy. Nevermind the obvious problems with misalignment of the z plane.

 

Question:
1. Any idea what caused the Z screws to become not aligned
2. What would stop one rod from turning
3. How do you adjust the rods to make them equal

 

1. Messnin around with the thing when off. replacing wiring, turning it upside down, intentionally turning them.
2. Being turned off. Forcing them. Moving them when unlocked, going over the maximum height.
3. eyeballing it is really good enough, as long as the microswitches both engage, it seems to work out. but I have put calipers on them before.

there's nothing joining them together but logic. any rotation of one without the other is misaligning them. Mine used to turn in unison while powered but unlocked, but I think since adding a light and fan, lcd controller, maybe whatever system that was intentionally or unintentionally doing that isn weak. Maybe I hit a pot? whatever.. it prints fine if its not effed with.