What Can Cause Z-Offset to Shift?

So sometime back I started to have issues with my z-offset. This ended up happening because my filament snagged, at least from what I could tell because on both occurrences, after this happened I noticed a change.

Since then the issue has never occured, and I thought I had my offset dial in almost perfectly. But recently it seems once again I have to lower it more, and can’t figure out why. I haven’t had a snag!

Only two things have happened since then

  • I had to do some sanding with like 3200 grit and some Acetone and Water + Alcohol (1 to 10 mixture) to remove a really stuck on ABS residue

  • The z rods (threaded) are STILL grinding/buzzing a little here and there. Back when a snag happened these got off and I had to loosen the mounts to manually turn then and line them back up. They seem fine, but the left will buzz, ONLY when raising it (where I also am having the worst adhesion). Although just this morning I measured the lengths, and they seems almost even.

There was one other thing. After I got it really low, where it was a SOLID first layer, I raised it back up a bit as it was adhering a little more then I liked. But after some failed prints, and undesired results, I lowered it back down to where it was, numerically. But it’s not actually printing the same. I am now getting visible lines, and the back left corner (same side the rod buzzes going up, and I keep trying to just slightly move it, might have finally done that this last time) is having adhering problems.

What is causing this? Are the brackets that ride on the threaded z-rods not tight enough and they are slipping? When I adjusted them I was told not to tighten them too much

If this is a Taz 6, its likely the auto-level is off due to any of the following:

  • dirty wiper pad
  • dirty leveling discs
  • dirty nozzle

Some other things to consider:

  • agressive part removal
  • loose toolhead
  • loose x-carriage
  • loose z-coupler

It doesn’t take much to throw off the z-offset of the nozzle… .1 or .2mm will make a noticeable difference in the bottom layer pattern.

This will throw your motors/rods out of level. The buzzing means it missed a step. Too much binding will cause step loss.