this post was submitted on 26 Jun 2023
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6
Wandering z-offset (self.3dprinting)
submitted 2 years ago by Physicraft to c/3dprinting
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I've got an Ender 3-pro with cr-touch and plastic washers instead of springs. I sanded down the washers to manually level the bed to var of 0.372.

When I adjust the z-offset it prints great but I need to adjust it before every single print. It stays within a fairly narrow range, -1.11 to -1.37 but if I don't do that adjustment, the print usually fails.

I preheat the bed and nozel before adjusting it. None of the screws seem to be loose. The nozel doesn't jiggle around. I tightened down the screws for the z-actuator.

What else could I be missing?

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[–] [email protected] 1 points 2 years ago* (last edited 2 years ago)

So … are you using marlin?

Id recommend setting up UBL with the cr-touch. This will let you probe the bed and record a mesh (which you can then set up to fade back to flat/level).

Then, in your start code, load that mesh and do a 3 or 4-point probe to adjust the tilt of the mesh plane.

You have to flash new firmware if it’s not, I recommend probing as many points as you can to generate the mesh- this is mostly dependent on your board and it’s onboard storage. (Check to see if your board has onboard. I forget what the ender 3 pros have.)

Once UBL is set up,

  • Saving a mesh is simple: calibrate z height if you need to,
  • g28 ; to home everything.
  • g29 p0 ; to purge/delete the old mesh.
  • G29 p1 t ; to start the probing process
  • g29 p3 ; will generate approximations for probed points it
    couldn’t reach, imo it’s good enough on its own there’s really no need to manually fine tune.
  • g29 s0 ;saves mesh to slot 0.

If you have no storage space, you’ll have to use mesh leveling which will repeat this process for every print. (Tedious)

I use pronterface to do this, you could use any direct-input that returns a reply back (octoprint works. Cura does not.)
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My calibration for z offset consists of:

  • zeroing the z off set (m92 z0)
  • setting software endstops off (m211 s0)(be sure to turn them back on with m211 s1 when done.)
  • moving the nozzle to the center, the same point just probed and coming down until you’re favorite feeler gauge is touching- sheet of paper, an actual feeler gauge. Whatever.)
  • read the current position (m114)
  • use the z position from the last as the new value for offset (m92 z-2.1 is my current offset, for example.
  • seriously remember to turn software endstops back on (m221 s1)

I then rely on tilting the mesh to accommodate any slop in the bed’s leveling- as long as it’s visibly square ive not had a problem. I suggest springs over stand-off washers…Mostly because this allows some give in the build surface if you start dragging… and because plastic washers (or any washers, really,) will deform anyways over time.

The relevant start gcode I use:

  • g29 a; activates the UBL stuff
  • g29 L0 ; loads the mesh stored in the zero slot
  • g29 j3 ; tilts on a 3x3 grid. It will align the mesh to this plane
  • g29 f10.0 ;fade height, it doesn’t have to be super thick. It adjusts the initial layers across this height to come back to flat.