DX Z-Auto off by 0.3-0.4mm: Reason found, no Solution?

Snapmaker 2.0
1

I think several of you reported that after using the DX’s Z-Auto-Calibration (which is really cool!) the Z-Offset is ~0.3-0.4mm too high, and when running the actual print, you have to manually lower the head. I certainly have this. Watching the Auto-Z-Calibration, I could see that when the head presses down on the print bed to trigger the force sensor, the head visibly flexes up. This is now even more pronounced with the quick swap kit installed, increasing the lever length. I today dismantled all five linear modules and adjusted the carriages according to this procedure: https://support.snapmaker.com/hc/en-us/articles/1500000110341-What-should-I-do-when-the-slider-of-the-Linear-Module-comes-loose- (all were off by ~0.3 mm), because I saw a remote chance that the play in X and Z might be responsible for the flex, but even with properly tightened bearings, the flex is visible. I yet have to run a print, but I guess it will be off again.

So what’s the solution? I’ve no idea, how the force-sensor works, if it is an analog sensor where firmware could be altered to trigger at less pressure, or if it has a fixed trigger level. If the former, Snapmaker could adjust firmware. If not, I guess I’ve one reason more to do some of the rigidity mod’s several users have shared here…

EDIT: Just ran the X/Y calibration print, and had again to adjust by 0.3 (left) and 0.35 (right).

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2

Great finding! Thanks

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My workaround is to lower the z-offset calibration.
This needs to be done with each extruder.
I lower it to the calibration card, then get it out and lower the head by additional - 0.5mm.
After this procedure i calibrate the bed and it seems working, i only need to lower live z offset by - 0.1 to - 0.2mm.

Note: my nozzle is not pretty clean at calibration so the offset comes maybe from there…

Otherwise sometimes i get problems in outer areas where i cant lower the live z offset below -0.5mm.

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4

That’s clever… I assume that this is “only” possible with manual Z calibration?

5

Not sure how to understand this.
I do not calibrate the bed manually, i do it in preheat auto mode.

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Sorry, was not really clear. Four things influence the Z-position of the DX:

  • Sensor calibration
  • Z-Auto/Manual adjustment
  • Bed leveling
  • On-the-fly Z-Adjustment

At which step do you “cheat”?

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Hey, i cheat at sensor calibration to get rid of the permanent -0.3mm (at least) live-on-the-fly z offset.
This works only if you do a bed leveling afterwards, it seems the current grid is not affected.

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8

Didn’t verify but the dualextruder probe seems adjustable:

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9

Just uploaded some photo’s so its more clear what the HelpDesk said

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