Z offset not even close

[WayneManion]

I have Klipper mainline installed on my SV08. I have acrylic side panels, but no other modifications. No doors, no top.

I typically fire off prints remotely. I had a string of bad prints. There were layer shifts of just bad bed adhesion. It takes a long time for this printer to prepare to print so I didn't want to sit down and watch it in person. Here is a picture of some test patches printed without babystepping:

So last night I had some free time. I started a print with 25 test patches. I used my phone to baby-step the printer, and I had to move it down by 0.9mm to get the patches to stick. When I started, the z-offset in fluidd said 1.0mm. When I was done bumping it down by 0.05mm at a time it said 0.1mm. The patches were finally sticking to the metal plate. (Screenshot taken with printer idle)

I repeated this process but after the first patch was trash, I bumped it down to 0.1mm as fast as I could. After that all remaining test patches were good.

I updated KIAUH, Klipper, etc. this morning. I installed the printer config (except the MCU IDs of course) from this repo. Again, the patches are trash unless I manually bump the z-offset down by 0.85-0.9mm.

If I change the value of offsetadjust in saved_variables.cfg from 0 to 0.9, should I expect this problem to disappear?

[Rappetor]

I assume you mean the offset is quite off after using the Z_OFFSET_CALIBRATION command? But yes, that is why the offsetadjust exists so that should be the correct spot to make adjustments (for the Z_OFFSET_CALIBRATION script).

If you needed to move down I think the value should be -0.9 then (negative) right? If you are cautious you could start with half the value and check if it only needs half the adjustments now.

[WayneManion]

OK, that's what's I thought. I wanted to ask first since it didn't say zoffsetadjust.

I don't think changing it by half is really going to help. The results were equally bad when printing 0.9mm too high as they were when printing 0.45mm too high. It was really only in the last 0.1-0.2mm of downward adjustment when I started seeing any real change in the results.

Would you care to speculate on why the offset value is so high for me? Do you have a non-zero z offset value set in saved_variables.cfg ?

Thanks.

[Rappetor]

Half way was more of a sanity check to see if you are going the right way with the adjustment and not having the nozzle dig into the buildplate after perhaps making a step too big 😄 As a quick test (without printing) you can always do the auto calibration and then do a paper test at z=0 or something.

Not really sure what could be causing the difference though, perhaps difference in tolerances of the pressure sensor or the inductive sensor? Also it has been stated by some that the inductive sensor might give different results on the buildplate vs the pressure sensor (difference in material and/or thickness). So who knows.. It's certainly not a 100% foolproof and 'factory ready' solution because most people need to apply some changes to the auto z. (in the script Sovol already makes a 0.75mm change by default as well)

But as long as it's consistent you can apply the difference with offsetadjust and fix it with that.

Originally there was actually a custom script (via the display/lcd interface) to babystep the z offset and then it would save these changes to the offsetadjust in the saved variables (but not in all the offset menu's mind you..). However since we have removed all the scripts this doesn't work anymore. Their method also caused a lot of confusion with people because changes made via the lcd/display would stick when doing the auto z calibration again. But changes made to the z offset via e.g. the mainsail interface are reset when you do the auto z again. So while people thought they were changing the same thing they were actually not.

I'm almost 100% sure this was the cause for all of the reviews in the beginning to have weird first layer issues.