SV07plus - during printing nozzle seems to come down to the printed surface continuously

Hey, i encountered a tricky issue with my printer

When starting a print the first layer is nearly perfect. No scratching, good surface etc.
Sticks good on the plate and does no come up or deform anyhow

After let’s say 4-5 mm height nozzle starts scratching the printed part.

So i fine tune the height by 0.04 mm and no more scratching.

15 minutes later same problem again and again

Had to set 1.25 mm plus on a 35 mm hight printed part.

All bearings seem to have the right tension, nozzle is fixed print head is not loose. Spindles are lubed. Cleaned rails and wheels from dust. I have no idea what else i could try

Does anyone maybe have experience on this?

Maybe any solution?

Thanks for any advice

Picture shows fine tune after z: 6.72 mm print height after several times increasing nozzle distance a few steps

which slicer, and which profile do you use (layer height)?
Is your printer calibrated correctly - if you print a test cube of say 20 x 20 x 20 mm, does it measure correctly after printing? (preferably use calipers)

Hi Tingo,

your advice is much appreciated

I am using orca slicer with SV07+ 0.4 nozzle profile

Layer height is 0.18 mm

i now printed a 20 mm calibration cube, first one was
z 20.2 mm
x 20.05
y 20.03
measured with a digital caliper.

Now i adjusted the rotaion distance values in printer.cfg using a Rotation Distance Calculator for Klipper to get the new values.

I will start a print tomorrow, to see if it still scratches.

Thanks for your suggestions, really hope this helps already.

One more question please, have you ever had the issue that the z-leveling did not work anymore?

In my particular case, the z leveling does not reach the tolerance of 0.005 anymore. It always stops on e.g. 0.03 because of too many tries or of increasing tolerance.

In the near past it always worked well, often better than the 0.005 mm, e.g. 0.002 or else

Best regards