Do I need to adjust z-offset after putting on thicker PEI?

I just put on a thicker PEI after my old PEI surface started to bubble.

My understanding is the z-offset is the distance from the BL touch to the nozzle head. If this is true I should not need to adjust it if I change the PEI to a thicker material, as the bed doesn’t affect this offset…that is unless I bumped the the BL touch or changed the nozzle.

Is this correct?

Well, just to be safe, I did a test print. Even though the PEI surface is higher, I did not need to change the z-offset.

I would always double-check it. But with a typical standard thickness of a 1st layer (assuming you are running the 0.5mm nozzle) a first layer might be anywhere from .25 to maybe .35 and that’s enough breathing room that a small extra thickness of the PEI shouldn’t cause any harm.

I inspect the quality of the first layer to make sure there are no gaps between filament rows (extruder too high or under-extruding) and that the filament rows aren’t so close that the filament is bulging up where the rows meet or if you see wrinkles in the layer (extruder too low or over-extruding).

You can also peel off the skirt layer and measure it using calipers to make sure it’s reasonably close to the expected thickness. Don’t obsess … it wont be perfect. E.g. if you ask for .35mm first layer and what you measure is more like .33 … that’s probably close enough. Measure in MANY locations. It will vary from measurement point to measurement point.

Thanks Tim. I measured a disk (that I think you or bmorgan taught me) and it was supposed to be 0.4 but I got 0.45. Otherwise it looks good. A little bit of an elephant foot if I use a magnifying glass. I might adjust my z-offset slightly, though the first layers look good now that I got my e-steps programmed correctly. It was off by 1.5 %.