The documentation for pressure advance suggests that the layer height be 75% of the nozzle dia (which is 0.4 mm in my case). Does this apply to the first layer as well? If I keep the first layer at 0.4 mm to improve bed adhesion, would I have to enter the start = 0.4 - 0.3 = 0.1 in the formula calculation?
I assume that you are referring to Pressure advance - Klipper documentation and the formula
pressure_advance = <start> + <measured_height> * <factor>
Some comments:
- The
<start>value refers to your initial Pressure Advance value. This means you could do a test starting at PA of 0.5 and have it run until 0.8 to closely inspect this interval. - The test results are not so selective or distinctive that it would matter if your first layer is 0.4 instead of 0.3
- Rule of thumb to choose the right value from the test object: Rather go to a lower value than a higher one
- Last but not least: The need to use 0.4 as first layer height to secure adhesion indicates that you have other topics that should be handled first: bed planarity, bed leveling, print surface, print temperature etc.
Thank you, this helps. The bed is a machined 5052 plate with a PEI sheet on it. I did a Z-TILT_ADJUST which aligned the two Z-steppers to within 10 microns tolerance and then a BED_MESH_CALIBRATE after this. I don’t think it gets any flatter and level than this 
For some strange reason, with a layer height of 0.3 mm the first layer wouldn’t stick to the bed but other prints with the same layer height usually do which is what threw me off.