Cant get front to back Z alignment

[scyto]

sounds like it might similar to my issues, where the up down movement on the y rails is enough to cause a variance in the first layer height of +0.2 mm in some parts of the build surface. Below is the post where folks helped me figure it out and confirm it. Plus the post of the test i was doing that made me realize i have issues.

Why does an .2mm initial layer measure .4mm +?

Ok, at risk of making myself sound stupid. If i have model that is .2mm high on the z and my initial layer height is .2mm why does: a) the skirt print at .2mm high b) the model print at .4mm high doing this the model only has perimeters, solid infill and external perimeter I am using prusa ironing is off which adds a layer in the slicer) I am using a true micrometer to measure (not calipers) is this one of those conventions like where 2x4 wood is not actually 2x4 inches? am i doing some…

Is a consistent first layer across whole of A350 build plate actually possible?

Now i have solved my sloping bed issues, I continue to try and get the first layer to be the same across the entire build plate. the image below shows where I perceive I am failing. this is the print held up to a screen to act as a light box. The source STL is Bed Level Calibration Square Grid by wsreith - Thingiverse [calibration test] It is printed on a metallic PEI coated plate i purchased ages ago but have not used until today. This gives much better results than the black stock surfa…