This is my alignment on a cylinde constracted from points on Z axis at -19 / -21 / -23 as Z coordinates. Keep in mind that I have points at around 60 degs on the left and another 60 degs on the right "forming" incomplete inner part circles since there is material missing north and south side of the part. This is my datum and seems to be consistent as a cylinder both at cylindricity and diameter.
In any case. I have 6 "semi" circles on the outside to form 3 circles ( I am probing left and right again of the part) at Z values -5 / -12.5 / -18
No problem with their circularity and diameter either. The issue comes with the repeatability of the circles that are the furthest away from the probings of my datum A, meaning circle -5 and -12.5
The -5 one has terrible repeatability in terms of true position with 0.03mm range of measurements. This is not the case with my circle at -18 which is constructed with the same logic and it is basicly the same tool that is creating it in the CNC machine and same probes and everything in CMM.
What am I missing? Where is the mistake? Could it be the level on a cylinder and how the 2d circle is projected? Does this justify the dispersion? I am not moving the part between the measurements and all other locations / positions / features are consistent.
Thanks in advance for your answers and time.