[bo.gardmark]

Does anybody have an opinion or experience of the variation of the Z-height as a function of the position of the Y-axis?

Below is a graph. The Z-axis height is measured relative a reference surface plate (with an accuracy of 2.8 microns). As can be seen from the graph we have an almost sinus shaped variation of the Z-axis height. The period of the “sinus” curve matches the pitch of the Y-axis leads screw. The variation is about 5 microns at max. Is this (sinus shape) normal?!



The CNC router is a type with a gantry. See photo below. For the sake of clarity, my primary use is for PCB etching.



Regards

Bo

[Zig]

Typically recirculating ball nut screws have a cyclic nature usually associated with positional error along the length of the screw.


The cross axis coupling You are experiencing may be due to a small degree of eccentricity ( rolled screw versus ground screw?) and too compliant a machine frame? bearing system where the screw is affecting stresses in the axis and causing the tool tip to oscillate.