Had some issues wiith my core xy printer an annoying mirror of y axis on prints.
In general was not an issue on 90% of the prints , just when you print for hours and you realize that you forgot to mirror the part in the slicer and the writing is backwards.
Issue is corrected now -so this sphericube was designed to verify any other potential issues.
Designed hollow to minimize material consumption and reduce print time.
You also could use to check again your calibration 30 by 30 by 30mm.