MCG tools analyses the form error of the sphere that is generated by the MCG arm around its pivot in order to identify six of the main CMM geometrical errors: three squareness errors and three relative scale errors.
The analysis first best fits a sphere onto the MCG points. This identifies a best fitted centre and radius. From this best fitted sphere, the form errors that are the radial deviation from the best fitted spherical surface are analysed in order to identify the CMM geometrical errors. This form error analysis is also a linear best fit of the effect of the CMM errors onto the MCG points. This identifies the three squareness errors of the CMM as well as its three relative scale errors.