Evaluating the results

1. Evaluate the average measured arm radius, RAV as follows:

MCG RAV formula

2. Evaluate each measured arm radius for its deviation from the average measured radius as follows:

MCG formula

3. Evaluate the range of deviation for each run, known as the ‘span'.

4. Evaluate the range deviations over all three runs, i.e. the maximum deviation in the + and - directions.  This is the VOLUMETRIC MEASURING PERFORMANCE (VMP) for the volume swept by the arm radius R as follows:

MCG VMP formula

5. Evaluate the range of deviations for each measuring position.  This is the SYSTEM REPEATABILITY at that POSITION.  A suggested layout is shown overleaf.

6. When the MCG indicates an unacceptable performance of your CMM, contact the OEM to service the machine (please note that this service cannot normally be undertaken by the user).

MCG repeatability