## 3 Experimental Tests
Two base holes are also indicated--the center of hole B is simultaneously the origin of the reference system for both the CMM and the CNC machine. Base hole A is used to properly align the cover--the x-axis of the reference system goes through its center. The distance between axes of the base holes A and B is 700 mm. The distance from the axis of the base hole B to the axis of seat 2 is 587 mm, and the distance from the axis of hole B to the axis of seat 6 is 197 mm. The true position tolerance of hole axes from 1 to 9 is 0.076 mm, and bearing seat diameter tolerance is 0.050 mm. The true position tolerance provides information about the maximum allowable deviation of a feature (e.g., hole, slot) from its true position. By true position, we mean the ideal position of the feature according to design. Upon completion of the operation, the machine accuracy was again verified, according to ISO 230-2:2014 and ISO 230-6:2002 and the test described in [25]. No significant change in the values of geometrical errors of the machine tool was registered. All values were once more within the required tolerances adopted for a new machine, such as geometric accuracy of machines operating under no-load or quasi-static conditions, determination of accuracy, and repeatability of positioning of numerically controlled axes. Then reference measurements of the covers were carried out in the measurement laboratory according to a standard measurement procedure approved in the production technology. These measurements constitute a point of reference for a new developed quality control procedure. For measurement, a Mitutoyo coordinate measuring machine (manufactured by Mitutoyo Corporation, Kawasaki, Japan) with a Revo2 rotary head and Modus 1.7 measuring software (developed by Renishaw plc, Wotton-under-Edge, UK) was used (Figure 6). The accuracy of the CMM was evaluated based on the standard ISO 10360-2:2009. ISO 10360-2:2009 specifies the acceptance tests for verifying the performance of a coordinate measuring machine (CMM) used for measuring linear dimensions as stated by the manufacturer. It also specifies the reverification tests that enable the user to periodically reverify the performance of the CMM. The acceptance and reverification tests given in ISO 10360-2:2009 are applicable to Cartesian CMMs using contacting probing systems of any type operating in the discrete-point probing mode. According to the mentioned standard, the uncertainty of CMM measurement is 5 \(\upmu\)m.  
Figure 5: ADT casing cover model with bearing seats and base holes (yellow) indicated. On the basis of measurement results, hole position deviations (HPDs) for bearing seats with respect to nominal values were determined. Deviations determined on the basis of measurements on the CMM were designated as \(\text{HPD}_{\text{CMMi}}\), whereas deviations determined on the basis of measurements on the CNC machine were designated as \(\text{HPD}_{\text{CNCi}}\), where I = 2, 3,..., 8 indicates the number of a bearing seat. Hole position deviations for base hole 1 were determined in a similar manner. Afterward, the correlation of CMM data with CNC machine data was examined by determining the Pearson correlation coefficient. The values of the correlation coefficient are presented in Table 1. The axis of hole 9 presented in Figure 5 is the origin of a coordinate system for measurements on the CNC machine and on the CMM. For this reason, it was not included in Table 1.  
The obtained values of the Pearson coefficient indicate that the correlations are negligible to moderate in size [26].