Modal Assurance Criterion as an iron cast and hybrid machine tool's body comparison tool

The paper presents the results of research on increasing the dynamic properties of the machine tool body. For this purpose, a hybrid body was manufactured, which was created by filling the free technological spaces in the cast iron body with a polymer concrete material. The modes of free vibrations, modal frequencies, amplitudes, and damping ratios were revealed using experimental modal analysis. In some cases, the amplitude value decreased by up to 68%, as well as the damping ratio increased by almost 109%. Then, using the MAC (Modal Assurance Criterion) method, the body with polymer concrete fillings was compared with the cast iron body to estimate the degree of similarity of the various modes of free vibrations of both structures. The obtained results in the range of 0.54–0.96 indicate high similarity between the vibration modes, which were revealed in both analyses.