Imbalances in rotating grinding tools can be static or dynamic and are caused by excentricity, form errors, or structure errors (Fig. 5.3). Imbalance, U, is defined as the product of the mass, m, that is out of symmetry and the excentricity, e, towards the rotational axis (Eq. 5.7) [KLOC09, p. 284, DIN05]. Standards, such as DIN EN ISO 6103 define the tolerable imbalance for conventional grinding wheels depending on their application [DIN05]. Large masses can lead to spindle bearing damages [MPM12].
Imbalance U = m • e (5-7)
The form induced imbalances such as excentricity or tool shape errors can be eliminated by the conditioning process [KLOC09, p. 282]. Non-dressable tools such as electroplated, superabrasive grinding wheels are manufactured with a high precision, so that the abrasive layer generally is aligned to the core hole to 1 qm cylinder running [KLOC09, p. 282 f.]. Imbalances due to structural inhomogeneities or form induced errors are minimized by additional tool balancing [KLOC09, p. 283].
Most balancing systems work as static systems, i. e. in only one plane. Dynamic balancing happens in two planes and is mostly important for wide grinding wheels such as centerless grinding wheels [KLOC09, p. 283, WECK05, p. 245]. Imbalances result in vibrations, which are commonly detected by piezo sensors and oscillators.