Why do we need multi speed balancing machines?

Multi speed balancing machines are normally big size machines and machines which handle a range of jobs. In case the component is a mass produced component with predictable levels of unbalance, single speed machines can be tuned to balance the components faster and well within the tolerance. But in heavy components, the level of unbalance may not be known initially. It may be hazardous from the point of safety to directly run the component at the required balancing speed. So, heavy components are run at lower speeds, initial balancing is done. Further balancing is done at higher speeds till the desired level of accuracy is achieved.