Soft bearing horizontal
In addition to the hard bearing machines, soft bearing balancing machines are still manufactured for some applications. In this case the stiffness of the pedestals is very low and therefore the rotational frequency during balancing is at least three times higher than the resonance frequency of the rotor mounted on the machine pedestals.
Soft bearing machine are used with some advantages for rotors of small dimensions or for high rotational speeds; typical applications are: small electric motors, balancing of fans with their own motor and drive shaft balancing.
In these cases the balancing machine must be calibrated initially by means of trial runs with known unbalances, but this is not a problem for production balancing.