Parametric Excitation of Vibrations in Printing Machines

In this paper the parametric excitation of vibrations in printing machines is analysed both experimentally and theoretically. Initially, selected results from experimental studies of these drive-belt-induced torsional vibrations are discussed. For this, twelve different drive belts are used during experiments at a test rig and at a sheet-fed offset printing machine. Measured vibration amplitudes from machine and test rig correlate very well. Depending on the chosen drive belt, large vibration amplitudes occur during printing in the vicinity of a critical production speed, where the first drive belt order coincides with the machine’s first eigenfrequency. This results in a clearly visible rhythm during printing and is therefore unacceptable. It is demonstrated experimentally, that active vibration control can be used successfully to reduce these parametrically excited torsional vibrations in sheet-fed offset printing machines. Furthermore, the machine is modelled as a dynamical multi-degree of freedom system with time-periodic coefficients, and the parametric excitation of torsional vibrations is studied numerically. First, a numerical stability analysis is carried out employing Floquet theory. The system’s damping parameters are derived from measured machine data. Accordingly, a simulation model with drive control results in parametrically excited torsional vibration amplitudes that match very well with measured amplitudes.