an acceleration pressure is used as set value for the movement of the mass which is to be shifted , such as the mold clamping unit in an injection molding machine . for this purpose it is proposed to use preferably an electrically modulated pressure control valve for the pressure regulating device in the pressure drive system . even with extremely short acceleration periods resonance oscillations are avoided , which until now prohibited the reduction of the acceleration period . with computing devices the movement of the mass can now be really controlled in relation to a selected velocity profile and / or a position profile or at least a part thereof .