Method for operating a hydraulic press, and hydraulic press

A hydraulic press, comprising:

• a hydraulic cylinder, which has at least one chamber,
• a ram, which is coupled to the cylinder and on which a shaping tool for shaping a workpiece can be coupled;
• a hydraulic pump, which has a pressure fitting,
• a motor, which is coupled to the pump and has a nominal speed nN,
• a hydraulic accumulator, which is connected to at least one of the chambers and the pressure fitting,
• a tank for hydraulic fluid, which is connected to at least one of the chambers,
• an accumulator pressure sensor for registering an accumulator pressure pS prevailing in the accumulator;
• a control unit, which enables an operation of the press in cycles and is connected to the accumulator pressure sensor and the motor;
• wherein:
• the motor is implemented such that its speed can be set to the nominal speed nN and to at least one intermediate value nZ, for which 0<nZ<nN applies;
• the control unit is implemented such that:
• in at least one phase of each cycle, hydraulic fluid is pressed out of the accumulator into at least one of the chambers by the accumulator pressure pS, to move the ram in relation to the cylinder;
• in at least one part of each cycle, the pump conveys hydraulic fluid into the accumulator with a charging volume stream and the control unit regulates the accumulator pressure pS to a pressure reference variable PSOLL, in that it sets the speed of the motor to the nominal speed nN and to at least one of the intermediate values nZ.