position of the piston 5 from the workpiece if the piston has been moved over the aforementioned distance the stamping tool strikes the workpiece to be shaped this occurs in the position of the piston denoted in fig4 by pos 1 then the adjustment means 60 increase the pressure of the high pressure supply 24 to a value p 2 which is markedly higher than p 1 and typically corresponds to the maximum pressure of the high pressure supply 24 this high pressure is maintained for the further movement of the piston 5 in the working direction 11 for a sufficiently long time until the stamping tool attached to the piston rod 6 has penetrated the workpiece position pos 2 of the piston 5 in fig4 thus the working load on the piston 5 is reduced if a further movement of the piston 5 in the working direction 11 is provided as far as the position pos 3 the adjustment means 60 reduce the pressure of the high pressure supply 24 to a value p 3 which is less than the pressure p 2 and in particular is the same as the pressure of the low pressure supply 26 during the return movement of the piston 5 counter to the working direction 11 the control slide valve 30 blocks a further throughflow of hydraulic fluid from the high pressure supply 24 into the working pressure chamber 13 a volumetric flow of hydraulic fluid from the high pressure supply 24 consuming a high level of energy is thus prevented the return movement is only effected by a volumetric flow of hydraulic fluid from the low pressure supply 26 the disclosed exemplary embodiment of the invention considerably reduces the energy requirement in typical use with repeated extending and retracting of the piston.