a method of processing a material by use of high kinetic energy comprises a piston driven from a start position by a hydraulic system pressure by a drive chamber , by only one stroke , to transfer high kinetic energy to a blank / tool to be processed , whereafter there is a risk that a rebound of the piston will occur , so a step is taken in connection with said stroke performed , to prevent said piston from making a rebound with an essential content of kinetic energy to avoid negative effects as a result , whereafter the piston is returned to said start position by means of a second chamber , wherein a valve means closes the driving connection between the system pressure and the piston , the valve means is controlled by a pilot valve controlling the entire striking progress , and the second chamber is pressurized with the system pressure during the entire striking progress .