Method for controlling an ultrasonic machining process

Method for controlling an ultrasonic machining process, in which an ultrasonic vibration of the frequency f is transmitted with the aid of a sonotrode made to carry out an ultrasonic vibration under a pressure into the material to be machined, wherein, during a first machining interval, a first welding variable of the group S, consisting of the frequency f of the ultrasonic vibration, the amplitude ü of the ultrasonic vibration of the sonotrode, the force F, which the sonotrode exerts on the material to be machined, the power P, which the generator delivers, and the speed v, with which the sonotrode is moved in the direction of the material to be machined, is kept constant until a first target variable of the group Z, consisting of the force F, the power P, the welding time t since the beginning of this machining interval, during which the excited sonotrode transmits the ultrasonic vibration under pressure into the material to be machined, the welding path s, which the sonotrode has covered since the beginning of the machining interval, and the energy E, calculated from the product of P and t, adopts a predetermined value, and, during a second machining interval, which adjoins the first machining interval, a second welding variable of the group S is kept constant until a second target variable of the group Z adopts a predetermined value, wherein the first and the second target variable differ, wherein said first target variable and a fourth target variable of the group Z are detected during the first machining interval, and wherein the first machining interval ends when the first target variable adopts the predetermined value or wherein the first machining interval ends also when the fourth target variable of the group Z adopts a predetermined value, whichever occurs first.