The present invention relates to the production of a series of holes in a layer of material, in particular to the production of a target rupture line in a first layer of an airbag cover. The radiation of a plasma that forms during the production of each hole is detected from the surface that is being machined. From the signal pattern derived, the time of the beginning of the signal and the time of the appearance of a falling edge that meets a predetermined edge criterion are detected and stored. The point in time at which the falling edge appears is a switching criterion for switching off the laser. The difference between the two points in time stored for each hole constitutes a quality criterion for the respective hole.