A cold rolling process for impressing a pattern on a surface of a sheet metal article involves passing the sheet article through a pair of rolls and engaging a patterning feature with isolated areas of a surface of the sheet article, at a localized pressure to plastically deform at least the surface of the sheet article. The structure is adapted to easily form an inflation passage between a pillar trim and pillar by using a head liner; therefore, the overall portions of the curtain airbag can smoothly expand during the deployment. The predetermined process is conducted by using a hardware resource when receiving the setting parameter indicating the function option set by the user from the plurality of the function options that the apparatus displays by executing said screen generating program, from the apparatus. The actuation of the servo system is detected and the determined air mass flow is corrected with or directly after a detected actuation of the servo system.