Patent ID: 7939779
Filing Date: 2011-05-10
Classification: B23K

Abstract:
1. A method for laser machining a coated sheet, comprising: placing a coated sheet having first and second surfaces near a laser such that one surface of the sheet faces the laser and the other surface of the sheet faces away from the laser; and generating on the surface of the coated sheet which faces away from said laser at least one topographical change protruding from the surface by directing the laser beam onto the sheet and guiding the laser beam to describe an inward narrowing spiral, whereby the laser beam generates the at least one topographical change protruding from the surface of the sheet which faces away from said beam, by melting through this sheet, and wherein the topographical change protrudes from the surface a height sufficient to provide a spacing gap between the coated surface on which the topographical change was formed and a sheet to which the coated sheet is to be welded sufficient to permit vaporization products formed in the welding process to escape through the at least one gap.