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Gravure was actually the first printing process to use computer-to-plate technology. Electromechanical engraving techniques, which reproduce the digital image onto the gravure cylinder, have been in use for a number of years. Digital engraving can produce much finer detail than conventional methods. Clear and distinct typefaces can be achieved that do not break up before other areas of the image, which can occur with conventional engraving methods.
Direct digital electromechanical engraving is the process used to produce most of the plates for the gravure computer-to-plate process. With this process, photographic prints are mounted on a rotating drum where they are scanned. The scanner records the different densities of the image as analog signals, which are then converted into electrical impulses (digital record). The scanner is linked to a diamond stylus, which uses the electrical impulses as a guide to engrave up to 6000 individual depressions per second into the copper gravure cylinder.
Gravure cylinders can also be engraved with lasers. Copper reflects laser beams so there is a special metal alloy that is used to prevent this problem. Like copper, the metal alloy can be plated onto a steel cylinder. The laser engraver can etch as many as 70,000 depressions or cells per second into the metal alloy using the digital record. |