What are the types of output devices used in pre-press?

Answer 1

The most popular output device has two names: the CTP device and the Platesetter. CTP means Computer to Plate. It's a machine that exposes printing plates from data sent to it by a digital front end. These are huge. There's also a special paper you can get for a tabloid-size laser printer that lets you make plates on the laserwriter. There have been paper plates for decades--the quick-print industry revolves around their existence--and the laser printer ones aren't any worse than the traditional Itek plates. I've always run imagesetters, which expose film from data sent to it by a digital front end--usually the SAME DFE you'd use with a platesetter. A few companies make Direct Imaging presses. Heidelberg is the leader in this arena. In those, the plate exposing units are mounted on the press and the DFE is connected to them...very slick technology for short runs. Heidelberg has sold a lot of these to quick-print shops. I forgot one, mainly because the rotogravure process isn't all that common anymore. Rotogravure is good for two things: insanely long publication runs--the average gravure run is probably two million impressions--and huge label orders, especially ones that need a lot of color laid down. It has four advantages: very high speed--gravure presses run well in excess of 3000 feet per minute; very wide webs--three-meter webs are fairly common on gravure presses, which allows you to do things like run a 64-page magazine sig on one press sheet; total freedom from color change caused by wearing out the plates; and the ability to just pack a sheet with color. Gravure uses solvent-based ink. The print from unit one is completely dry before the job reaches unit two, so all the "total ink coverage" calculations we do in offset to make sure you're not going to plug up the sheet just go out the window--if you want to run 95-percent screens on every unit on your press, be my guest. Gravure prints using a copper-covered cylinder. They polish it to a mirror finish, then engrave little pits into its surface. The cylinder is coated with ink, which is then scraped off the surface. The pits retain the ink, which is then transferred to the sheet. Cylinders are engraved in a cylinder-engraving machine called a Helioklischograph. Heidelberg makes them--maybe one a year. Heidelberg has always made them. Heidelberg hasn't ever made gravure presses. Go figure.