Platesetter

A platesetter is a machine which receives a raster image from a raster image processor and in turn, creates a lithographic plate suitable for use on an offset press.

For the most part, there are three types of Computer to plate: Capstan, External Drum and Internal Drum. Capstan type platesetters feed a roll of plate material through the imaging area at a set, continuous speed. After exposure, the material is cut and the plate is ready for the press. Capstan devices are generally considered the most affordable, but least accurate method of producing plates. External drum platesetters work by having the plate affixed to the outside of a rotating drum. As the drum rotates, the imaging unit moves parallel along the length of the drum, imaging as it moves. An Internal drum platesetter works by having a plate set inside of the drum. The imaging unit, or a spinning mirror, traverses the center of the drum, imaging as it moves.