Platesetter
Encyclopedia
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.
Plates are often hole punch
ed by the platesetter. External drum units typically punch a plate then load it onto the drum, using the punches to ensure registration on the drum. Internal drum machines will load the plate, punch and image the plate, then release the punches, also to ensure registration. Capstan devices lack the punching mechanism so are considered less accurate in positioning the image on the plate. Capstan devices are most often used for 1 or 2 color printing where their positional inaccuracies are less important.
The imaging of substrate on the platesetter is accomplished by laser. Of the many types of lasers employed in this process they come into two categories. Thermal Laser - the thermal laser images the plate by the heat generated by the laser on the plate. Visible Light Laser - the visible laser images the plate photographically by exposing the plate with light generated by the laser. Of these two types, thermal is the better and more widely used type of imaging for modern platesetters.
Raster image processor
A raster image processor is a component used in a printing system which produces a raster image also known as a bitmap. The bitmap is then sent to a printing device for output. The input may be a page description in a high-level page description language such as PostScript, Portable Document...
and in turn, creates a lithographic
Lithography
Lithography is a method for printing using a stone or a metal plate with a completely smooth surface...
plate suitable for use on an offset press.
For the most part, there are three types of Computer to plate
Computer to plate
Computer to plate is an imaging technology used in modern printing processes. In this technology, an image created in a Desktop Publishing application is output directly to a printing plate....
: Capstan
Capstan
Capstan may refer to:*Capstan , a rotating machine used to control or apply force to another element*Capstan , rotating spindles used to move recording tape through the mechanism of a tape recorder...
, 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.
Plates are often hole punch
Hole punch
A hole punch is a common office tool that is used to create holes in sheets of paper, often for the purpose of collecting the sheets in a binder or folder.The origins of the hole punch date back to Germany via Matthias Theel, where two early patents for a...
ed by the platesetter. External drum units typically punch a plate then load it onto the drum, using the punches to ensure registration on the drum. Internal drum machines will load the plate, punch and image the plate, then release the punches, also to ensure registration. Capstan devices lack the punching mechanism so are considered less accurate in positioning the image on the plate. Capstan devices are most often used for 1 or 2 color printing where their positional inaccuracies are less important.
The imaging of substrate on the platesetter is accomplished by laser. Of the many types of lasers employed in this process they come into two categories. Thermal Laser - the thermal laser images the plate by the heat generated by the laser on the plate. Visible Light Laser - the visible laser images the plate photographically by exposing the plate with light generated by the laser. Of these two types, thermal is the better and more widely used type of imaging for modern platesetters.
External links
- Computer to Plate Forum - Online Community of End Users, Dealers, and Repair People using Platesetters, Q & A Forum