There are various kinds of printing presses, each with advantages for planning specific printing jobs.
Sheet fed: Individual sheets of paper are fed into the printing press. Usually higher quality, slower speed and more expensive than web presses. Publication has to be trimmed and bound.
Web Fed: Paper is fed into the press from a large roll. Offers speed at the expense of quality, although some web presses can print higher quality color. Long -un print jobs which require speed, such as newspapers, are almost always web fed. Generally, paper rolls are of newsprint or offset stock, but some higher quality web presses can utilize coated stock.
Flat Bed: Printing surface is flat. Offers higher quality, but slower speed, and, possibly, increased cost. Can be sheet fed or web fed. Because most printing today is done by the offset process and nearly all offset presses are rotary, there are fewer flat bed presses except for specialized printing. Screen presses are frequently flat bed, for example.
Rotary: Printing surface is curved. Offers the highest speed printing. Most offset presses are rotary, so most printing today is by rotary presses.
Perfecting: Prints on both sides of the paper at the same time.
Combinations: These five variables can be mix and matched in any combination: sheet fed, flat bed perfecting or non-perfecting; web fed rotary perfecting or non perfecting, etc.
Advantages: Web presses offer speed over quality and can significantly reduce costs, especially with folders and pasters attached to the end of the press. Sheet fed presses offer the highest quality, but at slower speed and increased cost. There are specialized, higher quality web fed presses which can offer high quality color on coated stock at significant savings, but these are only practical for longer run print jobs (10,000 plus).
Press Units: Each unit of a press prints one signature, or one side, in one color. A multi-unit press can run numerous signatures, or multiple colors. For example, a seven-unit press can print one 16-page 8-1/2x11” signature in Hexachrome with varnishing for the pictures. If a standard wide unit press can print 8 tabloid newspaper pages per unit, then four units can print eight pages in four-color or 32 pages in one color (black).
This photo is of a four unit, web-fed, rotary press, capable of printing one signature of process color.
Department of Communication, Seton Hall University