PRINTING 240,000 PAGES PER HOUR
The cylinders turn at the rate of 300 revolutions per minute which means that the paper runs through the machine at nearly 14 miles per hour. Summing up all the webs we have a total consumption of 108 miles of paper per hour. The paper is 6 feet wide and the weight of paper in an hour’s run is about 18 tons and the hourly production is 150,000 sixteen-page papers. When color is used, the press will deliver 50,000 24-page papers per hour with the two outside pages printed in three colors and black. The course of the color printed web must necessarily be different from that of the plain black printed web. It must pass through a number of printings; and to prevent the moist ink from transferring to the impression rolls and from them back to a succeeding page, thus soiling or blurring the impression, an extra roll of thin paper is passed between the printed web and the impression cylinders. This acts in a measure as a blotter. The offset paper is taken up on a roll and used over and over again. It is used not only for color work, but also when fine half tone engravings are to be printed so that a cleaner impression may be obtained.
The inking system of printing press is very elaborate. It is highly essential that the ink be spread upon the type surface in just sufficient quantity to be picked up by the paper and that the ink be uniformly distributed over the whole surface. There is an ink reservoir and a set of inking rollers for each cylinder. The reservoir consists of a trough running the whole length of the cylinder. At each turn a revolving roller dips into the ink and transfers a thin film of ink to a series of small rollers. These are grouped about a large roller to which they deliver the ink. The small rollers have an axial reciprocating motion whereby the ink is uniformly spread over the large roller. The latter transfers its thin coating of ink to a pair of rollers known as “form rollers” and these in turn deliver the ink to the printing cylinder.