Letterpress machine

As letterpress printing machines is known printing machines , which according to the high-pressure process (eg. B. movable type) operate. The term letterpress press is also used .

The letterpress printing process is the letterpress printing process significantly improved by Johannes Gutenberg in the 15th century. In the period from the 16th to the 18th centuries, printing technology had not undergone any changes. Over time, more and more wooden parts were replaced by metal. This process was and is mainly used to print books, but magazines and commercial jobs are also printed using letterpress. Since books can be printed using other printing processes , it is important to note that letterpress and book printing are not the same processes. Book printing is also called work printing .

The sheet-fed and reel-fed printing presses are no longer built today, but are still in operation in some printing plants. Originally, the printing process was purely manual until it was gradually mechanized.

construction

The machines consist of a printing form carrier in flat or cylindrical form, an inking unit and a counter pressure body. The counter pressure body is either a crucible or a cylinder. The printing form can be assembled from individual parts or manufactured in one piece. It is colored with the help of the inking unit. The sheet or paper web is guided between the printing forme and the counterpressure body. An elastic elevator of paper or board sheet prevents damage to the printing material and the printing form. This may have to be prepared .

Printing principle

There are separate letterpress machines for each of the three printing processes .

The flat on flat principle is the oldest method used. Here, the downward movement of the printing platen creates a pressure on the paper and the inked printing plate. The printing table is not moved during this process.

In the 19th century, the principle of round on flat for letterpress printing developed from the copperplate press of gravure printing. Friedrich König transferred the principle to his high-speed press, the stop cylinder press . In machines that work according to this principle, the contact pressure is generated by rotating the cylinder on the printing form. The printing movement takes place via the printing cylinder. This in turn rolls off on racks attached to the mold bed. Accordingly, the printing cylinder is in motion while the forme bed is stationary.

With machines based on the principle of round on round, the printing process takes place via two synchronously running cylinders. The round printing form is attached to the form cylinder. The paper is pressed onto the forme cylinder via the impression cylinder either as a sheet or a roll and printed.

Printing block / printing form

The cliché is a name for a printing plate in letterpress printing. This cliché is brought to a font height of 62 2/3 points by applying it to a base or by back-casting with lead.

In modern letterpress printing, in addition to hand typesetting , machine typesetting , autotypes and line etchings are also used for printing form production. The printing form consists of medium-hard material such as B. lead, wood or fiber-reinforced plastic as well as clichés (zinc, magnesium, plastic, linoleum). In flat-forming machines, both sets of individual types and of line sets, stereos and clichés as well as mixed sets of the types mentioned are used. Because of their horizontal foundation, flat-form machines are suitable for printing almost all types of record. For crucible machines, only well-closed individual type sets as well as cliché sets and stereos are used. Mixed rate is possible, but is reluctant to print because of the risk of loosening. Rotary machines usually only work with stereos or curved clichés. In flexographic printing machines, these are called sleeves.

Machine types

There are different machines depending on the printing principle.

There are three different types of drive for each machine. The machine is operated as a hand press, semi-automatic or automatic press, depending on the situation. With the hand press, the entire printing process is carried out manually. The press is operated with a hand crank. The coloring is done using a printer pad . Semi-automatic presses are all presses that are partly operated with a hand crank and partly with an electric motor. The inking works either via a hand roller or via an electrically operated inking unit with an inking roller and inking application rollers. Examples of semi-automatic presses are the set pressure press and the platen press.

Heidelberg crucible

In contrast to this, the entire printing process is done automatically in the fully automatic press. Machines that work fully automatically are, for example, the Heidelberg cylinder or Heidelberger crucible and stop cylinder machines . Hand crucible and automatically nachfärbende Abziehpressen are therefore the simplest forms of printing machines, Rotary quickly press and printing machine the komplexesten.

Inking unit

Letterpress machines are typically single-color machines. The plate printing presses have both plate inking units and cylinder inking units . Table inking units and cylinder inking units are used in flat-form presses. Only cylinder inking units are common on rotary presses.

features

A characteristic of letterpress printing is the formation of squashed edges due to the slight settling of the inking rollers on the raised printing forme elements. These can be seen on the sharply delimited edge with a significantly sharper color. In addition, shading can be seen on the back. This is characterized by weak embossing of the printing form elements.

literature

Gerhardt, Claus W .: History of the printing process . Part II. The printing. Stuttgart: Anton Hiersemann Verlag, 1975. ISBN 3-7772-7521-2
Giesecke, Michael: Book printing in the early modern times . 4th edition. Frankfurt am Main: Suhrkamp Verlag, 2006. ISBN 3-518-58456-1
Hiller, Helmut and Füssel, Stephan: Dictionary of the book . 6th edition. Frankfurt am Main: Vittorio Klostermann Verlag, 2002. ISBN 3-465-03220-9
Laufer, Bernhard: Basic knowledge of typesetting printing paper . Düsseldorf: Verlag Buchhandler heute, 1984. ISBN 3-920514-19-X
Liebau, Dieter and Weschke, Hugo: Polygraph specialist lexicon of the printing industry and communication technology . Frankfurt am Main: Polygraph Verlag, 1997.
Scheper, Hans Jürgen: Examination knowledge printing technology . Itzehoe: Verlag Beruf und Schule, 2005. ISBN 3-88013-623-8
Wolfsturm, Hans-Jürgen and Burkhardt, Hermann: high pressure . Ravensburg: Ravensburger Buchverlag, 1994. ISBN 3-473-48382-6