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This paper gives an overview of impact printing and reviews some of the more recent advances made in this printing technology. Matrix and fully-formed-character impactprinting technologies are discussed for both serial printers and line printers. The critical electromechanical subassemblies that are described are the hammer unit, the paperhandling system, the inking system, and the type-element system. The mathematics describing printer performance and the operation of some of the subassemblies are presented. The relative simplicity of the impact printer still allows it to be the most economical form of text printing. Its other advantages are reliability, general insensitivity to environment, and the ability to print on the greatest variety of print media.
Introduction
Impact printing, which had been the predominant printing technology for large systems as recently as eight years ago, still plays an important role in satisfying the printing needs of many users. Typically, impact printers are more reliable, lower in cost, more tolerant to a variety of print media (paper types), and less sensitive to environmental conditions than their non-impact counterparts. Additionally, there are unique applications that can be satisfied only by impact printers, such as printing on multipart forms, printing in hostile environments, and higher efficiency for sparse printing. The disadvantages of impact printers are related to their poorer print quality and their lack of flexibility and performance with respect to complex fonts, images, and color. In addition, the acoustic levels for the very low-speed impact printers can be relatively high.
Impact printers can be divided into two different technologies and two different configurations. The two configurations are line printing and serial printing [1]. In the line-printing configuration, all of the characters that comprise a line are printed more or less at the same time; i.e., printing takes place one line at a time. In the serial configuration, printing is performed one character at a time, the characters being printed sequentially. The two impact technologies are fully-formed-character printing and matrix printing. In the former, the entire character is produced by means of a single impact creating a fully formed character. In matrix printing, characters are created as a result of numerous impacts producing dots that form the desired character. Thus, impact printers come in four varieties: fully-formed-character line and serial printers as...