Text 1 Sheet-fed Printing Presses

UNIT 8 PRINTING UNITS DESIGN

Vocabulary

screen printing трафаретний друк

squeegee накочувальний валик

guide напрямляюча

frame holder рамотримач

vacuum suction plate форма з вакуумним присмоктувачем

to fasten down закріпити

squeegee guidance напрямляння накочувального валика

squeegee angle кут накочувального валика

pressure force сила притискання

sheet feeding подача аркуша

screen flooding заповнення трафаретної форми фарбою

vacuum printing table вакуумний стіл

drying line сушильна секція

IR drying сушіння інфрачервоним випромінюванням

UV drying сушіння ультрафіолетом

rotary screen printing machine ротаційна машина трафаретного друку

flat screen плоский трафарет

sheet-guiding cylinder аркушенапрямний циліндр

flat-to-round плоскоконцентричний растр

stream feeder самонаклад з каскадною подачею аркушів

to align вирівнювати

stationary printing cylinder нерухомий друкуючий циліндр

gripper затискач, захоплювач аркушів

vacuum pressure вакуумний тиск

suspension rail висяча направляюча шина

cylinder gap паз циліндра

to weld зварювати

unwinder розмотувальний пристрій

hot-air dryer сушарка з обдувом гарячим повітрям

fan-fold delivery вивідний пристрій з фальцюванням гармошкою (віялом)

seamless rotary screen printing ротаційний безстиковий друк

stencil трафарет

thermal writing head термальна записуюча головка

fiber волокно

to image наносити зображення

resolution роздільна здатність

The vast majority of all sheet-fed printing presses use the offset printing technology. Printing press manufacturers supply these presses principally for sheet sizes between 37 cm x 52 cm and 72 cm x 104 cm. The maximum sizes are 120 x 162 cm.

Production speeds lie in the range of 10000 to 18000 sheets/hour, depending on the format, the substrate properties, and the sheet feeder in use. Single-sheet feeders can produce up to 10000 sheets/hour on small-format presses,whereas stream feeders can produce up to 18000 sheets/hour in medium-size format (72 cm x 104 cm).

Various cylinder configurations are possible in multicolor printing presses. The three-cylinder configuration unites the plate cylinder, blanket cylinder, and impression cylinder in one printing unit. The number of printing units arranged in a series, also referred to as unit configuration, determines the maximum number of colors that can be printed in one machine pass.

The middle drum is double-sized, and has two gripper systems; together with a special reversing drum it can be used for sheet reversal. Because of the requirements of the direction of rotation, one or three drums must be located between the impression cylinders for sheet transfer.

Double-sized impression cylinders and transfer drums are advantageous in the printing of cardboard and metal sheeting, since the materials will be subject to less deformation by the cylinders. Presses specially optimized for cardboard printing have double sized impression cylinders and even have triple-sized transfer drums.

Each printing unit has one plate and one blanket cylinder for each two colors and a joint impression cylinder. The two colors are transferred onto the printing sheet in register one immediately after the other, the sheet being held on the impression cylinder by grippers.The sheets are transferred from the first to the second printing unit in this press by gripper systems attached to circulating chains. The chains provide the means to overcome a relatively large conveying distance so that the distance between the printing units is sufficient for a convenient operation. The chain system makes an alignment of gripper systems using special alignment elements on the impression cylinder necessary in order to achieve the required accuracy of transfer for the color-to-color register.

Sheet-fed gravure presses have been developed for packaging printing with two to seven printing units.With this press, the sheets are fed via a feed drum to the first impression cylinder, ink is applied there by the bottom gravure cylinder, which is inked up by means of an inking roller and a doctor blade. There are conveyance chains with grippers installed between the printing units; they take over the printed sheets from the impression cylinder grippers, guide them through the dryers and pass them on to the grippers of the next impression cylinder. At the end of the drying cycle the conveyor chain system behind the last print unit transports the sheets to the delivery unit.

The multicolor sheets printed in sheet-fed printing presses are mostly processed into books, stationery, or packaging media off-line on special machines or flowlines (system of finishing units). In-line finishing operations are, for example:

• sheet reversal for perfecting

• coating the sheets for the most part in special coating units and extended delivery for the drying

• use of rotating cutting blades in delivery to split large sheets and adapt them in this way to smaller-format folding machines,

• configuration of special numbering boxes with a separate inking unit on the impression cylinder of the final printing unit; this enables consecutive sequences of numbers to be imprinted (e.g., for entrance tickets or lottery tickets).

Дата добавления: 2014-12-23