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Direct Imaging Presses

Direct imaging technology provides for the direct transfer of the image from digital files to the image carrier (plate) of the press. A direct imaging press is basically a conventional offset press except that the image carrier (plate) is imaged directly on the press with built-in laser exposure units. Many of the press settings, such as plate registration, ink flow, and cleanup are adjusted with digital information as well. Unlike a true digital press, which can vary the image on every printed sheet, the image cannot be varied during a press run on a direct imaging press.

The advantage that direct imaging presses have over offset presses (without direct imaging capabilities) is that the preparation time per job is greatly decreased. Many of the manual steps of conventional prepress and presswork are eliminated, such as producing films, preparing the films for platemaking, creating plates, and mounting and registering plates on the press. The print quality is excellent with direct imaging presses because the print process is still based on offset technology.

Although direct imaging presses cannot accomplish variable information printing like true digital presses, some DI presses are able to print different versions of a document during a single press run. For example, a five-color press can use four print units for printing the full color static portions of a document and use the fifth unit to print the different versions of text that are needed. The plate on the fifth print unit is reimaged at the appropriate intervals for each version that is required. After the plate is imaged, the printing proceeds until it is time for the next plate to be imaged, and so on. The result is a document that has the same layout and color elements, but differences in the text for each version. This is a much better process compared to conventional printing in which a separate base run is printed and then the sheets are run back through the press at a later time to print the different versions of text (sheet-fed press), or when using a roll-fed press, having to print the static portions along with the text for every version.

The majority of direct imaging presses are capable of a minimum resolution of 1270 dpi which is suitable for producing nearly 90% of all print jobs. Many DI presses offering much higher resolutions than 1270 dpi so there are few applications that are not suited for DI presses.

DI presses are very profitable in the 500 to 10,000 impression market. They have a lower cost per page in that quantity bracket than most other technologies that are comparable, such as CTP (Computer To Plate) and conventional offset printing. Direct imaging presses are a good choice for those who want the quality of offset printing with the advantages of a digital workflow.

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