Ink Presetting

Sustainability and waste reduction go hand-in-hand, and getting to the correct colors quickly can minimize package-printing waste during makeready.

Package printers are faced with rising material and energy costs, as well as global competitive pressures. Makeready waste can put an additional squeeze on profits. Printing in many market segments, including niche markets, demands shorter run lengths, which increases makereadies and compounds the problem. Automatic registration systems now enable most printers to be in register very quickly after press start-up. Waste, however, continues to pile up until color, which is essential to brand success, is set.

If the materials, like paper, paperboard, and foil, and the ink and press time wasted during makeready can be reduced, these savings will flow directly to the bottom line. Waste reduction would also have a positive impact on a printer's efforts to be environmentally-responsible. Ink presetting as an economical solution to set color quickly and reduce waste is a trend that continues to gain momentum.

The basic premise of presetting is that there is a predictable relationship between the percentage of dot coverage on the plate and the ink key setting required to supply the correct volume of ink. The first step is to determine the coverage on the plate. Today, most printers compose digital image files for use by image setters or CTP systems. Presetting systems can use software running on standard PCs to analyze the image file for the film or plate and determine the percent coverage in each key zone. Some systems require CIP3/4 files as input, while others can accept a variety of image file formats. In most cases a low density file is desired to keep the total processing time reasonable.

A second software application is needed to convert the percent coverage in an ink zone to the correct key setting. There is a direct (but not linear) relationship between coverage and correct key setting. Presetting software uses this relationship together with the zone coverage data to calculate the required setting for each key on each fountain. Because fountains are not identical, most systems provide a means to account for these differences in the calculations. Some systems also provide a means of adjusting the key settings based on the characteristics of the material being run.

Finally, the calculated key settings must be transferred to the ink desk controlling the keys on the press. Settings can be conveyed to the ink desk by a direct connection or by a variety of media. The ink desk's computer will then accurately set the keys as required. However, the settings conveyed to the ink desk must be routed to the proper fountains. For a sheetfed press, color alone can identify the proper fountain. In web press applications, the specific web, side, and color must be identified for correct routing. Some systems can also use page number and color for routing.

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