Newspaper publishers are facing ever-increasing material, labor and energy costs even as competitive pressures limit the opportunity to recover those costs through price increases.

Add to that the fact that in most market segments, run lengths are decreasing and make-readies per day are increasing.

Bottom line? A serious squeeze on profits.

In response, publishers are examining the deployment of automatic ink presetting systems that can be used to set color quickly, and thus compress the amount of ink and press time wasted during makeready.

Requirements

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. Plate scanners were once the primary means of doing this. However, most printers are now composing digital image files for use by imagesetters or computer-to-plate 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 paper 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. In web press applications, the specific web, side and color must be identified for correct routing. (For a sheetfed press, color alone can identify the proper fountain.) Some systems can also use page number and color for routing.

Keys to success

The objective of the presetting system is to achieve uniform target density across the print as quickly as possible after startup. To accomplish this, other variables that affect proper key setting must be controlled. Ink key zero settings must be properly calibrated in order for the calculated key settings to accurately produce the expected blade opening.

Fountain lockups must consistently close the fountain to the same position each time in order for zero settings to be accurate. Micro rollers, if used, must be set parallel and within manufacturer specifications for gap. Other variables that affect ink key settings at startup, such as ink ball speed, ductor settings and water settings, must be standardized or under control of the presetting software.

The proper non-linear curves or formulas for converting percent coverage to key setting must be determined. To do this, test plates are run and their image files processed to preset the ink keys. Preset key settings are then adjusted to achieve uniform density at target value across the printed sheet for each color. In this process, color bars and quantitative density measurements will produce more accurate results than visual judgment.

Basis for correct conversion

These “OK” settings are the basis for determining the correct conversion curves for the press. Creating curves to match the OK settings is done manually on some systems, automatically by software on others.

Achieving and maintaining optimum preset results requires periodic evaluation of preset performance. In this effort it is desirable to have a quantitative or graphical method of measuring the amount of correction the press operators need to make in order to achieve desired color. This requires capture of preset key settings as well as OK key settings.

Because the objective is to quickly achieve desired color under startup conditions, it is more appropriate to capture OK settings as soon as desired color is achieved rather than at the conclusion of the run. It is useful to collect some printed sheets at the same time to allow later evaluation of the correctness of the OK settings. This information will enable the user to fine-tune the conversion curves and minimize the need for additional adjustment after preset.

Payback

With the shift to more jobs of shorter run length, the impact of makeready waste reduction can be substantial. Reducing the number of current waste impressions by 20 percent to 50 percent is typically achievable. If, for example, a web press runs only one web, six days per week, seven makereadies per day, with 3,000 waste impressions per makeready, it is generating 126,000 waste impressions per week. A 40 percent reduction in waste impressions through presetting will save 50,400 impressions per week. At a cost for paper and ink of .045 cents per impression, the savings are $2,268 per week, or almost $118,000 each year.

 While each web printer’s volume and potential saving is different, clearly there can be a substantial return and rapid payback of the investment. Run your own numbers to see how much presetting could benefit your shop.


Peter Griffin is president of EPG, a company that specializes in the design, manufacture and service of integrated color control systems and software. Griffin can be reached at 860.767.7130, extension 11, or via e-mail at pgriffin@epg-inc.com.