The trouble is, fingerprinting rarely works as expected, and may be costing printers a great deal of money with little in return. Here are a few reasons why:
- Fingerprint runs are expensive. A fingerprint has little meaning unless the press is set to even densities, is warmed up, settled down, and running at actual production speed. And printed on fresh sheets of paper, not the backsides of makeready sheets. That means using thousands of sheets of paper, plus ink and plate costs. Add in hours of time in prep, setup, running, cleanup and analysis time, and you have a cost of several thousand dollars for every fingerprint. Factor that by multiple presses and runs done several times each year and you have a very substantial investment of time and money in a process of dubious value.
- It’s only a snapshot in time. New technologies are constantly emerging, but current offset presses are subject to substantial variability, not only run-to-run, but even within a single run. Even well calibrated and properly running offset press may have TVI variation of +/- 4% within a single fingerprint run. A sheet picked from the low side of this tolerance envelope will be completely unrepresentative of sheets from the high side, and getting sheets that truly represent “normal” behavior can be a challenge.
- The Observer Effect influences results. A frequently-cited 1920′s study by General Electric revealed the so-called Hawthorne Effect: Workers unconsciously act differently when they know they are being watched. In the case of a characterization run, it often means that the press operators are not using the same procedures during a fingerprint run that they use on everyday production work. The result is characterization data that doesn’t accurately reflect real-world conditions.
- They don’t stick. If you conduct a fingerprint run twice a year (and how many really do?) your average data is 90 days old, and things change quickly over time. Summer shifts to winter, rollers wear in, blankets wear down or are changed, new consumable suppliers are brought in, or current suppliers bring in new batches of chemistry or ink. The plate curves that worked so well on the day of the fingerprint run may be hopelessly out of date even a few weeks later. The chances they will still be relevant to conditions five or six months down the line are vanishingly small.
- Emotional investment leads to fear of change. The cost of conducting a proper fingerprint run involves a substantial psychological investment in the process. The result is often a rigidity of approach and reluctance to change even when it is clear that the current plate/press/proof relationship is broken. This fear is often expressed in terms of legacy jobs, as in “We can’t change the plate curves now, we have a rerun of last June’s job coming up in a few weeks and we’ll never be able to match it if we change the plate curves now!”
So, if fingerprint runs are expensive and ineffective, what is the alternative to flying blind if we want to truly print to standards every day? How can the artificial division between fingerprint press runs and real production run be eliminated?
- Integration. The measurement data needed for monitoring press performance and color accuracy needs be integrated into the production schedule, rather than existing outside of it.
- Continuity. The data that is needed in order to regulate the system needs to be collected, not once or twice a year, but on every single press run. Seeing real data every day makes it easy to spot trends before they become problems. A small corrective action can be taken before the shift has become visible, eliminating the problem of matching previous runs.
- Communication. The information required for effective teamwork needs to be shared in real time. A twice-yearly or month-end quality meeting does very little to advance the process. The information visible to the press operator needs to be visible to prepress and other team members at the same time, so they can collaborate for success.
- Actionable Information.Raw data about delta E’s or pass/fail scores won’t get the job done. Both press operators and prepress operators need more. They need to have practical information that gives them specific guidance on what specific actions they can take to improve results.
Even a few years ago, continuous tracking of press performance simply wasn’t practical; but today we have the ability to monitor every press run and share information between the press department and prep department, as well as other interested players in the ink and QC areas.. We can skip the dedicated fingerprint run because now every run can (and should) be a fingerprint run.