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FLEXO Magazine : November 2012
are various opinions in the industry on how to achieve desired outcome, all can agree that Flexographic Image Reproduc- tion Specifications and Tolerances (FIRST) guidelines provide the basic understanding for control and repeatability in the flexographic process. Think of FIRST as the “Five S’s of Printing. ” You sort, set in order, shine, standardize and sustain. This journey begins at press by doing an optimization of your press operation, thereby assuring yourself there are no mechanical issues that will hin- der the print process. Gears, bearings, frame walls and drying function are some of the many sources of mechanical prob- lems. Press cleanliness is also very important to maintain. We often find tinkering related to fatigued equipment. Equipment must work as designed, or it will cause problems for you when it counts. Smart tool selection is part of it. When we talk about the right tools, we often think of the basics. Also, consider tools for the operator that help maintain the process, like tools for measurement and inspection. Once a press can hold proper register, avoid adding to physical print changes, like bounce or chatter, and adequately dry the ink, you are well on your way to having an optimized print process. We often find optimization steps skipped, only to rear up during the print process. Once an optimization has been completed, you define the print process and capabilities by doing a fingerprint. Fingerprinting is the step where numeri- cal values are defined and which will allow for measurements and repeatability. All conditions need to be documented, like tension, tools used—tape, plate, ink type, anilox, etc. Many of the inputs we will discuss later on. Once the press capability is harnessed, a characterization run will allow the prepress team and customer to realize the full potential and limitations of a particular press and the combi- nation of variables, based off of repeatability. Lastly, and most importantly, these three steps of Optimization, Fingerprint and Characterization, will undoubtedly improve communication among all parties and build a foundation of understanding for further process improvement. Please remember, maintain the press if you expect to sustain repeatability. Press inputs are defined as the parts that come to the press, so a print job can be assembled and printed. Again, the five inputs are prepress, ink, anilox, plate/mount and print samples. Furthering the investigation of these sources, two classifications were developed: 1. Internal—what the operator can do at press 2. External—what must be done before going press PREPRESS FUNCTIONS Let’s look at prepress from the viewpoint of the operator. What are the realities? Internally, the operator can only main- tain proper press conditions. Thinking about it, any changes in printing process to satisfy one area would yield undesired consequences to other areas. A normal, repeatable setup, which the operator can supply will serve to isolate a prepress issue, but not address it. In these cases, the problem must always go back upstream. Externally, there are a few common sources you will want to examine to see if they are addressed in the operation. Cer- tainly, an operation would want to be based on a fingerprint/ characterization where standards have been established for both press and prepress. Print efforts that avoid this basic tenet of process control and capability will be fraught with problems. To achieve consistency and avoid guesswork for the opera- tor, targets must be in the artwork, or the operator will not be able to control the process. If an operator is asked to qualify and run a job without control targets to help them measure, then you can guarantee different results from what is desired and no consistency from run-to-run. Control must be accounted for, or expectations will be dra- matically lowered. Artwork that is inherited from the customer and processed without re-separation to your press parame- ters will create unpredictable outcomes, so ask your customer about doing a reseparation and including pertinent targets. www.flexography.org november 2012 FLEXO 39 To achieve consistency and avoid guesswork for the operator, targets must be in the artwork, or the operator will not be able to control the process.