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FLEXO Magazine : August 2009
TECHNOLOGIES & TECHNIQUES Printer: Date: Prepress Supplier: Imaging Device: RIP Software: Plate Type: Screen Family: Device Curve: FFTA FIRST Press Operating Data Sheet - Up To 8 Colors City / State / Prov: Country / Time: Prepress: Film Type: Laser Type: Dot Shape: Comp. Curve: Line Screen: Plate Height: Resolution: Number of Lasers: Cell Pattern: Micron Size: Plate Relief: Plate Processor: Temperature (Units): Humidity: Press Room Information: Print Process: Press Manuafcturer: Machine Age: Machine #: Maintenance: Press Crew: Metering System: Ink Vendor: Ink / Base: Din. / Zahn #: pH Device: Mounting: Tape: Cylinder Repeat: Blade Manufacturer: Blade Material: Blade Type: Substrate: Substrate Spec: Substrate lbs: Substrate Lot: Station / Deck: Color: Density: Viscosity: pH: Dryer Temp: Anilox Number: 1 2 3 4 5 6 7 8 Once all the samples have been collected and measured, and statistics calculated, a report should be generated that summarizes all of the key attributes of the press performance. This report is then used for both internal and external purposes. For internal purposes, it will provide useful information for the appropriate adjustments to be made in prepress (for color calibration purposes) and set the target run conditions out on press for the impending production job. For external purposes, it can be used to communicate process capabilities and limitations. This is helpful for designers and customers in developing graphics—for example, defi ning minimum type size and line weight. Also, by communicating process control limits, the report can lay the groundwork for customer release specifi cations that are in alignment with process capabilities. A sample press operating data sheet. else on each side of the target to aid in accurate scanning. These are generated along with the target from within the vendor’s application. The same story goes for characterization as it does for fi ngerprinting in terms of running the press under normal operating conditions. Again, nothing special or out-of-theordinary should be done when printing the characterization target. The way the test form is run should be the same as if it were a production run. HOW MANY PRESSRUNS? As one reads through the methodology steps of optimization, fi ngerprinting, and characterization, it’s fair to ask how many separate test forms and pressruns are needed to effectively set-up the conditions for the successful running of the production job. Given the expense associated with not producing saleable product, it’s not the most desirable situation to have to conduct a bunch of pressruns. And while it might very well be necessary to conduct numerous pressruns to identify and optimize the proper materials and settings, it’s very possible to accomplish everything in one shot with one test form in an afternoon’s worth of work. What’s hopefully obvious, though, is that the test form needs to include all the necessary targets and test elements to evaluate the process for optimization, fi ngerprinting, and characterization (if so desired). Then, samples can be produced that will address all the issues so that conditions are set for the production job. Good planning, some experience with the materials and variables, and a little bit of luck all help to make this possible. DATA COLLECTION & DOCUMENTATION It is important that enough samples are collected, so that a meaningful snapshot of the process is achieved. Under-sampling can lead to inaccurate fi ndings and adjustments that are off the mark. This can then lead to determining target conditions for future pressruns that are not achievable because they don’t accurately refl ect how the process behaves. Therefore, it’s best to collect multiple samples over a period of time to get a good sampling of the natural variation of the process. The general rule-of-thumb is to collect at least 25 random samples. From those samples, various statistics can be calculated (averages, standard deviations, etc.) along with upper and lower control limits, as was mentioned earlier. And depending on the nature of the analysis, fewer samples may be utilized, as was described for measuring characterization targets. 36 FLEXO AUGUST 2009 www.flexography.org It is also very important at this stage to verify and document all of the materials and press settings during this run. These should be listed on a press operating data sheet that can be issued with every job. FIRST 4.0 contains sample forms on the enclosed CD that can be customized for specifi c applications. Now that the work of fi ngerprinting and characterization has been completed, it’s time to utilize the fi ndings to prepare for the upcoming production run. Prepress will be able to make the necessary color calibration adjustments, whether cut-back curves or profi les and color management are used, so that the production pressrun can match the approved color target. At this point, the only thing the pressroom should have to concern itself with is repeating itself and controlling the process. Tune in next month to follow this imaginary job through to the production stage where process control and improvement come into play! ■ ABOUT THE AUTHORS: Michelle Warfford Beuscher earned a Bachelor’s (1989) and Master’s (1997) degree in Graphic Communications from Clemson University. She has been involved in the fl exographic printing industry since 1990, working in both wide-web paper and fi lm applications. She served on the FIRST Committee for the premier and second editions and as editor of the third edition. Currently, Beuscher is an independent consultant to the fl exographic industry specializing in training program development and implementation, printing process measurement, control and evaluation. She served as project manager and editor of FIRST 4.0. For more information, contact Michelle at firstname.lastname@example.org. Bill Pope is technical director for FTA. FIRST 4.0 Get Your Copy Today! FTA Members: $99.00 (Non-members: $198.00) Place your order online at www.ftastore.com or call FTA at 631-737-6020.