PFFC - December 2007 - (Page 14)

PROCESS MANAGEMENT The 7 Deadly (Converting) Sins here are some basic problems that crop up over and over again, with costly results in wasted time and materials. Below are examples, in capsule form, from my own experience in flexo printing. 1. Viscosity Management We all know the importance of running a job at the correct ink viscosity, but the most common instrument used for measurement—the efflux cup—has limitations. Because there is variation among suppliers and within batches of cups from a specific supplier, a calibration procedure has to be in place to make sure each cup is standardized. Also, use the correct cup for the correct viscosity range in use. Efflux cups are subject to wear and damage, so check cups periodically and replace those out of calibration. Another point to remember on viscosity is that the reading is dependent on temperature, so always make sure the ink is at operating temperature before measurement takes place. T Rubine is “Red 57:1” and is a unique molecular structure. The molecular structure defines the actual color and other properties associated with the pigment. If you lose track of pigment management, you run the risk of conditional color matches, color fading, and other physical and chemical instability. Work with your suppliers to become familiar with pigments in the inks you are using. When a packaging end use changes, make sure the pigments are up to the job. 4. Humidity Effects Ink suppliers can advise on appropriate solvents for use in summer conditions. However, attention to chill roller settings and dew point often are overlooked, and the web is rewound with condensate on the ink surface. Blocking and sticking can occur, particularly on treated films. By David Argent Contributing Editor Converting “sins” are many & they’re out there, waiting to happen. 2. pH Control If you’re using water-based inks, pH control is critical. Normally, pH will drift lower due to loss of amine from the ink. This will cause the ink viscosity to climb. Therefore, pH must be in the correct range before making any viscosity adjustments. Do it the other way around and you risk spoiling the ink. If pH is adjusted too high, the ink can become so alkaline that some pigments, such as rhodamine, can burn out. 5. Film Treatment Corona discharge treatment can be overdone, and over-treatment can hurt ink adhesion by degrading the film surface. Thus, it is important to control the treatment power applied to the film. 6. Ink Additives There may be two sets of ink additives in use, the official set that management knows about and the secret set in actual use! Each shift may have its own protocol for additive use. Audit ink additive use regularly and correct as needed. 7. Process Capability There are occasions when a print job is approved by the customer only after numerous machine and ink adjustments. The danger here is that this job always will be difficult to run at acceptable levels of quality, waste, and line speeds. 3. Color Control This area can be a minefield of potential problems. Besides the obvious issues caused by running off-shade product, there are other problems lurking from inappropriate use of pigments. In could add to this WHITE INK:COST listI’m sure youown experience. the Januray 2007 issue, the column from your MANAGEMENT on Color Measurement and Control Converting “sins” are many and explained that pigments are discrete they’re out there, waiting to happen. chemical entities. For example, Lithol Be careful! COMING NEXT MONTH Process improvement expert David Argent has 30+ years of experience in process analysis with particular emphasis on ink and coating design and performance. Contact him at 636-391-8180; djvargent@sbcglobal.net. 14 | DECEMBER 2007 WWW.PFFC-ONLINE.COM http://WWW.PFFC-ONLINE.COM

Table of Contents Feed for the Digital Edition of PFFC - December 2007

PFFC - December 2007 Table of Contents First Glance From the Editor Web Lines Process Management News Clips Narrow Web & Label Reporter Narrow Web & Label What’s New Products Carton & Box Reporter 2008 Calendar of Events Materials Testing Pilot/Lab/Technical Facilities What’s New Products Services Directory Classified Marketplace Advertisers Index Experience Speaks

PFFC - December 2007

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