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FLEXO Magazine : June2010
It’s the only thing that all printing has in common—the need for a substrate. Yet not all substrates are created equal. Just as with the print process itself, substrates come with variables that can lead to undesired inconsistency in the print results. Substrate Session chair Rick Rosenberger (Solo Cup Co.) assembled a panel of experts on Monday, May 3 to tackle these issues. Do your substrates slip or grip? James Ford of Color Resolutions Inc. helped attendees with substrate troubleshooting problems with a thorough examination into the na- ture of friction. He talked about the different types of coefficient of fric- tion (COF)—static and kinetic—as well as different measurement types (horizontal and inclined). Ford further discussed the numerous causes of variation in COF: • Substrate Type • Paper (Coated or Uncoated) • Film (PTFE, PE, PP, PS, etc.) • Surface Directionality • MD (Machine Direction) • CD (Cross Direction) • Surface Contamination—contamination (fingerprints, etc.) may result in effects of more than 30 percent. The latter of those elements—surface contamination—Ford proclaimed to be the biggest of the issues, and can result from oil from knives, fingers, dust and more. Coatings and additives, he cautioned, can also play a role in changing and varying friction. Changing gears, Enercon’s Rory Wolf took the stage to discuss the evo- lution of surface treating technology, and then some of the latest advance- ments. The goal of any pre-treatment, according to Wolf, is managing emul- sions and interfaces. Static charge can also affect adhesion, he noted. Wolf highlighted some of the limita- tions of current treatment technology: • Boundary layer air not sufficiently removed at high speeds. • Backside treatment creates ink picking. • Tribocharging effect on ink spidering not neutralized. • Ionized air (ozone) or plasma gases entrained with web. • Limited removal of low molecular weight organic surface contaminations. • Splices and varying material thicknesses require manual gap adjustments, reducing productivity. • No new solutions with integrated sustainability. The latest generation of atmospheric plasma treaters, Wolf explained, overcome many of those limitations by removing boundary layer air effect, neutralizing tribocharging/ink-spi- dering effects, offering higher discharge concentration and less maintenance/damage from material thickness variations. Speaking on behalf of the paper mills, Steve Rote of M-Real revealed what mills have done to keep up with demands of paper printers and converters. The fact is, many times corrugated printers must match the outside of the box to the package (a film substrate or label) on the inside. The bottom line, according to Rote: garbage in, garbage out. “Toler- ances at the mills have tightened to meet demand,” he said, noting that more coating does not always mean more holdout. Rote also reviewed some tips that he has been giving a lot of board converters. For one thing, he said, “If you have washboarding, it ’s because you have too much starch.” More often than not, minute changes in your process can mean the difference between OK board and good board, Rote insisted. He advised lowering boiler temperatures, lowering steam pressure, and lowering starch consumption. Looking at the relationship between substrate and plate, Bob Hannum of DuPont Packaging Graphics talked about how one change in the plate package—mounting tapes, plate type/thickness/durometer, sleeve/mandrel, etc.—c an cause big problems. Surface energy of a plate, it turns out, does not have a major impact on dot gain or print quality. But durometer—plate hardness—does. In fact, he recommended a hard durometer plate with a firmer cushion for dot gain and good solid ink density. For corrugated printers, though, he proposed the biggest factor to be in dot shape. The ideal dot is a hybrid of digital and analog shapes—a flat top with steep but strong shoulders. n Paper, Film and Folly Substrate Session Troubleshoots Consistency Issues FTA TODAY Revealing the Future of Print to Package and Specialty Printers A Customized Trade Show for the Americas • Worldwide introductions of the hottest new technologies • Live equipment demonstrations of the latest applications and workflow solutions • Learn something new—over 50 seminars in 20 education categories • Network with industry experts and peers Explore Equipment & Products of Interest to YOU 1899 Preston White Drive, Reston, VA 20191 USA | T 703.264.7200 | firstname.lastname@example.org | www.graphexpo.com • Flexible Packaging • Labels: Tape, Tags, Film & Foil • Converting • Folding Cartons • Digital Printing • Flexographic Printing • Components/Computerization Discover Special Show Floor Features Back by Attendee Demand! A Returning Show Floor Destination! PLUS—The latest breaking news on Printed Electronics and RFID 16 FLEXO june 2010 www.flexography.org • Surface contamination is the largest perpetrator of major friction variation. —James Ford, Color Resolu- tions Inc. • Managing emulsions and interfaces is the goal of all surface treatment. —Rory Wolf, Enercon. • Washboarding on corrugated substrates is most of- ten caused by too much starch. —Steve Rote, M -Real. • A hybrid digital/analog-style dot is the best solu- tion for high-quality board printing. —Bob Hannum, DuPont Packaging Graphics. Ford. Wolf. Rote. Hannum. FLX_June2010_mech.indd 16 6/10/10 9:38 AM