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FLEXO Magazine : June 2009
TECHNOLOGIES & TECHNIQUES The CI drum allows for greater registration than on an in-line press. Photo courtesy Comexi North America. The in-line format allows for creative confi gurations and insertion of modules between or above print decks. Photo courtesy Mark Andy Inc. Pros and Cons: In-line Web Flexo vs. Central Impression Flexo for Folding Carton Printing S ize matters. When it comes to printing cartons, the size of the web width can be determined by any number of factors, including, but not limited to, the existing web widths handled by an operation, the expertise of current staff, and the desired end-use applications. According to some experts, fl exography is the future of folding cartons and cartons Press Characteristic or Capability Backside printing Color-to-color registration Ease of die cutter integration Floor space utilization Advantage In-line CI are the future of fl exography, as it’s one of the few markets that the process has not yet thoroughly penetrated. FLEXO asked experts from both wide web central-impression (CI) and narrow web in-line press manufacturers to weigh in on the advantages and disadvantages of each. Below is the result of their musings. Explanation It is far simpler to fl ip a web and print the backside with a reversing deck on an in-line press. This has been done on a CI, however it is neither commonly done nor simple to do. Since the web is pinned tightly on the CI drum, most of the printing variability induced by an unsupported web is removed. With the advent of direct drive gearless technology, registration accuracy is negligible, even during acceleration and deceleration. Gearless technology is common on in-line presses but one should consider that the web remains unsupported between each station. However, a quality in-line press can hold register tolerances that are well within the commercial standard for paperboard packaging. In-line Although there does not seem to be any sound technical reason for this, integration of die cutting is more common with in-line presses than with CIs. As a result, there exists more expertise and general competence to effectively carry out the integration within the supplier base. This gives converters more capable resources to draw from, making this a more effective technique in the context of an in-line machine. CI The utilization of fl oor space is an important factor when evaluating equipment. The CI press concept (all print decks arranged around a central impression drum) lends itself ideally to any consideration of plant space and will generally afford a smaller footprint than a comparable in-line press. This also translates into the saving derived from the related cost of machine installation (see purchase price). Hot air drying In-line For water-based inks, a CI press offers very little space between print units to put a hot air dryer. For aqueous coatings, the CI press requires a separate downstream coater. The in-line’s design allows for almost unlimited space up above the print heads so water-based inks and coatings can be dried effectively at high speeds without wet trapping. 18 FLEXO JUNE 2009 www. f le xography. org CARTONS
Sustainable Spring 2009