Sign & Digital Graphics

September '14

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S I G N & D I G I T A L G R A P H I C S • September 2014 • 55 the ink has had some time to spread and dry. If nozzles misbehave by either failing to print or by landing where they don't belong the effect on the print is mitigated by the blending of dots from different scans avoiding the appearance of light or dark lines. With fixed array printing you get only one shot at placing a drop where it belongs, or if not you may see the results in print defects. So you must now deal with wet-on-wet printing since adjacent ink drops are printed within a very nar- row window of time and you must have either high reliability or built-in redun- dancy (preferably both) to avoid obvious defects. With scanning arrays the nozzles are serviced when the printhead array is off to the side of the media. So uncapped printhead performance in fixed array sys- tems becomes even more critical since the printheads are never off to the side. Memjet achieves reliability by using redundancy. They use extremely small drops (less than 2 picoliters) and build up the print using multiple drops from multiple nozzles. Individual drops are not visible to the naked eye, so if one is misbehaving it cannot be seen. In addi- tion the Memjet system uses water-based dye inks that have very low solids con- tent (only a few percent by weight) so solids buildup on the printheads is less of a problem. However, HP uses larger drops and pigments in their water-based inks, which makes it even more difficult to achieve high reliability because of the higher solids content in pigment inks. To achieve their goal of a fixed array HP had to invent some new ink technology. The Inks Unlike scanning array systems, in a fixed array system the nozzles often 800.258.0991 Imagine the Possibilities DigiMaxx™ is the first and only super-wide printable magnetic media made exclusively in the USA—now available from Magnum Magnetics in widths up to 48" and supported by our outstanding customer service. Print directly to super-wide magnet to create stunning retail signage or colossal wall graphics that really stick!

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