The new frontier for production inkjet is high-quality, high-coverage, graphic arts applications. The challenge in this market is to precisely place high amounts of liquid ink onto porous, and non-porous, materials and dry them at high speed without damage. The very small number of presses serving this market is a testament to the difficulty of meeting this challenge. Today, we have a new entrant with a unique approach to delivering quality while driving up the economic equivalent order quantity between inkjet and offset.
The KODAK PROSPER ULTRA 520 four color, web-fed inkjet press takes to the graphic arts field with some key differentiators. At 500 feet per minute (FPM), the PROSPER ULTRA 520 Press is the fastest in the graphic arts sector on coated stocks. Most importantly, it delivers its full resolution at top speed, consistently for all paper weights and supported grades. While all presses in this category use aqueous inkjet, this is the only one using Continuous Inkjet (CIJ) printheads - specifically, the latest generation of KODAK ULTRASTREAM Inkjet Technology printheads that leverage electrostatic deflection to increase jetting speed and reduce the size of the print array. It is also differentiated by its use of proprietary, hardware-based screening technology to drive speed, performance, and image clarity. Let’s look at how all the components of the PROSPER ULTRA 520 Press come together to make moving volume from offset to inkjet more attractive.
Delivering offset quality
Among the factors that drive our perception of quality are resolution, drop size, drop uniformity, and color gamut. Resolution alone can be a deceptive indication of quality, particularly when a press supports resolutions that are higher or lower at different speeds or on different substrates. The PROSPER ULTRA 520 offers a constant resolution of 600 x 1800. Factors such as the size and placement of drops must also be considered in the context of the stated resolution. Even the highest resolution press won’t deliver great image quality if the drops are irregularly shaped or inaccurately placed. Kodak prefers to describe image quality in terms of lines per inch (lpi), the term most used by offset professionals. Kodak’s claim of 200 lpi print quality is based on benchmarking against sheet-fed offset using a Kodak platesetter with KODAK SQUARESPOT Imaging Technology. While a focus on lpi reduces the need to dig into the ways that resolution, drop size, gray levels, and bit depth work together, I want to take a moment to focus on drop formation and accuracy.
It should be self-evident that, when drops aren’t exactly on target, images can become blurry, and edges can lose their sharpness. What may be less evident is the effect of the shape and uniformity of the drop. When a drop is perfectly round, and smaller than four picoliters, it can deliver precise results. Drops with trailing satellites or artifacts suffer from some of the same challenges as inaccurately placed drops because some of the ink is trailing the target area for that drop. Satellites can form when the drop is hit by the air drag of the paper moving beneath the print head. The slower the jetting velocity, the more impact air drag will have on drop formation.
KODAK ULTRASTREAM Inkjet Technology, which is the foundation of the PROSPER ULTRA 520 Press, places 3.75 pL drops precisely and without satellites. Unlike drop-on-demand printheads, CIJ printheads produce a curtain of drops inside the printhead. With ULTRASTREAM heads, some drops are printed while others are electrostatically deflected. Each drop has the opportunity to “tailgate” on the drop in front of it and doesn’t experience any drag or loss of velocity until it leaves the printhead. While the ULTRASTREAM heads fire at a greater distance from the substrate than other presses, they also fire with three times the momentum. The added momentum and throwing distance have the benefits of preventing dust from flowing back up into the heads and protecting them from substrate irregularities.