Getting a Head in the Game

This conceptual diagram shows the basic process, in order, of a thermal, piezoelectric and continuous inkjet head.

Inkjet still is used as a 
generic label for the latest class of digital production printing systems, but as the number of products in the market continues to grow, so too does the range of imaging technologies employed. This is a marked change from the decision potential buyers have been presented with in the electrophotographic (EP) press category. While there are competitive differences in toners, fusing systems, paper paths and more, the imaging technology is fundamentally the same.

In this aspect, inkjet is more akin to traditional offset technology than other digital printing solutions. Choosing between the standard, UV/hybrid, waterless, heatset and non-heatset variations of offset carries implications for the capital and production costs, stocks that can be run and applications produced.

Differences in the inkjet imaging systems now being employed can have an impact—to varying 
degrees and relative to each other—on head cost, failure rate and cleaning/maintenance requirements; substrate flexibility; print resolution; color saturation; print width; and more. It doesn’t quite rise to the level of an apples to 
oranges comparison, but the technology has very distinct flavors.

Thermal and piezoelectric drop-on-demand (DOD) inkjet imaging systems were at the heart of the first web inkjet presses to be commercialized. Examples included the HP T200/300/350 series of thermal machines and, on the piezo side, the Océ JetStream family, Truepress Jet520/EX/ZZ line (as well as Ricoh/InfoPrint Solutions’ InfoPrint 5000 implementations of the technology), and the Kodak Versamark VL-
Series. Then came Stream continuous inkjet with the Kodak Prosper line, and now phase-change technology with Xerox scaling it up to a production-class implementation.

As a quick recap, thermal and piezoelectric inkjet both fall into the drop-on-demand category, meaning a drop of ink is only produced when needed for printing. DOD heads, particularly thermal, have benefited from a cost advantage because of their engineering and mass production. The heating required for thermal units restricts ink formulations, while piezo heads are more mechanically complex.

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