Inkjet Adoption in Commercial Printing

Posted on by Dave Erlandson | No Comments »

As I mentioned in a previous blog (link) the print volume of color inkjet comprises over 50% of the page volume of color digital pages in the production market in North America. While this growth has been impressive, it is only phase 1 for the adoption of inkjet technology.  This phase is characterized by 4 color printing of documents with medium image quality requirements and low coverage on uncoated stock, which means transactional statements, books, and direct mail letters.

Phase 2 encompasses the ability to print with offset like quality and high coverage on standard offset coated/glossy stocks with ink prices that raise the breakeven point to at least 10,000 sheets for cutsheet or 5000 catalogs or magazines for web production. We are just at the beginning of Phase 2. Inkjet products aimed at this market and available for purchase today include:

  • Canon ProStream
  • HP PageWide Presses with HDNA
  • Kodak Prosper
  • Ricoh VC60000
  • Screen Truepress 520 HD
  • Xerox Trivor 2400
  • Fujifilm J Press 720
  • Komori Impremia IS29
  • Konica Minolta Accurio KM-1

Today we’ll take a closer look at the Kodak Prosper inkjet technology and how this technology helps enable Phase 2.

At the broadest level, inkjet technology comes in two flavors: drop on demand and continuous. In the list of products above only Kodak uses continuous inkjet technology.

Drop on Demand (DOD), as the name implies, involves emitting ink from the print head only when it is needed and where it is needed. The mechanism for ejecting drops is either piezo or thermal. Piezo is an electromechanical action where in an electric charge is applied to a piezo crystal causing the ink to be squeezed out of the head. Whereas thermal involves a small thermal explosion (boiling) inside the print head to force the print out. HP uses thermal drop on demand while all the other DOD suppliers use piezo.

Now when a printhead is not printing (which happens frequently in DOD) the ink, because it’s water-based, will start to dry. If the ink dries on the orifice plate or the nozzle, the dried ink will interfere with the next drop emitted. To get around this problem ink jet makers do a variety of things such as spit lines that force the head to print and in their ink formulation they add oil-based wetting agents, such as glycerin or glycol that slow down the drying of the ink and therefore reduce the chances of clogging. And they tend to work quite well.

The issue with wetting agents, as their name implies, is they don’t dry. As you put more and more wetting agents on the paper, it gets more and more difficult to dry the inks. And if the paper is not particularly absorbent, like a coated or glossy sheet, then the ink can pool on the surface causing a coalescence effect, which is a grainy or mottling look where the ink starts to clump together on the paper. This is why the makers of DOD presses often will limit speeds and ink coverages.

Continuous inkjet technology is different in that the ink drops are being continuously emitted. If DOD technology is like a squirt gun, continuous inkjet is like a fire hose. It’s always shooting ink out. Ink that is not intended for the paper is deflected to a catcher basin and then filtered, recirculated and brought back into play.

Kodak’s continuous inkjet technology is branded Stream. With Kodak’s Stream technology the drops are deflected using an air flow that deflects drops based on their size. Kodak’s printhead creates large drops that are intended to fall to the paper and the smaller drops that are not intended to reach the paper are deflected. Because ink is always flowing from the printhead there is no reason to add the same concentration of wetting agents to the ink formulation, which allows Kodak inks to print and dry on coated or glossy papers better than via drop on demand technologies.

In addition to their ability to formulate inks with less wetting agents, Kodak has also developed a clever drying system that uses interstation drying. Interstation drying simply means they dry between each inkjet line of heads. So they print a color and dry, print a color and dry, etc.  This allows them to print more ink on the substrate than anyone else. Everyone else is printing all their colors at once and then drying begins. When all colors are printed at once the paper is more prone to becoming oversaturated and often manufacturers will limit coverage and speed.

Kodak’s drying architecture is also unique in that it uses a near infrared light source. It is a high intensity and intelligent drying system. It focuses energy on to the printed portion of the page.  A Prosper press can evaporate up to 3 liters of water out of the press each minute when running heavy coverage jobs.

Because of high speed and unique ink formulation they are able to give customers a productivity advantage and a running cost advantage that allows them to move the crossover points higher. Book printers are finding the breakeven with offset for 300 A4 page books at 4000 to 4500 copies. And for magazines and catalogs the crossover point for a 112 page magazine with 66% color coverage, including many photographs and other high quality images is roughly 6000 copies.

Kodak’s design goal for inkjet is to replace offset and the first target is to migrate work from web offset presses which requires high speed. With 65 presses installed worldwide Kodak customers have been printing for years on coated stocks with water-based inks and at high speed. Slow speed for Prosper is 200 mpm or 650 fpm and high speed is 1000 fpm. Kodak Prosper press customers typically will average 20 million pages per month and can run up to 100 million pages per month on one press.

Kodak sells three models of the Prosper press:

  • Prosper 6000C aimed at the commercial market with 4/4 printing and 8 interstation dryers – great for printing heavy coverage on coated stocks.
  • Prosper 6000P – for the publishing market – has 6 interstation dryers and is best for printing on uncoated stocks.
  • Prosper 6000S – simplex version which can be sold as a standalone press or can be mounted in-line with a flexo or offset press for hybrid printing. Hybrid printing is being used in security printing, lottery printing, publishing, commercial and packaging. Packaging is a high growth area for hybrid printing.

In addition to selling Stream technology within their presses, they also sell the technology as imprinting systems with standalone print heads that get mounted on web offset or flexo print lines. They have nearly 1500 Prosper heads installed and they come in four models:

  • Prosper S5 – 500 fpm
  • Prosper S10 – 1000 fpm
  • Prosper S20 – 2000 fpm
  • Prosper S30 – 3000 fpm

We’ll save discussing hybrid applications for another time, but it’s clearly a strategy that has been employed throughout the industry and for many years. Before selling Prosper heads Kodak installed over 5000 Versamark heads.

As the second phase of inkjet adoption begins, it’s clear that continuous feed inkjet has a role. Today it has been implemented by Kodak via its Stream technology and is aimed at the high volume, high coverage end of the market standalone presses, hybrid presses and imprinting systems.

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