In the case of high-speed inkjet web presses (see sidebar), such as HP’s T series and Kodak’s Prosper, the front ends are quite robust. Some printers even “are adding multiple blade servers” to these devices, notes Hamilton, for ultra-high processing power.
Start Fast, Finish Slow?
What other factors come into play when determining realistic speeds? There are back-end production concerns such as the dreaded bindery bottleneck. Inline finishing can slow down the process. “Most products are designed to match machine throughput,” Xerox’s Mueller notes, such as stackers. But, he adds, “other mechanical actions—like gluing, jogging, punching, and folding—take time and can lead to low production.”
Mueller cites the example of a dual stapled set producing a job requiring two-page sets with dual staples. “We’d have to skip a pitch [panel or frame] to compensate,” effectively cutting productivity by one third. “When selecting finishing actions, users should be aware it can significantly impact productivity,” the engineer stresses.
The “Really Smart People” at Xerox and its Palo Alto Research Center (PARC) have conducted a lot of impressive research over the years, but one thing they haven’t figured out (yet), jested Mueller, is how to alter the laws of physics.
While inline finishing can optimize labor and offer less user intervention, HP nonetheless typically recommends near-line finishing systems. “With inline, you’re only as strong [or fast] as your weakest link,” Martinez says. “Near-line makes [adding] redundant systems easier.” A finishing line independent of the press is ideal, he added, because if it goes down the press can keep printing. “It can also be shared across multiple printing devices.” An existing offset printer already may have an offline bindery, he added.
The bottom line for printers calculating pressroom productivity: Keep in mind that you can seldom rely on manufacturers’ speed ratings. OEMs “tend to be either overly cautious or overly optimistic in most cases,” warns Colorado-based dealer Star Graphic Supplies. “Certain presses…were rated at speeds much higher than they could ever actually run and produce salable work.”
The Different World of Inkjet Web Presses
The big inkjet web presses are a different print animal, obviously, whose rated speeds are measured in feet, not pages, per minute: up to 400 feet-per-minute (fpm) in both monochrome and color for the HP T300 with its 30-inch roll. Unlike their cut-sheet cousins, heavier stocks don’t pose such a challenge for inkjet webs, but heavier ink coverage does.
“There’s really no box slowdown because of paper weights,” notes Moisha Clark, HP’s North American category manager of the high-speed inkjet web press. “The real question with these presses is, what kind of density do I want to put down on the paper and how fast do I want to go?” The key is having the right number of dryers, Clark adds. Using the T300 as an example, speeds slow to 300 fpm when color is more critical and higher ink densities are required. Even with a 25 percent production reduction, that’s still churning out high multi-million-quantity monthly impressions at a fast rate of speed. And much like an offset press, “operators have the ability to dial it [speed] down, if they want, for slightly richer color.”
Even the financial model is different, explains Clark, who spent 17 years on the Indigo side. “Customers incur a click charge on the Indigo every time the cylinder goes around. But with the T200, T300, T350, and T400, it’s based on how much ink you are laying down.” Still, HP’s 70 percent utilization rule applies for its inkjet web ‘lab’ speeds, too, accounting for job change-overs, preventative maintenance, human factors, and other production variables. In the real print world, a rated speed of 400 fpm translates to approximately 280 fpm.
Here, also, “finishing is a huge conversation with customers,” Clark adds. “One size does not fit all. We can deliver at full speed, but can a said [finishing] manufacturer accept it? A lot can. We have great finishing partners.” But again, it depends on what kinds of jobs you’re running. “Can a dedicated finishing line adapt to different sized applications?” asks Clark. “Or is it one size frequently, such as books, and you’re running the doors off?” HP’s approach to finishing is highly consultative. “It’s not just about the box,” he emphasizes. “It’s the end-to-end solution.”