How real-world are full rated speeds? Minus about 30 percent, according to HP’s calculations, if you account for downtime. That’s what the digital press OEM tells serious shoppers when they get to the number-crunching stage. The HP Indigo 7500 press, for example, has a top rated speed of 60 ppm in color (4/4). However, HP manages the expectations of customers and hot prospects, cautioning them that they can expect performance somewhere “in the range of 65 percent to 75 percent of this utilization,” explains Rolando Martinez, North American category manager for the manufacturer’s high-end Series 3 presses. Instead of 60 ppm, “42 ppm is a more realistic number,” he acknowledges.
That said, Martinez also is quick to point out that some HP customers have utilization percentages at 80 percent and more. “There are just so many production factors to consider,” he says, and the fewer the variables, the faster the run. Martinez cited photobook customers who can run at 54 ppm (90 percent utilization) because there are no paper changes. Plus, he added, “a very experienced operator can achieve a much higher utilization.”
But don’t look for HP’s real-world ppm “utilization” numbers to be published in any marketing materials. You won’t find them there—not because rated press speed statistics are propaganda, but “because they vary too much,” Martinez says. “There would be too many footnotes.”
Secondly, these page-per-minute stats are based on A4 paper sizes. As Kevin Horey, VP of production products in Xerox’s Graphic Communications business group, put it, “Not many of our commercial print customers run an 8.5x11 [inch] piece of paper through [our digital presses].” David Mueller, Horey’s colleague, adds that 11x17 and 12x18-inch sheets, even those 19 inches wide, are more commonplace in production print environments. Fego, their competition at Konica Minolta, notes that “those 13x19 sheets are in the transport longer and the toner is working harder.”
RIPing through Data
Once you've optimized the system’s hardware, what’s the next step? The digital front ends (DFEs) or RIPs that drive digital presses must process data quickly enough to drive presses at their full rated speeds, Global Graphics CTO Martin Bailey told an audience at the IMI Digital Printing Presses conference last June. And it’s not only about speed, either. “The challenge isn’t just to be fast enough,” Bailey says. “The real challenge is to achieve that goal without incurring an uneconomically high cost for the bill of materials to build the DFE.”
Press manufacturers want to minimize the costs of the DFE compared with the cost of the press, he points out. Yet they have to ensure their products help print shops respond to market opportunities such as the growing market for photobook printing and personalized direct marketing materials. Bailey went on to discuss his firm’s approach to working with HP on its SmartStream Production Pro Print Server and Ultra Print Server DFEs. Global Graphics is the developer of the Harlequin RIP that has been used to drive the HP Indigo digital press range for the past 10 years.
For graphic-intensive projects and direct mail with complex variable data print (VDP) elements, particularly, “the RIP has to keep up with the data flowing into it,” notes Konica Minolta’s Fego. When it comes to rated speeds, there’s an assumption that the RIP is powerful enough so that the digital press doesn’t have to wait for printable data. (Another basic assumption is that the device is warmed up and ready to go.)
HP analyzes files in advance in a lab, performing capacity tests per application; their RIPs are scalable. Like most vendors, Konica Minolta offers a variety of RIPs, from basic embedded ones to Creo front-end server styles and its own proprietary RIP solution, which has been on the market for about one year. It even offers EFI’s high-end Fiery QX100 server for “extreme” production printing.
“You may need a different profile for different printed products,” adds InfoTrends’ Hamilton, depending on media thickness and coatings. In the case of EP printers and presses, for example, if someone is producing internal book pages on 24-pound text and then switches to 110-pound cover stock, the fuser needs to heat up and/or cool down, adding time into the equation and decelerating performance ratings.
Indeed, Xerox’s “mixed media mode can change the temperature of the fuser and have a direct impact on productivity,” agrees Mueller. “It’s a function of heating and cooling the thermal mass inside the machine.” A slowdown is inevitable to maintain image quality and fix, he explains, because “larger gaps are required between the paper [path] to allow the fuser to adjust temperature when switching between heavy and lighter weight papers.”