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Do you have an above-average PQ?

Apr 1, 2001 12:00 AM

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Nobody's perfect, but most makereadies can be a lot better

The pressroom is the investment center of most printing operations. It's evident from the balance sheet as well as from a plant tour. Senior management, seeking to improve overall ROI, will find a world of opportunity here. Pressroom managers are well advised to start looking at increasing throughput and press utilization rates just as they have traditionally worked at job cost and spoilage reduction.

There's no better way to start than to calculate the Productivity Quotient (PQ) for each press in the room. Calculating PQs starts with a calculation of the Productivity Potential (PP).


This is as simple as determining what revenue could be produced from that press if it were maintained, operated and managed perfectly. This requires estimating how long it takes to produce the typical job, assuming that the plates are correct and waiting, that the makeready is minimized and that the press is swiftly accelerated to its rated speed. Of course, with preventive maintenance programs and expert roll preparation, we can expect minimum unplanned stops.

This perfect, typical job time is then divided into the number of available hours per year (say, 355 days @ 24 hours minus 15 percent for maintenance, etc. leaves 7,242 hours) to give the number of jobs per year. The result is multiplied by the revenue or signatures per job to get the PP for that press. It may be better from the pressroom perspective to express the PP in signatures or sheets instead of revenue, which involves factors well beyond pressroom control.

When the actual number of signatures from a given press in the past year is divided by the calculated PP, you have PQ. How does it look?

Our experience indicates that PQs are rarely above 60 and all too often below 50. While it's difficult to imagine a pressroom PQ that even approaches 90 or 100, it's equally difficult to see why raising PQs by 10 or 20 points isn't reasonable.

Maybe it helps to put web-press throughput opportunities in perspective. Paper is usually the single largest element in web printing cost — press spoilage (all paper thrown away at the press site) is an obvious target for cost reduction. If we assume that a reasonable objective would be to reduce spoilage from, say, 12 percent to 10 percent, and that paper represents 50 percent of job cost, we can calculate that these two points of spoilage saving represent a one percent reduction in total job cost.


Improving press throughput has huge potential savings. Consider the web printer whose typical run length might be 100,000 sheets and whose press is rated at 35,000 per hour. If the typical makeready is one hour, divided approximately between two-thirds static makeready (Makeready One) and one-third running makeready (Makeready Two) and the “cruise” speed is 30,000 per hour, that 100,000-sheet job will take 4.425 hours.

If a printer can reduce makeready to 45 minutes (30 minutes of Makeready One and 15 minutes of Makeready Two) and ensures that crews can run the press at 35,000 per hour, job time drops to 3.65 hours. This represents a 17 percent reduction in printing cost, excluding materials, which results in approximately eight percent reduction in total cost. When the Makeready Two spoilage reduction is considered, it amounts to an additional saving of approximately 1.5 percent of paper cost.

While these savings are impressive on both a comparative and absolute basis, the press cost-center throughput implications are even more impressive. Calculating maximum usable press hours of 7,242 hours per year, the typical 100,000-sheet job described above could be printed 1,637 times with the one hour total makeready and 30,000 cruise speed. If the makeready process is fine-tuned and the cruise speed is raised to 35,000, the job could be printed 1,984 times, a 21 percent increase in output from the same cost center, the same investment and the same human resources.

It's reasonable to estimate that web-press total job cost is at least 30 percent fixed cost if you assume that labor cost is fixed. Given that the press is to be crewed throughout the year whether it runs 1,637 jobs or 1,984 jobs, we think it's reasonable to call labor cost fixed. If 70 percent of the additional 21 percent of production is variable cost, then 30 percent of the additional 21 percent (30 percent × 21 percent = 6 percent) of production will fall to the bottom line. That's exciting, especially when it's compared with the traditional saving opportunities achieved by reducing paper waste.


Consider the effect and impact on the web printer's cost equation and throughput capability as run lengths fall further. The fine-tuning of makereadies previously described represented a 25 percent reduction in makeready time (from one hour to .75 hour). The cruise speed increase was only 17 percent (from 30,000 to 35,000). As the web printer's run lengths decline, the number of makereadies per year steadily increase and the percentage of total press time that the press is in cruise mode declines. Therefore, the leverage on the printer's cost equation of such a throughput enhancement program will become greater as run lengths decline.

It would seem that for web printers, mounting an organized assault on makeready time and costs is a no-brainer. With such a throughput program, either fewer presses are needed to match prepress and postpress/bindery capacity, or fewer additional presses are needed to handle the future job mix of shorter run lengths. Either way, the printer wins!

Best practices for web printers

Attendees at this year's Web Offset Assn. (WOA) Conference (May 6-9, Washington) have a chance to hear the latest news from the Web Offset Champions Group. The group will present highlights from “Web break prevention and diagnosis,” its second guide for web offset printers. The 33-page booklet helps users diagnose 140 web break and mis-splice causes, and identifies best practices to minimize their occurrence. (See “Improved productivity is a team effort,” April 2000, p. 52.)

The Web Offset Champions Group currently includes Aylesford Newsprint, Kodak Polychrome Graphics, MAN Roland, MEGTEC, Nitto, QTI, SCA and Sun Chemical. The group released its first guide, “Roll to web processing,” at Ipex in 1998.

An international group of printers reviews each booklet and provides feedback. North American participants include Quad/Graphics, R.R. Donnelley, Treasure Chest, Quebecor and Transcontintental World.

Following the WOA Conference, the group will also participate at Sun Chemical's European Printer Technical Seminar at St. Alban's University in Wisconsin. The subject will be “How to avoid surprises when changing paper grades,” the topic of the third guide currently being prepared. For more information, contact Nigel Wells at 011-33-169408993 or e-mail: