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Sep 1, 1995 12:00 AM
In many instances, estimators plan jobs based on the most economical way to strip, make plates and print, but this does not always lead to the best production method. Let's look at the following problem:
What is the best way to run 100,000 12-page self-cover booklets with a page size of 8 1/2 x 11 inches, one color black, two sides, on 70-lb. uncoated offset with no image printing within 1/2 inch of any edge, saddlestitched? The best available press is 25 x 38 inches, one-color sheet-fed. The bindery houses a 32-inch guillotine cutter, 26 x 40-inch folding machine producing three right-angle folds, and an inserter-stitcher-trimmer line with two double stitching heads and a five-knife trimmer.
The most straightforward way to plan the job is as two sixes sheetwise on a 23 x 35-inch sheet with two 8 1/2s out of the 23 and three 11s out of the 35. (Sheetwise means that one side of the job is printed from one plate, in this case the six pages including page one, which is called the front side. Then the plate is removed, another plate containing the back six pages is hung and the sheets are turned over and printed on the other side. In some parts of the country, it is called work-and-back.)
The above method requires only one-up stripping, two plates, two make-readies and 200,000 press impressions. In the bindery, no guillotine cutting is required, but 100,000 sheets must be folded and 100,000 booklets must be stitched one-deep.
However, some estimators would balk at the amount of paper waste - an extra 5 1/2 inches out of the 23 and an extra 1 1/4 inches out of the 35 - and look for another way to run the job. For instance, it could be one eight-pager run one-up, two-on work-and-turn, and one four-pager run two-up, four-on work-and-turn on the same 23 x 35-inch sheet.
(Work-and-turn means the front and back four pages are printed on the same side of a double sized sheet, and half as many sheets as the final quantity required are run. One side is printed, sheets are turned, the other side is printed and sheets are cut in half before being folded.)
With four 8 1/2s coming out of the 35 and two 11s out of the 23, waste almost is entirely eliminated. There would be two plates, two makereadies, two turns, 100,000 press impressions for the eight-page work-and-turn, plus 50,000 impressions for the four-pager two-up, four-on work-and-turn, making 75,000 sheets to cut in half, 100,000 eight pagers to fold one-up, 100,000 four-pagers folded two-deep and slit apart as they are folding, and 100,000 books to stitch one-deep.
Now let's try planning from back to front instead of front to back. The question becomes, "What is the best way to bind the job?" Can it be bound two-deep? Yes it can, by the following method: eight pages running two-deep on a 23 x 35-inch sheet with two rows of the same eight pages printing one above the other. It would fold as is, two-deep, without being slit on the folding machine. The four remaining pages still would run two-up, four-on work-and-turn, cut in half and folded two-deep without slitting.
Then the booklet can run on the inserter-stitcher-trimmer two-deep, which would save 50,000 stitching impressions. If the unit runs at 5,000 sph, 10 hours are saved. There would be extra makeready time of approximately one hour, reducing savings to nine hours, but on a system with an hourly rate of $100, it still equals $900 savings. Using this method goes beyond offsetting the additional plate and make-ready required by the second plan.
Naturally, we cannot be absolutely certain of the best method until calculating the cost each way, but it is clear that both estimators and computers need to be programmed to plan jobs from back to front.
Contributing editor. Merit is a production management and estimating consultant based in New York City