Estimating Folding Time
Q: We seem to make a lot of mistakes in estimating folding time in our in-house bindery. How do the pros do it?
A: Folding rates are a function of the speed the manufacturer built into the machine, the characteristics of the paper being run, and the degree of difficulty of the folds.
If your folder's rated speed is 7,000 inches per minute, and the sheet you are folding is 11" long, add 10% to the length for the sheet gap, and the following formula gives you the number of sheets you can fold per hour:
7,000" ÷ (11" + 1.1") = 578 sheets per min. or 34,680 per hr.
That's if the stock can take the stress of running that fast; usually newsprint, recycled paper, and light weight stock cannot; neither can coated or heavy stock. Factors such as curl and static will also slow down production.
If your 8 1/2" x 11" sheet is to be folded in thirds to a #10, the job lends itself to being run 2-up on a 17" x 11" sheet, thus doubling your output to almost 70,000 finished pieces per hour. At this speed manning would probably be one loader and two catchers.
But we figure the maximum speed of parallel work on a 7,000" per minute folder is 5,500" per minute.
And for right angle work, real-world speed is 3,500" to 4,000" per minute. So if you have a 16-page signature on a 23" x 25" sheet of 60 lb. paper, you should figure on running 4,000" per minute, giving you this calculation of output speed:
4,000" ÷ (35 3.5") x 60 = 6,233 sheets per hour. We have occasionally run 16s at 11,000 per hour, but not often.
Other factors that can slow you down are imposition, slitting and chasing, split guides, map folds, gatefolds, trimming waste while running, gluing, etc. Make-ready times are significant, too-and hard to predict.
With the host of factors that can degrade folding speed, it's only our operators' years of experience that guides them in estimating how much speed will be lost for each of these factors.
Finally, keep this in mind: today's new machines are way ahead of machines manufactured 5 or more years ago. The older your equipment, the tougher it is to schedule reliably. We've ordered two new folders-one for signatures and one for maps-to stay on top of the technology.
-Marty Anson
Cleaning Ink Smears
Q: What solvent can I use to clean up smeared ink or setoff on coated stock without destroying the finish?
A: We've found that Trichloroethane is effective in removing unwanted ink marks on some matte and coated stocks. Put a little of it on a rag and dab the area that needs to be cleaned. It will dry quickly and leave little residue or smell.
Process Improvement Coordinator
Collating Marks
Q: How should a printer indicate to a bindery the correct sequence of signatures in a book block? I always try to do it with a carefully worded purchase order, but I've had problems twice-and one time it wasn't caught until after half the books were bound. (Ouch-expensive!) If I'm going to use Bindagraphics, how can we make it crystal clear to your people?
A: You should use collating marks.
The collating mark is a short line, about 1/2" thick, printed on the back (spine) of each signature. You strip them in such a way that, when the signatures are folded and gathered into a book block, the marks always appear as a series of steps descending from the head.
Use of collating marks gives the bindery a clear visual guide to the correct sequence of signatures. They are especially important when the signatures have no folio numbers.
Although adding collating marks to your signatures will cost you a little time in stripping, they will eliminate any confusion in the bindery, and that will prevent the kind of problems you say you've had before... a good trade-off, when you consider the expense of clearing up confusion after the fact.
Adhesive Binding Supervisor
"Never-Dry Blue"
Q: Please take a look at the enclosed sheet my company printed and tell me if you can figure out why the color's so bleached-out and there's so much ghosting on the back. This sheet looked fine right after the finisher we sent it to UV-coated it, and his people are stumped as to why these problems showed up a week or two later.
A: Your sheet's got the Reflex Blues. UV coating specialists at Bindagraphics call reflex blue "the never-dry blue" because something in its pigment seems to react gradually with something in the UV varnish, so color fading and ghosting can develop for days or weeks after the job is coated.
You can reduce the problem by allowing plenty of time for your sheets to dry before UV coating, but even this is no guarantee. To be on the safe side, we advise avoiding inks with reflex blue in them on sheets that will be UV coated. (And be careful-a lot of PMS colors include reflex blue.)
Stamping, Embossing & Die-Cutting Supervisor