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Feb 14, 2002 12:00 AM
Some printers try to keep as much work in-house as possible. Do yourself a favor and keep the cutting and binding portions of your jobs together. This will reduce unproductive finger-pointing and increase vendor accountability. If printers cut jobs prior to outsourcing other postpress operations, they have by default accepted at least partial responsibility for the overall quality of the project. If their cutting is off, the folding and binding will be, too.
Unlike three-knife trimming, in which every side is uniformly cut, flat-sheet trimming is difficult to keep precise. What appears to be good cutting during a production run may not be so great once the product is collated and binding begins. At this point, small cutting variations between lifts may become noticeable and will undermine a high-quality appearance. Regardless of whether you’re comfortable with outsourcing, at least let those who bind your books cut them too.
PAPER AND INK ISSUES
In general, the harder the substrate, the more difficult it is to cut. Coated sheets with significant clay content have hard surfaces and require frequent knife changes, sometimes as often as twice a day. Recycled sheets can be difficult to cut because they contain a potpourri of paper fibers and miscellaneous waste. When cutting difficult stocks, it’s hard to get clean, consistent cuts throughout production runs--no matter what precautions are taken. When problems occur, determine if your paper is the cause. Do this by substituting a different stock to see if the problem disappears.
If reflex blue or other slow-drying colors are present on a sheet, brace yourself for more problems. If you use normal clamp pressure, you’ll likely get excessive ink offsetting. If you reduce clamp pressure to avoid this, knife draw problems will increase. Combat reflex-blue ink problems before the job hits the bindery: Dry trap-applied varnish usually works wonders.
SOME TECHNICAL TIPS
Logical layouts | When you lay out book jobs, think about how you’ll convert them in the bindery. For mechanically bound jobs, do more than line up common trim lines--make sure all pages flow in a logical sequence so your components will be in a production-friendly order for downstream operations. This may seem obvious, but on many occasions, our company has had to reskid poorly laid-out jobs after cutting.
Draw | The main causes of draw problems are: wrong clamp pressures, dull knife, wavy stock and a lift of paper that’s too thick. Knives need relief as cuts are made, or else sheets will be pulled. Full-sized lifts are fine for most porous stocks, but smaller lift sizes are best when cutting dense, heavily calendered paper with brittle clay fillers. To maintain high quality standards, reduce lift thickness routinely by at least 50 percent. Draw problems are especially noticeable on books with common images bleeding off pages, such as bars or lines. It’s important that printers work with bindery professionals who understand these tradeoffs.
Trim allowance | Even if your images don’t bleed, try to avoid single chop cuts. The inherent problem with chop cuts is you get one try--and that’s it. Once the cut has been made, there can be no more adjustments without reducing the final trim size. Cutting problems are magnified and affect folding accuracy and crossover image alignment. Whenever possible, allow at least a 0.125-inch takeout trim margin.
Trim allowance for tabs | Trim allowance is especially important when planning tabs. Unless your job planners work with tabs every day, it’s difficult to get tab copy positioned accurately for a single chop cut. Even though chop cuts save a few strokes on a cutter, the chance for poor quality and error significantly outweighs the savings.
True printers’ guide and gripper | As diecutting and foil-stamping experts know, easy identification of a press sheet’s true guide and gripper saves time and reduces errors. The same holds true for cutting. If a sheet is converted in the same direction as it’s printed, registration accuracy is much better. Sometimes guide and gripper sides are obvious, but at other times, they’re nearly impossible to identify.
Maps | Map quality depends on cutting precision as much as folding accuracy. When cutting maps, make sure your bindery accurately preflights your job. Thick maps with overhanging covers and outside panels that fold on color breaks look terrible if improperly cut. Take extra care when working on maps with 10 or more folds, because their front panels can easily appear short.
Gatefolds | Before beginning gatefold jobs, cut a makeready lift, fold it and make sure the gap in the center is the right size. If the gap is too tight, make adjustments. If it’s too large, and there are folds on color breaks, you’re stuck. If your bindery skips this step, they’re cutting with blinders on.
Mechanical-bound books | When cutting flat sheets for downstream collation and mechanical binding, make sure they appear as if they were three-knife trimmed. Unless you consistently cut all of your forms, books with common bleeding graphic elements will have page-position variation, which results in an unattractive "saw-tooth" jagged bleed.
Rotary scoring | When your job needs rotary scoring, score first, then cut. Like die scoring, rotary scoring is more accurate when the true guide and gripper are still on the sheet.
Back trimming padded book blocks | A cost-effective way to manufacture mechanically bound books is to collate, pad bind and three-knife trim book blocks in line and back trim the spine off line. When making the offline final cut, it’s important to use a double stroke that first removes the glue and then evens up the sheets.
In recent years, the shortage of quality cutter operators has fueled cutting technology workflow improvements. Binderies need to maximize operator productivity to remain competitive. Dual cutting systems are a must for high-volume postpress operations. Unfortunately, they are also expensive. Specialties Bindery installed a dual Polar cutting system capable of cutting up to a 61 x 80-inch sheet. It has all the extras, including automatic off-loaders and a paper waste-removal system. On some jobs, we’ve eliminated as many as five production people while simultaneously increasing output. For us, it has already been a very good investment.