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Figuring Spoilage And Maximizing Yields In The Bindery

In today’s marketplace, graphic arts companies must make a profit and remain price competitive.  Good spoilage planning helps companies do both.  Every significant printing job will incur some spoilage.  Since spoilage rates aren’t consistent, it’s impossible to predict exactly how many sheets will be wasted during any given production run.  (Please note: This column doesn’t contain many spoilage “rules of thumb.”  Hopefully the reason for omission will be obvious.)

Many things cause bindery spoilage.  Paper characteristics such as thickness, curl, brittleness, grade and coatings are very important.  In general, thin sheets are more easily damaged than thicker ones.  For example, when planning saddle stitched jobs, 4-page signatures should be given twice the spoilage allowance of 16-pagers, if the paper is the same weight.  Exposure to too much heat can make paper and ink brittle, resulting in excessive cracking and increased spoilage.  As the job runs, accumulating press powder and varnish buildup will gradually change the grip of the fold rollers, changing the fold position.  Humidity will make paper limp, but excessive dryness can cause static.  Either condition might hinder sheets from moving squarely into plate sections – again increasing spoilage.

Common Causes of Bindery Spoilage
Varnish.  Varnish is one of the bindery’s worst enemies and best friends.  On the one hand, it generally doubles the amount of spoilage during folding, but on the other, it certainly reduces marking problems.  Varnish buildup changes the coefficient of friction of the fold rollers.  Inexperienced operators tend to change fold settings instead of cleaning the rollers.  In most cases, cleaning will cause the fold position to return to its original setting.

Shipping.  A lot of “bindery” spoilage occurs during transportation from the pressroom to the bindery.  When shipping printed material between facilities, some damage is inevitable.  Not surprisingly, the amount of damage is directly proportionate to the care given during shipping preparation and the skill levels of those involved.  Sometimes packing choices comes down to the lesser of two evils.  Applied improperly, banding wire can cut into and damage sheets.  Stretch wrapping without corner boards will bend corners of the sheets, causing downstream machine-feeding problems.  The key to minimizing transit damage is carefully and tightly containing product so it won’t vibrate during transit or slip off the pallet.

Wood pallets and tops.  Many wood pallets and tops are made from new, or  “green,” wood with very high moisture content.   Without a barrier, moisture will migrate from the wood to the paper.  This moisture migration can destroy up to ½-inch of otherwise perfectly good printed material.

Improper over&over folding layouts.  When converting over&over folds (a.k.a. roll or barrel folds), avoid two common traps.  Paper’s third dimension – thickness – dictates that over&over folds require subsequently smaller panels.  Each succeeding fold should be 3/32” smaller than the adjacent outer panel.  However, if the differential becomes more than 3/16”, the buckle folding process will create what is commonly known as “bend-overs” on the prior fold.

Right angle folds.  Spoilage on folders increases as the number of right angle folds increase.  Each directional change gives paper another opportunity to misalign along a side guide or have a corner caught.  Once a jam occurs, sheets continue to pile up behind the jam until the operator stops the machine, wasting a lot of paper.

Recycled paper.  Recycled paper is difficult to work with.  The fibers in recycled sheets are inconsistent and short, causing a host of problems including frequent machine jamming.  Saddle stitching production rates usually aren’t adversely affected by recycled stock, but operators must constantly check that the backbone is strong enough to firmly hold the stitches.  When folding recycled paper at right angles, special attention should be given to score depth.  If these scores are too deep, the paper will split.  If it’s too shallow, the fold won’t occur in the intended position, resulting in “dog-ears.”  Since the nature of recycled fiber paper is so inconsistent, operators must effectively deal with the frustrating fact that the same score setting on two different sheets may result in split paper on the one hand and dog-ears on the other.  When allowing for folding spoilage, plan on wasting twice as many sheets whenever recycled stock is involved.

Mixing Paper Stock
Mixing brands, grades or even different lots of the same paper will increase spoilage.  If a pressman runs out of stock and substitutes a similar sheet, expect different performance levels in the bindery.  Paper lot changes should be clearly marked on skids and kept separate as the job transfers between departments.  For example, if a cutting operator finishes cutting a job and mixes different papers without identifying which is which, a folding operator will have no idea why a fold position suddenly moved and why the crossover, which was perfect ten sheets ago, is now 1/8” out of alignment.  If the operator doesn’t waste a lot a sheets making the necessary adjustments, a lot of time will be wasted – or very likely both.  Even worse, if an unmarked skid from the first lot remains, the machine will have to be adjusted back to the original settings.  In general, whenever different stock is used on a job, plan for 1½-percent additional spoilage allowance.

To Cut Or Not To Cut?
Sometimes printers ask who should do the cutting: the bindery or themselves?  In general, yields will be higher if the bindery cuts the product to final size.  Whenever work in process is packed and shipped, some sheets will have damaged corners, curls and little rips.  If your bindery cuts the product after shipping, a lot of damage can be trimmed off during the final cuts, eliminating a lot of “bindery” spoilage.

Personalized Products
Personalized jobs requiring 100% successful bindery conversion present special spoilage problems.  Let’s assume you have a 10,000-piece personalized job and the bindery successfully converts 9,800 of them.  From the saved waste, a list of the unsuccessful 200 names can be regenerated.  Then, three consecutive lots of the destroyed pieces should be re-personalized so every record has three chances of being properly converted.  During the second run of 600 pieces (200 x 3), it is highly unlikely that the exact same sequentially positioned documents would be spoiled on three successive passes, thus making “100% mailings” manageable.

Overs/Unders
Most print customers will accept some flexibility in final count because they understand that graphic arts production has many variables.  Industry standards allow ten percent over runs and under runs for most jobs.  As the following example illustrates, it is to your customers’ economic benefit to accept the industry standard of 10% overs and unders.

If a customer orders 100,000 pieces and won’t allow any “unders,” prudent estimators will plan to net 110,000 good pieces to eliminate the risk of going back to press at their own expense in the event of an “under” situation.  Every manufacturing stage at which spoilage is expected should have reasonable expectations of product loss assigned.  This 100,000-piece job with no allowed unders will be priced at 110,000 pieces – inflating the price 10%.  This begs the question: Why not just order 110,000 pieces and get an additional 10,000 pieces at no additional charge?  (Hint: you should.)

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How can spoilage rates be confidently predicted when it’s well known that the same job run twenty times, will have twenty different yields?  In short, there is no substitute for bindery experience and technical competence.  At Rickard Bindery, we have developed general spoilage guidelines, but we recognize that every job needs to be carefully analyzed for potential or unusual spoilage exposure.

Kevin Rickard is Vice President of Operations for Rickard Bindery and a Director of the Binding Industries of America.  Rickard Bindery specializes in discovering solutions to challenging folding, saddle stitching, gluing and other bindery jobs.  Kevin can be reached at (800) 747-1389.