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How to Fold Envelopes to Run on a Saddle Stitcher

[fa icon="calendar"] Fri, May 04, 2012 / by Andre Palko

If you've ever had to fold reply envelopes for inserting in a saddle stitched book, then you understand suffering.  You’ve got it all working against you:

  • envelope foldingEnvelopes are small, spongy and harder to feed than regular signatures
  • They usually have to float between stitches which is a saddle stitcher task made up of equal parts skill, art and luck
  • When floating an envelope the caliper often has to be disengaged, depending on the model of stitcher as well as size and location of envelope. That means your risk of shipping books with missing signatures is extremely high, unless your operators have the eyes of eagles and can sense a faulty trimmed book or catch dropping signatures the instant a pocket starts to misfeed.
  • Folding envelopes is notoriously difficult and can make a grown operator cry, depending on the type of folding equipment available for the job

When I was a bindery manager we ran countless stitched books with reply envelopes and it seemed that the envelope was the only thing we could never get quite right. It always bugged me. Sometimes they fold well; sometimes not. Scoring top or bottom makes no difference and can make it worse. We ran them on MBO, Stahl, Baums and even a Bobst folder gluer. Granted, if it made it to the book OK, a crooked fold didn’t make any aesthetic difference. It just had to be there, wrapped around the pages so as not to fall out of the book.

envelope jamIt was the unpredictable, inconsistent nature of the folding operation that was frustrating to both folder and stitcher operator. If it was particularly bad the lip would vary and cause lots of misses in the pocket. Or we'd get the periodic jam caused by a single poorly folded envelope that slipped past the person loading pockets. Or perhaps the fold was buckled in on one corner so the envelope wouldn’t seat properly on the signature, leading to more jam ups (drawing left.)

I had successfully blocked these memories when a Bindery Success reader recently emailed for help after an envelope job ruined his weekend. The good news is that these pesky envelopes can be folded just fine with the right equipment.

If you’re running buckle folders, the addition of a wet score will help according to several readers. One operator fine tunes his wet score solution with a 70% alcohol + 30% water mix, which is the opposite of what is normally used.  It’s his experience that the higher concentration of isopropyl alcohol prevents the gummed flaps from sticking better than the conventional solution, and the wet score line aids folding accuracy.

Some readers use various feeders inline with a buckle folder or right angle section to simplify the feeding process. It doesn’t solve the folding problem but it’s easier to feed envelopes this way than with a continuous feeder.

If you are fortunate to have a knife folding unit and a way to feed the envelopes, you should be able to get a much better folding job. With a knife unit, register control is not dependent on the fold rollers getting a consistent, even grip on the envelope but rather on the stops that position it under the knife. Some readers also use a wet score with their knife fold setup.

What do you do if you have neither a wet score nor a knife folder? Relax, grab a cup of coffee and mentally prepare yourself to experiment.

  • If you have multiple folding machines, test every machine. We often got our best results on a very old Baum retrofitted with rubber rollers.
  • Try all the fold plates and all right angle sections. One may give you a better result than the others.
  • Turn the envelope around and feed the opposite way.
  • Use a wooden block to hammer the offending skewed envelopes back into some semblance of being square. It’s a tedious but workable solution for a moderate quantity.
  • Lastly, be sure the person feeding the envelopes on the stitcher has a good eye for pulling bad ones.

These are by no means perfect solutions for running envelopes on buckle folders. But one or more of these methods could deliver a small improvement, good enough to prevent a ruined weekend!  As always, feel free to share your techniques and suggestions below.

Topics: Bindery How-To Tips, Saddle Stitchers, Folding Machines

Andre Palko

Written by Andre Palko

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