The life of a folding machine operator can be exasperating. It is perhaps the most stressful jobs in the printing trade. 

The complexities of how the paper is folded are not difficult but to produce the best and most accurate folding is very difficult. To achieve maximum productivity without sacrificing the accuracy is a humongous task.

Patience is the most important qualification of a good folding machine operator. The operator should have an in-depth understanding of paper, print and the folding machine.

The grain of the paper, imposition, climatic conditions, and machine settings – the list of topics that the operator should master is a lengthy one.

If one writes an instruction handbook for the folding machine operator, it will be much of a tome as an operating + spare parts machine-manual. Today’s folding machines try to provide tools to simplify settings and operations on the folding units, feeder, delivery. Sometimes it includes an electronic control module which ensures the operator can control quality and manage the job.

The BASIC RULE in folding is NEVER let your adjustments on the machine be adjustments which originate out of a frustration! If you set an adjustment and it doesn’t work then return to the original settings. Too many operators “play” with the settings and then get lost in the maze of settings (and re-settings).

During my fifty two years of experience in bookbinding, (which began in 1957 as an apprentice bookbinder for six years) I learnt hand booking and also operated many different binding machines but finally stuck with the folding machine.  Then as an instructor and then as an application specialist for MBO, I have come across instances where a folding job was ruined due to the incompetency of the operator. I do not blame them, as they are supposed to master an entire range of technicalities (like parallel folds, right-angle folds, combination folds) that can come with training and experience.

When I address my dear printer-binder friends, I ask them to give as much importance to the selection of the operator as they would give for the selection of the machine. Before handing over a machine to the operator, they should ask questions on paper, impositions, machine adjustments and so on. If they do not know the answers – please train them. I am sure your machine supplier can assist you in the process.

We can address this either by looking at a problem and tracing the source or by starting from basics. In the past few months, Welbound Times has published tech-articles on paper in relation to binding and most of the basics are common. An experienced folding operator investigates a folding problem like a detective and finds the source. He will try and examine things from the point of paper, grain, the weather, speed of the machine, roller settings and isolate the issue.

Many of the fault finding traits come with knowledge and habit. Let me try and understand a few basics through a Q&A format.

While folding, why is that long grain for thinner paper and short grain for thicker paper are preferred for accurate folding?

This has no relation to the folding requirement for a book – wherein the direction has to be parallel to the spine. What I’m trying to highlight is a problem that happens either in the case of too thin or too thick sheets. When we run the machine at maximum speeds, we notice variations. Why? What goes wrong? 

Buckled sheet
Sheet collapsing in a buckle plate

During the folding process the paper needs to be as rigid as possible. This is particularly with the first folds so that the sheet does not collapse in the fold or buckle plates. In case of thick paper, the grain should be such that it bends or buckles easily necessitating the need for short grain. On the other hand, with thin paper, the sheet will collapse with the minimum of frictional contact with upper and lower inner plate rails in the fold plates. Long grains would help prevent this. Sometimes the format of the signature demanded short grain (for the grain to be parallel to spine). I used to overcome this problem by hand creasing very lightly the leading edge of the sheets each time I loaded the feeder. Not too much as to put a permanent crease after folding but just enough to add some stability for first folds. So before you go and start adjusting the rollers or any part of the machine, please check the grain.

Why does coated paper crack during the folding process? What can you do to prevent this?

This is another issue created and associated with grain and dry paper.  Paper needs moisture to fold without “breakage” or “cracking”. Another reason is, when the layout team try to produce maximum number of pages on a sheet of paper. Now you have a problem of too many folds being squeezed and under pressure between the folding rollers. This is worse with coated text of 80lb-100lb.  If you think that it may be  a problem then cut the impositions to 2 x 16 pages instead of a single 32 page imposition.  There is too much bulk and excessive push out.  Once, I remember my stack of paper was so badly curled,  I told the paper merchant to stock it in a very damp environment.  After a couple of hours of absorbing moisture it helped to de-curl the job. It was now possible to run with less problems.

Why do we need to adjust the back plate/ lip of buckle plate?

The back plate has an adjustment to make sure the leading edge of the sheet enters the fold/buckle plate without "ducking" the mouth of the plate.  Normally, for thin papers, the back lip is brought inward toward the fold rollers. It assists easy entry of sheet in to the fold plate. This setting, however will not work with heavy weight paper. Here the sheet will enter the plate but the exiting is restricted - as the lip is too far down into the fold rollers. This will cause paper jam, bad slitting/cutting, crooked perforating with most of your accessories.

Back lip-pan

The hexagon adjustment (picture A) is for moving the back lip either in or out. Towards or away from the rollers (picture C). This adjustment deflects/catches the sheet to make sure it enters into the fold plate and doesn't “duck” the plate. Normally this adjustment is used if the leading edge of the sheet has a bad up or down curl or the paper is extremely thin, 25lb - 40lb. This also depends on the plate being used, up #1 or down #2.

Picture B shows the + and - on the side of the fold plate. The BLACK or RED mark is for reference on the back lip position. The O mark on the scale is the central position. Counter clockwise takes the lip in toward the + sign and clockwise takes it out toward the - sign.

When do I adjust the gap between the buckle plates?

We will need to make this adjustment to go well with the stability of the paper (This varies with different paper thickness).  Older type of folding machines never had this adjustment. What happens to the sheet when it enters the plate and hits the sheet stop? In a fraction of a second the sheet buckles (hence the name buckle folder), corrugates and many ripples are forced along the sheet from side to side.   Now if the gap between the buckle plates is more, then these ripples will lead to variations in fold. So what is the right gap? :  The gap should be not small so as to hinder the entry of the sheet into buckles; but just enough to keep the buckling problem to a minimum.

You do not have to make this adjustment on every set up!  If you are getting variation then this will be another area to look at.

Why have I got plastic and steel marbles for my side guide?

This one is quite simple.  Either for HEAVY or LIGHT stock.   With the heavier paper you must have control of the sheet to make sure it enters into the side guide and stays there until it gets to the first roller. If the weight within the side guide marble rail is too light, then the paper will not register. Having said that, there are many other variables like grain direction, requirement of speed etc that will decide the flow of sheets through the alignment table into the buckles. Hence some trial and error is involved here. 

If the press room have some set up sheets of the job then test your set up with this.  This way you are not taking good sheets from the actual run.

When do I skew the side guide and why do I need to?

Many a times you may get sheets with the print-area not aligned to the paper. This is mostly due to cross cut papers - either bought cheap 'stock lot' or cut incorrectly.

If the sheet is folding "out of square" constantly then this is the first area for you to check.

Fold one sheet and check it straight from the first fold.  Lay it on a flat surface and palm the sheet until all the air is out and sheet is as flat as possible. Now check the leading edge side guide corner to see if the sheet is folded edge to edge!  The way to compensate this is: a slight adjustment on the side guide. You may have to combine this with your fold plate's skew adjustment.  Try your side guide first; if it's not giving the desired result, then combine it with your fold plate.  

The corner to corner registration is checked usually in such cases where you suspect the paper to be cross-cut. Otherwise registration to be checked with folding marks.

Look forward to answering real time issues in folding, faced by WT readers. I will try my best to answer these.   

Dave Trutzenbach is the CEO of, an online site which is a hub for ordering folding machine parts. He has 52 years experience in the industry and has worked as operator of folders, managed bookbinding units, besides imparting tips about bookbinding before his retirement from MBO.

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