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Saddle Stitcher Mis-Register - an Insurance Policy

[fa icon="calendar"] Fri, Apr 08, 2011 / by Andre Palko

saddle stitcher tipSeveral recent blog articles highlighted popular troubleshooting and setup techniques aimed at keeping signatures perfectly registered to the head as they travel the length of the saddle stitching machine. The tactic we're covering today is part of our series on the battle for register and it’s a simple one. In some ways it's really more of an insurance policy against mis-register. You won’t always need it but it’s a lifesaver when you have it to draw on!

When you are stitching 4 or 8pp signatures along with 16pp signatures a problem can arise due to the perf at the head of the 16 pager. In theory this shouldn’t happen, but it can if you have the right (or perhaps I should say wrong!) combination of paper stock, perf wheel and internal crossovers in the 16pp section. Everything will line up perfectly in the 16pp yet the 4pp, though trimmed exactly on the marks, simply doesn’t line up. The reason for this is the perf which can, for instance, add 1/64” or more to the head on the 16, throwing crossover register out of whack. It doesn’t sound like much but it’s clearly visible if you have a thin line crossing over.

The first suggestion is to start folding the 16’s before you cut and fold the 4’s and the cover. Most of us probably do it in this order anyway. The insurance policy is this—when laying out the job for printing, simply allow for extra head trim on all your 4’s if space is available. If you normally lay the signatures out with 1/8” head trim, then add another 1/16 or 1/8” to the 4’s. You may rarely need it but if one day you need an extra 1/32” at the head it’s there to be had. You have to cut them all anyway. Be sure to do the same for your covers.

Placement of the 4pp sigs can also make a difference in register. Once you learn your particular machine you may find that the 4’s and 8’s run better when in the middle of the stitched book, sandwiched between the 16’s on the outside and inside. For instance a 36pp self cover might run best as a 16-4-16 rather than a 4-16-16. Or your stitcher could be the exact opposite.

In theory none of this should matter and with time we can usually get any configuration to run the way we want it to. But in the real world of deadlines if a simple layout change can save us 30 minutes of setup every time we do that particular job, and it's a simple matter of putting the 4 (or 6pp or 8pp) in a specific spot, we’re going with it!

You can also experiment with various perfs at the head and you may find one that eliminates the problem on that stock. Remember however that your perf needs to be large enough to release all the air in subsequent folds, but not so large that the signature will fall apart at the perf or start to “roll” around the perf. Don’t assume that a finer perf is going to do the job either; test it. Too fine and you’ll start getting wrinkles at the head. Perf performance will change with paper densities and grain direction.

There is always a learning curve dependent on the type of stitched books you are producing on your bindery equipment. If you keep track of the problems early on, and adjust your print layouts and folding techniques accordingly, you’ll always have an extra layer of protection against the inevitable bindery gremlins.

We welcome your comments and suggestions below!

Andre Palko

Written by Andre Palko

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