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Making the Most of Pin Registration

(May 2003) posted on Tue Jun 03, 2003

Discover how to refine each step of the prepress workflow so you can realize the benefits of pin registration.


By Mark A. Coudray

You'll find yourself in trouble if you create new layouts for every job, or if you try to be too conservative with film use. In both cases, the results are randomly generated positives that must be dealt with on an individual basis. This lack of repeatability in your system plays a huge role in misregistration on press. Each job is new and different, which makes it challenging to spot problems in advance. As a result, mistakes flow through unnoticed and typically show up much later in the process where they are most expensive to fix.

 

Film positives

 

Film-positive generation is the next step. The ideal method would be to utilize prepunched film within a drum imagesetter. Machine tolerance determines film-to-film accuracy, and drum systems usually are accurate to ±0.0002 in. This is much, much finer than you can print, but it is stable and repeatable. Prepunched film is a huge bonus because you can use the punched holes to further guarantee extremely accurate image transfer in latter stages of the process.

 

Barring punched film, you are stuck with capstan or roll-fed film. These are the materials used with just about every imagesetting device out there, be it inkjet, thermal, toner, or laser-based. The important factors to consider are the accuracy of the image-to-image placement for separations and the flatness of the final imaged film. If film separations don't accurately line up at this stage, they will not align on the screen or on press.

 

How close an alignment is good enough depends on your preferences. For me, it is not a visual factor. I insist that separations must appear aligned when viewed under 10x magnification because accuracy degrades at each stage of the process. You must be much more critical at the front end of the process because things only get worse as you move along.

 

Film curl causes big problems. The curl creates tension within the film (and the carrier base, if you use one). This tension wants to resolve itself, which usually means something is going to move. The movement often happens during the vacuum phase as the layers of film and screen come together. The curled film wants to scoot around and can be very difficult to control.

 


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