Plate Registration

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Plate Registration

Postby Flexo Grunt » Fri Feb 26, 2010 11:31 am

We are having a debate about registration and the "grain" of the plate material. One of my coworkers has been told that using film you need to keep the negs (bearer bars) running all with the grain, or against the grain, claiming if you burn two negs with the bearers running 90° to each other you will have registration problems. I had never heard this before and my last shop ran plates using the best fit on the material regardless of direction and we never experienced fit problems. We had also used digital plates and had much tighter registration. Does this make a difference? Any thoughts?
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Re: Plate Registration

Postby exflexo » Sat Feb 27, 2010 12:35 am

In theory, you should be able to position negatives any way you want to on a flat plate and I doubt you will see much difference in registration. And if you burn up one of several colors on press, how would you know which way it positioned unless you keep track of every single negative? In all of my experience, I have never seen a registration issue caused by placing two negatives perpendicular from each other on a flat plate. If you are seeing a regisration issue, I highly doubt it is because of the "grain" of the plate... the issue is probably due to something else. The one exception to this would probably be liquid photopolymer because of the way the polymer is poured and how it moves while it is setting up. But then again, most liquid photopolymer has 1/8" traps, so even that is a moot point.

On a similar note, I have also seen registration issues on a direct to plate imager when two images were imposed perpendicular to each other. But even this issue was not caused by the polymer and was quickly resolved by calibrating the imager.

Regardless of the info above though, whenever possible, I kept images "pointing" in the same direction. I worked in a trade shop environment, and I wanted my plates to have a washed out floor that looked the same from plate to plate. All washout processors, whether Rotary, In-line, Orbital or Thermal will leave a tell-tale pattern on the floor of the plate... I was picky and liked the plates to look the same, so I kept them the same direction.
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Re: Plate Registration

Postby Flexo Grunt » Tue Mar 16, 2010 7:59 am

You are confirming what I suspected. I have been sneaking a few plates out there that are "against the grain" and I have heard no complaints. Thanks for your reply.
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Re: Plate Registration

Postby Ulah! » Fri Jul 02, 2010 10:53 am

Could it be that the length of film output by the imagesetter may be inaccurate. images output at 90 degrees to one another may then not quite fit
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Re: Plate Registration

Postby Flexo Grunt » Tue Jul 06, 2010 9:16 am

I always make sure the film is imaged in the same direction. I have learned that there have been problems with registration with plates imaged perpendicular to each other using the fast system, but I haven't had any registration complaints burning film perpendicular.
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Re: Plate Registration

Postby prepmpibaltimore » Wed Oct 20, 2010 10:12 pm

We have done the same thing in regards to sending plates out running in opposite directions of each other, and we have not heard of registration issues. We also ran test where we would run a line through the imager going different directions and found all of them measure the same. One thing we have found if you are running a DuPont Fast unit you may see registration issues once in a blue moon, and it could stem from the IR Heater spiking.
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