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Thread: Roll Alignment Best Practice

  1. #1
    Associate Engineer
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    May 2017
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    Roll Alignment Best Practice

    Hi All,

    New member here to the forums and look forward to joining in on topics and learning from all of you. But to start off I do have a question regarding roll alignment best practices for film machines and tolerances recommended for roller error. We are currently using VFFS baggers that seem to have quite a bit of error which we think is leading to film tracking issues. We just recently purchased a roll alignment laser and started getting a few readings and for rolls that are about 2-3 feet away from each other seem to have about a 0.25" offset error. I can't imagine this is conducive for film tracking so we are looking to try and re-align rollers to get them to a parallel state. I just wanted to gauge what a reasonable tolerance error is for a setup like this or if the current error we are seeing is even relevant on such a small scale as this (compared to most larger film machines). Feel free to ask any questions if what I presented wasn't quite clear.

    Thanks
    Last edited by kgfoster2; 05-10-2017 at 11:55 AM.

  2. #2
    Technical Fellow jboggs's Avatar
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    I don't know what size rollers you're talking about but 1/4" tracking error in 3 feet seems pretty severe to me. I recently set up a line running a metal ribbon through a series of 8" dia rollers and process elements at fairly high speed and tension levels over 35 ft end to end. We shot for less than 1/16" error over that whole distance. But the bottom line is the product. If it runs ok, your alignment is good enough. If it doesn't, it isn't. Simple. After repeatedly inserting and removing numerous shims of varying thicknesses over and over again at each roller, I designed roller mounts that provide adjustable alignment in both horizontal and vertical axes. Saved SO much time! Just my thoughts...

  3. #3
    Associate Engineer
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    We are using about 1 1/4" rolls that are just about 4' wide. Most of our machines we have had to put in actual hard stops on the rolls on one side to stop the film from tracking up. We just aligned some of the baggers today so we'll see if that helps but we still had some rollers that were up to 1/8" off parallel. Were the roller mounts you designed like a double slotted bracket that let you go vertical and horizontal?

  4. #4
    Technical Fellow jboggs's Avatar
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    For alignment you need to change the angle of the roller axes, not their position. If I am correctly picturing what you're asking, slotted brackets would only change the rollers' position, not their angle. I built in two pivots, one horizontal and one vertical, along with a way to lock each one. You may not need that level of complexity. Maybe a few shims will take care of it. I'm surprised the rollers can be that far out. Are they all mounted on a common back surface? In our experience if your rollers are all aligned correctly (angularly) you won't need edge flanges.

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