Need Help Understanding Unintentionally Shrinking Images

[kslight]

Hi I found one other thread similar to this but it didn't appear to get resolved so I hope I am not posting something that's already been answered...if it has, please pass the link on!


When we print files to any of our machines the image shrinks *slightly*. For example...if we setup a business card 3.5x2 24-up on 11x17 (no bleed) the crops actually measure
3.5x1.98-ish, and from there they are all stepped the same size. All files sent to the floor are imposed in Acrobat/Quite Imposing, and that is where the crops are being created as well. We do not have auto-fit to page, auto-rotate, or anything like that enabled that I'm aware of (any other suggestions on what should be checked/unchecked would be helpful). This problem is not machine or file exclusive, I can send files to our 2045 and 2060 with Fiery RIP, or 6060 with Creo RIP, or 6180s with DocuSP.... This leads me to believe that it is not a machine issue (all measurements are off exactly the same across all machines), just something odd happening in our graphics PCs?

This is also not a new issue for us, just one that I've been asked to revisit to see if there is a legitimate reason this should be happening or if we are doing something wrong. I have worked other places that use similar Xerox equipment and don't recall ever running into this problem as a cutter operator...I remember being able to cut most cards at 3.5x2 exactly without issues.

Any ideas?

 

[kyle]

Try rotating the image 90 degrees in different places, like in the PDF document supplied to the RIP, then in the RIP, etc. to see when the axis that shrinks changes. Could is simply be the paper shrinking from the heat of the machine? Try printing the same thing on a light stock then a heavy stock and compare, and/or try running stock through without imaging first (print a blank page), then again with the image to see if the dimensions are the same as when it runs through only once. The alignment of one axis is likely dependent upon the machine accurately matching the speed of the paper (or more likely a drum/belt) with the rate the image is laid down. If that's the issue, you probably wouldn't see exactly the same result on different printers, however.

 

[kslight]

Try rotating the image 90 degrees in different places, like in the PDF document supplied to the RIP, then in the RIP, etc. to see when the axis that shrinks changes. Could is simply be the paper shrinking from the heat of the machine? Try printing the same thing on a light stock then a heavy stock and compare, and/or try running stock through without imaging first (print a blank page), then again with the image to see if the dimensions are the same as when it runs through only once. The alignment of one axis is likely dependent upon the machine accurately matching the speed of the paper (or more likely a drum/belt) with the rate the image is laid down. If that's the issue, you probably wouldn't see exactly the same result on different printers, however.

1. That sounds like a good idea, I'll try that, though I think I've narrowed it down to a graphics issue, because the problem is identical on all machines. At the RIP level I can only rotate by 180 degrees however. I find it odd that the long edge of business cards stay at 3.5", but the 2" edge becomes shorter (the job is setup 3 rows of 8 columns, fed short edge first 11x17).

2. I wouldn't think so? The specific job that we are using as an example is a business card, which runs on 100# Cougar cover, and I also tried it on lighter weights with the same results. The size does stay consistent across the run. I would think that if the paper were shrinking then it would be different across the different machines...because I think they all fuse at different temperatures.




Anyone else have any ideas?

 

[kslight]

*bump* Still need advice on this.

 

[Joe]

It seems this has to almost certainly be paper shrinkage. One way to test this is if your RIP has a viewer so you can measure the ripped file and see if it has changed before going into the printer. I would be surprised if it has changed.

A solution, if it is consistant, is to scale the file a small amount (like 100.01%. ( 2" / 1.98" = 1.01010101010101")) in the one dimension that is changing. It would be similar to web growth compensation for the individual separations on a web press only this would just be compensation on the composite file.