Sounds a lot like Prinergy though Prinergy's is still called Web Growth Compensation. Though the user asking about this is not using the Kodak or Heidelberg workflow so it does them no good.
Just for clarity's sake I think marktonk was referring to sheetfed - not web. Web growth is a very different issue vs what the op described (back sheet flare).
The web growth feature lets the Prinergy software digitally compensate for press distortion.
On a web press, the main direction of growth is across the web. On a sheetfed press or flexo press, you may find more significant growth in the direction of paper travel. The web growth compensation mechanism in Prinergy can simultaneously compensate for growth across and along the web or sheet.
You can compensate for linear, non-linear, and trapezoidal or pillow-shaped scaling:
- Linear scaling–the expansion of the paper as a percentage is the same all across the paper. The percentage growth on the left side is the same in the center as on the right side. As a result, you need to convert your measurements to a percentage expansion in the x (across-web) and y (along-web) directions. See Example: web growth profile.
- Non-linear scaling–the paper expands by varying amounts across and along the paper. For more information, see Example: non-linear web growth profiles.
- Trapezoidal or pillow-shaped scaling–the expansion of the paper fans out in a trapezoidal or pillow shape. For more information, see Example: trapezoidal/pillow sheet growth profile.
Sounds a lot like Prinergy though Prinergy's is still called Web Growth Compensation. Though the user asking about this is not using the Kodak or Heidelberg workflow so it does them no good.
Hi Joe,
Our Paper Stretch Compensation works with Prinect but also can work with 1 bit tiffs so any workflow that generates a 1 bit tiff can use it.
Best,
Mark Tonkovich
Heidelberg USA
Hi Joe,
Our Paper Stretch Compensation works with Prinect but also can work with 1 bit tiffs so any workflow that generates a 1 bit tiff can use it.
Best,
Mark Tonkovich
Heidelberg USA
If you're working with 1 bit tiff (which I assume means it's been screened) wouldn't that cause issues with rosettes and moiré if the applied distortion isn't the same for all four screens?
Hi Gordon, the sizing is based on the target registration based on several tests. This actually brings the final results into registration. The paper stretch causes the rosette to go out and we are carefully stretching it back in based on the 9 areas that were used for setting up the baseline. On the sheets that I looked at, the results are in register versus being out.
I've always heard of this being referred to as sheet flare - the sheet flares at the tail after the first (black) unit's hit, resulting in the remaing three colors appearing to print 'inside', or shorter than the black image's crop lines. The problem usually shows up when running light weight and/or wrong grain stocks.
When this occurs, it's surprisingly consistent and even predictable from sheet to sheet throughout the run. The only practical solution on press is to try and shrink the black unit's image (via the split tail clamp), being careful not to crease the plate when doing so. (I know, I know, good luck with that)
I've actually seen this work to some degree but if you think it sounds ridiculous, imagine instead trying to accurately chase the flared black image by 'stretching' the cyan, magenta, and yellow plates.
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