We are a running a 6-unit heatset half-web press. We completed the G7 qualification in February of this year. For approximately 6-weeks after the qualification, we were able to match proofs by running at the target solid ink densities we established during the G7 process. We had very low make-ready waste during this time and the pressmen were able to set the density targets in the closed-loop color system and know that the color would match the proof.
At some point, we began to drift from the density targets we established with the G7 curves. It is evident in both conventional and FM work.
[Nailing down the exact point in time has been difficult because we ran several film based jobs and jobs on uncoated papers around the time this issue started. 98% of our work is done at 175 LS on gloss or dull paper.]
Looking at the data, the variance is in the Black, Magenta, and Yellow. The Cyan is printing right where it is expected to print.
Targets
Density Dot Gain
K 1.63 23-25
C 1.35 16-19
M 1.30 18-21
Y 0.92 17-20
Actual (Average density across the sheet from 40+ jobs)
Density Dot Gain
K 1.56 28.3
C 1.36 17.9
M 1.20 23.1
Y 0.90 25.3
My theory is that there is excessive dot gain in the K, M, & Y. In order to keep the gray balance and match proofs, the pressmen are reducing the density targets. This provides us with acceptable color, but I am losing the efficiencies of having a calibrated press that runs at consistent density to match proofs.
I am looking for potential root causes of this problem and I would like your help.
I am inclined to believe the problems lies in the pressroom rather than Pre-Press. My ink is the most likely suspect and I am working with my vendor to analyze the ink.
Do you suspect there could be anything in pre-press that could cause this type of problem? If it were in all the colors, I would think a pre-press issue would be a more likely cause.
I do not believe it is blankets, fountain solution, packing, roller settings or temperatures as these items have been changed or are common to all printing units. We have run the inks in different units and have had the same results.
Any help would be greatly appreciated.
Thanks,
Brian
At some point, we began to drift from the density targets we established with the G7 curves. It is evident in both conventional and FM work.
[Nailing down the exact point in time has been difficult because we ran several film based jobs and jobs on uncoated papers around the time this issue started. 98% of our work is done at 175 LS on gloss or dull paper.]
Looking at the data, the variance is in the Black, Magenta, and Yellow. The Cyan is printing right where it is expected to print.
Targets
Density Dot Gain
K 1.63 23-25
C 1.35 16-19
M 1.30 18-21
Y 0.92 17-20
Actual (Average density across the sheet from 40+ jobs)
Density Dot Gain
K 1.56 28.3
C 1.36 17.9
M 1.20 23.1
Y 0.90 25.3
My theory is that there is excessive dot gain in the K, M, & Y. In order to keep the gray balance and match proofs, the pressmen are reducing the density targets. This provides us with acceptable color, but I am losing the efficiencies of having a calibrated press that runs at consistent density to match proofs.
I am looking for potential root causes of this problem and I would like your help.
I am inclined to believe the problems lies in the pressroom rather than Pre-Press. My ink is the most likely suspect and I am working with my vendor to analyze the ink.
Do you suspect there could be anything in pre-press that could cause this type of problem? If it were in all the colors, I would think a pre-press issue would be a more likely cause.
I do not believe it is blankets, fountain solution, packing, roller settings or temperatures as these items have been changed or are common to all printing units. We have run the inks in different units and have had the same results.
Any help would be greatly appreciated.
Thanks,
Brian