I need some help, first off I am not a pressman but a long time prepress guy and I am trying to help my pressroom manager troubleshoot a issue on a 5 month old Mitsubishi sheet feed press. We noticed a few weeks ago that we were starting to have some issues matching our Swop calibrated proofs on press (18% dot gain built in) where as they had been beautiful before. I started pulling sheets and measuring dot gain and noticed that the whole press was falling off over the last 4 weeks.
I took a sheet that ran 4 weeks ago and the Solid Magenta was ran at 1.41 and had a dot gain of 15% which is a bit clean as it normally was about 17% and then yesterday we had a job that ran that was on the same stock same everything and now with a Solid Magenta density of 1.48 had a dot gain of 9%. This is happening across the whole press so I know it can't just be one unit that is say underpacked or has bad rollers. We know the plates that went on press were fine as we only run linear plates and we read every plate as a q.c. measure.
Any ideas where to start, could it be that the rollers were not set properly? Or need to re-reset as they are tightening up. The press is ran 24-5 so it already has a good amount of impressions but I can't believe that it would need new rollers already. Fountain solution? Conductivity?
Any ideas would be greatly appreciated.
thanks,
Dub
I took a sheet that ran 4 weeks ago and the Solid Magenta was ran at 1.41 and had a dot gain of 15% which is a bit clean as it normally was about 17% and then yesterday we had a job that ran that was on the same stock same everything and now with a Solid Magenta density of 1.48 had a dot gain of 9%. This is happening across the whole press so I know it can't just be one unit that is say underpacked or has bad rollers. We know the plates that went on press were fine as we only run linear plates and we read every plate as a q.c. measure.
Any ideas where to start, could it be that the rollers were not set properly? Or need to re-reset as they are tightening up. The press is ran 24-5 so it already has a good amount of impressions but I can't believe that it would need new rollers already. Fountain solution? Conductivity?
Any ideas would be greatly appreciated.
thanks,
Dub