Image loss on a flexo sleeve print


New member
Hello Everyone!
I have a customer who is using SBR/natural rubber covered print sleeves to print water-based ink on a kraft paper. They are telling me that after about 12 hours at run speed on their Comco press, they are experiencing image loss causing them to increase the pressure on their print gear to recover it. After 24 hours of run time, the image loss and resulting increases of pressure to their gear is causing chatter in the print on the gear side of the run with successful print on the non-gear side of the print.
This is to be expected as I am assuming that the increased pressure to one side of the mandrel is causing the system to be off-kilter resulting in a lighter, KISS impression on the non-gear side.
I am also assuming (until I receive samples from the customer) that the "image loss" they are experiencing is more likely doughnuts as it manifests primarily in the fine type (4pt and smaller) areas of the print.
My question then becomes, what could be causing the doughnuts to occur prior to the increase in pressure? Is it possible that this is an ink viscosity issue? Would 12 hours of run time be enough to allow the anilox to dirty or conversely, is it equally or more likely that there is too much ink draw to begin with?
The press operator is not the most experienced and they are printing in black. Without experience to know the difference between K and rich black, would over inking to achieve a rich black look with K ink result in doughnuts in the print?
This one has me stumped.
Thanks in advance for any insight!


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