Horizontal lines printing at 720dpi

I am printing direct to photopolymer plate and get dark horizontal lines caused by slight overlap at 720dpi. They also happen on thin glossy paper taped to an old plate and testing indicates they go away at 1440dpi. Using 79-99-PiezoDN-Pos-Master in a 7900 with selenium K7. The paper thickness is set to heavyweight polyester and 32mil. Head alignment does not seem to be the problem.
Is there something I can do or should I just change resolution. I am somewhat invested in the lower print resolution.


720dpi will always give you lines with the dithers available in QuadtoneRIP sadly.

These curves and the QTR driver were built for 2880x1440 or 1440x720 minimum.

The driver I’m working on has a different set of dithers that may solve this. It will be coming out for PiezoDN in a month.


Thanks for your answer so late at night for you.


I had a similar problem when printing images set at 360ppi and printing at 720 dpi using IJM inks. The banding resolved printing at 1440dpi at 360ppi as well as at 240ppi. This was with intermittent nozzle check printout in C at the 8th line from the top. I tried multiple cleanings at all levels never resolved in the nozzle check, but when printing a CMYRGB Color target with complementary field as stated above; no banding! Printing at 1440dpi only uses about 5% more ink.

I should have said this was with my 4900. My 9900 prints like a dream.