Digital BW, The Print

Hi,

I'm doing black only printing and I get very subtile banding in the 
printing direction, not in the direction the printerhead is moving.

They are not from any part of the printer that I can identify and 
they are about 1/2 cm wide. They are more obvious in the gray areas.

They are not visible when I do color printing or Duotone printing.

Any ideas?

By the way, BO printing is great. After some tweeking with dot gain 
profiles and curves I'm getting prints that are as much better than 
my Doutone prints and without the colorcasting. Just need to remove 
the banding.

Rickard.