Dampers are the small filters that filter the pigments as they pass from the ink lines going to the ink carts to the print heads. Often what ends up clogging dampers is residue from cotton rag papers as well as impurities in the inks themselves.
Each ink cart has its own damper which is attached to the bottom of the print head. With piezo printers like Epson, Roland, and Mimaki, dampers are often the first mechanical thing to check when head cleanings can't solve the blocked nozzles. Dampers are cheap and fairly easy to replace and are available for just about every Epson printer that has been made. If you run a lot of cotton paper you should change them more often. Normally you take the head cover off and you can access them fairly easily.
I believe Roland recommends changing out their dampers regularly and unlike Epson, they make it very easy to accomplish.
Changing the dampers won't help you if you have defective pressurized ink carts though.
sorry, but this is rubbish.