The closed system consists of an inverted cup with a doctor ring. The doctor ring is made either of hard metal or ceramics. It has the task of removing excess ink from the cliché. The cup is filled with ink and simply dragged over the cliché. The advantage is that the ink is completed sealed in and needs much less maintenance. There’s practically no odor emission.
In an open system, the flood bar floods the cliché with ink from the ink cup. Then the doctor blade removes any excessive ink from the cliché. The advantage over a closed system is the small cliché surface.
Transverse doctoring unit
The transverse doctoring unit is a system for very long print images in a closed inkwell. The cup must move repeatedly over the long cliché. The print image is larger than the area the used cup can cover. To prevent the ink from drying on the cliché image, the cup moves non- stop back and forth over the cliché image.