To reduce printing paper which is lost until a color density is converged on a target color density at the start of printing, and to enhance an operating ratio of an offset printing machine, in a method for controlling an ink key of the offset printing machine.
In this method for controlling the ink key by using the color density which is obtained by measuring printed matter of the offset printing machine, the color density in an initial stationary state is predicted by using the color density which is measured within a time frame from the time of the start of the printing to the time when the color density reaches the initial stationary state; and the ink key is controlled based on a difference between the predicted color density in the initial stationary state and the preset target color density. An ink key control device realizes the method. Additionally, the color density in the initial stationary state is predicted from printing time.
MOGI MASAO
SHIMAMURA YOSHIKAZU
