| 摘要 |
PROBLEM TO BE SOLVED: To improve a printing quality on a metal plate and to maintain a stable color tone by automatically controlling change of a nip pressure caused by swelling of an offset roll whose surface is covered by a rubber. SOLUTION: A sensor 51 for detecting a nip pressure such as a load cell or the like which detects a nip pressure between a press plate roll 28 and an offset roll 29 is set to the press plate roll 28. When the offset roll 29 swells by a solvent in printing ink and, as a result, a nip pressure detected by the sensor 51 for detecting the nip pressure is increased compared with a set nip pressure, the nip pressure is controlled so as to be the set nip pressure by moving the press plate roll 28 with a motor 58 for moving installed on the side of the press plate roll 28. On the other hand, with regard to a nip pressure control of a backup roll 30, a moving amount of the press plate roll 28 by the motor 52 for moving is calculated by a computer and fed back to a motor 53 for moving of the backup roll 30, which moves the backup roll 30 against the offset roll 29, which controls a nip pressure between the backup roll 30 and the offset roll 29 so as to be a set nip pressure. |
