To provide an offset printing machine which can easily and accurately detect a defect in a roller nip width.
The offset printing machine 10 includes: ink film thickness measuring devices 31, 32, 33, 34, 35 provided adjacent to respective measurement rollers 11, 13, 14, 15, 16; and a judgement device 36. The ink film thickness measurement devices 31, 32, 33, 34, 35 are comprised respectively of pairs of ink film thickness measuring parts 31a and 31b, 32a and 32b, 33a and 33b, 34a and 34b, and 35a and 35b. The judgment device 36 determines whether there is any nonuniformity in the nip width up to the measurement roller 13 based on signals from the ink film thickness measuring parts 32a and 32b, and if decided there is no nonuniformity, it determines whether there is any nonuniformity from the measurement roller 13 up to the measurement roller 14 from signals of the ink film thickness measuring parts 33a and 33b.
Hiroyuki Nagai
Junpei Okada
Hirohito Katsunuma
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