These control marks enable the register of a press to be checked to within a few micrometers. Such checks may, for example, be carried out during the acceptance trials for a press.
The FNM is supplied in the form of two small films with different scales. One of these films is mounted on the copy for one press unit and the other on the copy for the next unit.
After printing, reg ister differences as small as 5 pm can be read off and the measurements are entered into the FOGRA assessment form supplied with the strips. The assessment provides a statistical value in pm that is an unambiguous measure of deviations in circumferential and sidelay register. The smaller this value (which is the register standard deviation), the better the register accuracy of the press.
The control scales are supplied with detailed instructions, including the assessment form.
