Details:
Summary:
This report is divided into 2 parts, the first part dealing with methods of measuring which is used today in quality evaluations of letterpress printing presses, and the instruments used for this purpose at the research laboratories of The Graphic College. The measurements include tests on stability, defections, evenness of the bed, pre- tension and tolerances of the individual elements in the printing press. Furthermore the first part of the report offers a submittance of those points of view we have taken with respect to future testing since, in our opinion, the aim must be a determination of the deformation of the individual parts in the press. The second part is a discussion about the pressures acting during the printing process, especially the influence from the cylinder-diameter. Based on theoretical considerations concerning the linear pressure-distribution a series of printing tests have been carried out. The ink transfer to baryta paper is determined as a function of 2 different pressure-distributions for different types of inks. For the tests a specially constructed strain gauge fitted pressure gauge connected to an oscillograph, a speed-meter, in connection to an oscilloscript and a weighable solid are used. The investigations show first of all that one cannot expect the same splitting constant when printing at 2 different pressure-distributions, but a more thorough acquaintance with other forces acting during the printing (such as tangential foxes) would certainly be desirable. An attempt has been carried out to detect a relationship between the ratio of the initially absorbed ink-volumes in the paper and the different conditions of printing.