Explain the progress of ink transfer research by sheetfed offset press (two)
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In order to get accurate values from the simulation as much as possible, it is necessary to consider all the influencing factors in the simulation model. To ensure this, it is necessary to do a lot of work to validate the simulation tools and adapt the simulation tools.
Jiang proposed a different simulation model. In the model, the ink transfer system is considered to be a transfer system under control, where the supply of ink represents the input signal and the ink transferred to the photosensitive layer acts as an output signal. The split signal is the input of intermittent ink, ie plate cylinder gap and single print image. The complete ink transfer function of the ink transfer system consists of an independent transfer function for each pair of ink rollers. The simulation is performed in the frequency domain, and ink transfer is used as a hysteresis factor. Due to time variations and non-linearities, it is quite difficult to record the ink transferred to the plate and can only be calculated by simplified linearization.
When changing the supply of ink, the first model calculates the results of the response of the ink delivery system to time. In the transverse direction, optimization of the average thickness of the ink layer is impossible.
Experimental study on ink transfer
The regularity of ink transfer plays a very important role in the design of ink transfer systems and wetting systems. Experimental research in this field began in the early days. Broetz and Hars obtained recent experimental findings in two FGD research projects. In other studies, one of the goals of these research projects was to determine the specific amount of ink split for the simulation program established by Patzelt and Ruder.
Experiments and independent studies of all relevant variables that have an effect on the amount of ink splitting have established a complex set of experimental footholds. It includes a continuous ink transfer system with a cantilever bearing driven ink roller, ink temperature control, printing equipment (plate and impression cylinder) and unwinding and rewinding equipment.
The measurement of the thickness of the ink layer is extremely important and must be non-contact. In addition to the traditional instrument for measuring ink thickness, a mechanism-built measurement system consistent with it is used to measure the thickness of the ink layer. The ink layer thickness measuring instrument invented by FOGRA uses infrared rays because the maximum absorption value of the wetting liquid and the ink overlap in the maximum range is expressed in this band. The signal is completely separated due to the overlapping absorption spectrum of the wetting fluid and ink in the widest range. Absolute measurement of the thickness of the wetting fluid and ink layer is only possible with a precise scale. Since the measurement of the ink layer thickness gauge is only possible on the plate material, an additional roller is required to measure the thickness of the ink layer on the elastic ink roller. This has led to the development of the above-mentioned ink layer thickness sensor. The sensor uses visible light, but can only be used without dampening fluid. These two tests
The calibration system requires calibration in order to determine the thickness of the ink layer by measurement.
All ink layer splitting factors. Or a different ink layer splitting factor β is used as a parameter describing the ink transfer consistent with the following equation:
Aij=s‘j/(si+sj)
=s‘j/(s‘i+s‘j)
Ijij=(sj+sj)/(si-sj)
=(si- si‘)/(si-sj)
=W/(si- sj)
(aij is the total ink layer splitting factor, s is the ink layer thickness, βij is the difference of the ink layer splitting factor, and w is the thickness of the ink layer that is transferred)
The determination of most of the variable parameters requires experimentation, and it is more difficult to clearly and comprehensively describe the results of the parameters. Thus, the experiment and description are carried out with one parameter changing while the other parameters are unchanged.
Tests have shown that there is an interdependence between ink splitting factors at the ink separation wobble frequency at constant printing speeds. In the case of experimentally input dampening fluid, the ink splitting factor was recognized to be faster than in the absence of input dampening fluid.
Conclusion
The large number of parameters and methods described in the designed experiments are now being used more and more. Increasing the importance of these parameters and methods through multivariate changes allows for a reduction in the number of experiments, that is, in each experiment, several variable parameters are changed. The ink layer thickness measuring instrument invented by FOGRA is a more advanced instrument in the world, and has practical value for measuring the transfer of ink.
Experiments to date have led to significant improvements in the level of awareness of dampening fluids and ink transfer. However, a complete description of a set of formulas takes into account all relevant parameters, and this description is still not found.