Possibilities and limitations of automatic presett

Possibility and limitation of automatic presetting of ink supply device (2)

there is a phenomenon in printing, that is, the size of the point on the substrate is larger than that on the printing plate. This phenomenon is called point increase, which can be clearly shown by the printing characteristic curve in Figure 3

through the known print characteristic curve, if the test equipment not only does integrated measurement, the point increase can be considered. However, at present, it is impossible to distinguish whether the tested printing area is half field, half non graphic, or eye tone. The system regards 50% flat as 50% area coverage, but contrary to the first assumption - 50/50 field/non graphic, the point increase is not considered, resulting in errors

error sources from digital database values

there are many methods to generate preset data in modern times, but they are not completely error free. When the plate scanner is not used, the measurement and plate surface error is no longer an element, but there are still errors. The image carrier still needs to use CTF self-made toys and teaching aids "ILM, and the exposure system in the film maker will also be limited by the error that may be caused by aging. Therefore, there are differences between the database and the exposed color separations, and between the exposed color separations and the printing plates made with this color separations. Although the ctplate system cancels the intermediate medium step, it is still affected by the above errors in the plate making process and the increase of printing points. The increase of points on the printed sheet can only occur when the data distribution is sufficiently detailed and the point area and field area can be distinguished. In principle, usable and more accurate preset values can be correctly obtained by using CIP3

what should be inspected when using the calibrated ink supply

when using the calibrated ink supply, the basic printing colors (yellow, magenta, cyan, black) and special colors must be distinguished. For printing basic colors, common standards have been defined before, such as Fogra. However, many printing plants have developed their own standards, which can match colors if necessary, and deviate from common standards

in order to reduce uncertainty, useful recommendations for many years are now strictly applied to the production process

the calibrated ink volume of special color ink is usually the color value (such as lab). Such requirements are usually pointed out by print buyers. Measuring from the sample can also produce correct results, but this requires that the color management system can correctly compensate for any differences in the production of the sample

the calibration density value of most special colors is not known yet, and high-end has naturally become the key goal of the future development of the film blowing machine industry, which is generally not known. Even measuring the density of the sample may produce incorrect results due to physical effects (conditional color matching)

therefore, it seems that color measurement is better than density measurement

the relationship between the calibration value and the ink film thickness

the quality of calibration inking is closely related to the relationship between the calibration value on the substrate and the ink film thickness. The quality of the substrate (paper) plays a decisive role. Even though the relationship between the density of the basic color printed on a certain grade of paper and the thickness of the ink film is very clear, we should consider that the paper actually used in production is biased. Due to the change of substrate characteristics, determining the calibrated color value has obvious advantages over the density value. Because the density measurement channel matches the basic printing color in the measurement process, the relationship between density and ink film thickness is clear on at least some papers. However, when using color values, the uncertainty is still large

how to minimize the uncertainty

the only remedy is to strictly standardize or use the printability instrument to measure the characteristic curve

for special colors, the only way is to make a rough evaluation if the printer is not used or the ink supplier does not provide relevant data. In this case, the nature of the pigment and substrate of the ink plays a decisive role

variables that affect the ink to realize the plastic lining measurement of PVC or TPE materials

on the one hand, what is the relationship between the area coverage of the image and the thickness of the ink film on the substrate? On the other hand, what is the relationship between the area coverage of the image and the adjustment value of the ink metering element

this is the performance tested by the printing machine manufacturer. Printing machine manufacturers must know what adjustment values are set for the metering elements, what area coverage is, and what is the thickness of the ink film transferred to the blanket and substrate

this is mainly determined by the actual adjustment of ink metering elements. Manroland also considered other variables:

first, the influence of the horizontal ink string of the ink supply device. The amount of ink entering the ink roller causes a part of the ink from an ink spoon to the adjacent ink spoon due to the horizontal ink string. This phenomenon can be calculated and compensated

secondly, when some ink spoons are closed, the ink flow of the ink bucket. In the past, this phenomenon was not noticed, but at that time, presupposition had a great impact. It is very important that the relevant ink spoon is accurately adjusted and turned off, otherwise this method will not work

consider other important variables

including the adjustment of the printing press. The adjustment of ink roller and water roller has a great impact on inking. Regularly checking the ink supply device according to the manufacturer's technical indicators is very important to obtain accurate ink preset results

the feeding of bucket liquid also has a considerable impact on the transfer of ink. The printing personnel should have experience and technology to ensure that the fountain solution is sufficient and not too much

finally, external influences also affect the results - especially climate. This refers to the humidity of the printing workshop and the temperature and humidity of each printing machine. Every printer knows that with the same ink supply, the printing result of the "cold" printer on Monday morning is different from that of the last shift on Friday evening. In order to avoid this problem, the only way is to air-condition the production area and install a temperature control system on the printing machine, so as to obtain stable production conditions

possible deviations

for all the mentioned influencing factors, we can estimate the possible deviations in daily production in a completely normal printing factory. The percentage rates given in the table "variables affecting the default of the automatic ink supply device" are used as a guide. In a bad environment, or when the relationship is not known, the preset result when the ink density exceeds the target value must be considered. The values in the table are only a general guideline for everyone to discuss, but □ they can provide references on which aspects they may find major problems

summary

the precondition for achieving the best preset effect is the standardized parameter of the input value. Since there has been a standard for the basic color of printing for a long time, the calculation system can use these known parameters to deduce the appropriate adjustment amount of ink spoon required for the required ink film thickness on the substrate

however, for users, the basic requirement is printing standardization, and even more importantly, prepress standardization. This is because the computing system can only work with standard programs

equally important is a good color management system, regular maintenance, calibration and adjustment of all equipment, and stable production conditions

if all these factors are appropriate, the preset automatic ink supply device will greatly save work preparation time and materials - although the matching of special colors still requires more time and investment. At the same time, these possible savings can be improved by using CIP3 to obtain preset data, so processing and measurement errors are minimized