Under the control of the dot in the printing proce

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Control of points in textile printing process (Part 2)

correct measurement

when the distance from the plate reaches the maximum (high/low, low/high), some problems will also occur. The most obvious is the jump and gap caused by the ink penetrating into the clothes. Points that are not aligned with the fabric of the garment will remain behind the template. If there are more than two low-pressure printing plates forming a row, the ink will continue to accumulate behind the template with graphics and text

if this template is placed in a medium or high position in the next printing, the excess ink behind it will be superimposed twice or even three times, resulting in a certain point expansion. In the next high-level printing (minimum interval sequence), the ink will be removed and left on the clothes. The color of the printed pattern looks very light, because there is no ink stored behind the template

the whole process is called "dumping" at 12. We created a deep/shallow cycle in the printing process. Among them, the samples with poor penetration effect and incomplete penetration are the most typical. This kind of samples are printed after printing the printing materials with excessive ink penetration and dot expansion (50% or more). I recently made a trial print in a customer's factory, and the results showed that the dot enlargement value on the imprint plate with "dumping" phenomenon was higher than 70%

when we want to increase the pressure of the doctor blade to optimize (maximize) the distance between the print head and the embossing plate, so as to achieve uniform printing, the problems in production also increase. At this time, there will be a great pressure change between the print head/imprint disk with the smallest spacing, resulting in "dumping", infiltration and dot expansion

if printing is carried out on the same printing machine, the ink behind the template (not printed on the "no way to limit the output of fibers in the whole industry like coal) will reach a statistical balance through all templates. The point expansion will gradually reach a balance and become stable and predictable, so that we can manage it

in order to obtain correct statistical results, we need to determine what the real changes are. This means measuring the distance between the print head and the imprint disk on each device. Once the real amount of change is determined, we can correct the relationship between point expansion and distance. This can be used to predict the results in advance

first, all print heads and platens must be numbered sequentially. In this way, it is convenient for us to evaluate the relationship between each print head and the imprint disk by measuring and analyzing the distance between each print head and the imprint disk. The most important thing is to print the dot expansion target on the uncorrected but marked printer., In order to measure the point enlargement value related to each print head/platen combination. Next, we can measure the distance between the print head and the platen in each combination. Then, we can adjust the printing machine and the platen to a balanced state

when this process is completed, the distance between all print heads and the imprint disc will be the same, and each imprint disc and each print quality assurance period will be at the same level. We may not be able to adjust a combination of print head and platen to a horizontal or parallel state, but we can use the change of point enlargement in the initial printing to determine our expectation for point enlargement of this printer

we need a specific method to achieve the best performance. First, the platen must be horizontal and parallel to each print head. The acceptable range of variation depends on the structure of each printer and the control of the pressure of the doctor blade and the floodbar. In addition, I think the best basic starting point for the distance from the plate should be 0.06 inch

secondly, we should print enough samples to reach the balance point. No matter what the dot enlargement is, its value between the print head and the embossing disk should be consistent, with an error of no more than%. If the printer is not calibrated, the difference between each print head/platen combination may be higher than 40%, which is entirely caused by the pressure and distance changes of the same halftone pattern. In daily printing, the absolute value we expect is% except for dot enlargement

now, it is not a problem to choose 280 or 305 lines/inch eyes made of 34 micron diameter wires. They have the same fiber height and the same diameter. We don't know the actual number of eyes after tightening, nor the percentage of blank parts after tightening. This is mainly because there are 15% fibers in each inch of the line in each direction, so the eye with 280 lines/inch will stretch longer than the eye with 305 lines/inch, and its blank part will be larger than the eye with 305 lines/inch when it is tightened

as the number of dots per square inch increases very fast, we also need to consider the number of lines we print. For example, the number of points corresponding to 50 lines/inch is 2400 points/square inch, 55 lines/inch is 3035 points/square inch, 60 lines/inch is 3600 points/square inch. When the number of printing lines increases to 65 lines/inch, the number of points per square inch surges to 4225. With the increase of dot density per square inch, we face more difficulties in the control of dot expansion. Besides mechanical dot expansion, we also need to solve more problems of optical dot expansion

lost point enlargement

there are at least three things we can do to reduce the mechanical and optical point enlargement of any number of lines. The first is to use wet white highlights or clear white templates at the end of printing. This transparent/translucent white can be mixed with wet colors to produce a color. This can effectively reduce or eliminate the optical and mechanical point expansion of the highlight part, and also make the transition of the tone more natural, reducing the point shape we see on the print. This is a great advantage for the printing of facial images and charts containing flesh tones

second, we can add some high-density substrates (higher than 3% by weight) to the ink. This will not make the ink look thick, but also can effectively reduce the dot expansion. When using lines with a diameter of 34 microns to make eyes with more 280 lines/inch of blank parts, we can see a better tone structure and a reduction in dot enlargement

third, we can mix the number of lines in the color separation graph. For example, if we have many problems in the control of black, we can only reduce the number of lines in the black version (from 65 lines/inch to 55 lines/inch), This also reduces the density of points (from 4225 points/square inch to testable performance indicators: upper yield strength, yield strength, maximum force, tensile strength, specified non proportional extension strength, modulus of elasticity, elongation after fracture 3025 points/square inch). At a lower number of lines, the points are more scattered, thus reducing the point expansion in the same area. This is a very attractive option. Because black ink is often designed in dark areas, the effect of bold dots is not as obvious as in bright areas, such as areas where flesh or light colors appear

many variable factors affect the degree of dot enlargement in the printing process. But if we are willing to spend time measuring and managing them, we will certainly get high-quality products

Author: simple

source of information: must win

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