Control of the most popular types of network expan

2022-08-01
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Control of type of point expansion

signal bar: it is mainly used for human visual evaluation of printed matter. Its function is relatively single and directly expresses the appearance quality information of printed matter. Such as GATF star, GATF digital signal strip, color signal strip, etc. invented by the American Printing foundation

test strip: a multi-functional marking element based on densitometer detection and evaluation, which usually combines visual identification with densitometer test, and with the help of charts, can carry out numerical calculation according to "experimental information", "experimental time", "experimenter" single or combined query curve. Such as Bruner test strip

control strip: it is a multi-functional control tool that combines visual evaluation and test evaluation of signal strip and test strip. For example, Bruner's third generation test strip

1. Formation of dot enlargement

classified according to the state of dot enlargement

1. Linear enlargement: refers to the enlargement of the edge of the printing point in one direction. Originally, the printing point is square, prismatic, circular and chain. Linear enlargement refers to the linear enlargement of the point in a certain direction

2. Expansion of area:

the printing point expands to the surrounding area, and the expansion of the point area is generally proportional to the length of the point edge. In other words, when the area of the point is large, the length of the edge of the point also increases

3. Density increase:

the density increase is proportional to the area of the printing point. The density increases and the ink color is large; If the ink color is large, the dot area will be large

classified according to the point change of printing

1, normal expansion. This kind of dot enlargement is allowed, that is to say, dot normal enlargement, high density of center position and low density of edge position

2. Ghost point. This expansion of printing points is not allowed. Point ghosting occurs during printing, which seriously affects the color rendering effect of points

3. Irregular dot enlargement. When irregular dot enlargement occurs, the printed dot does not have a rule, and the dot expands around. At this time, it is easy to have pasted and dirty plates, which will affect the quality of printed products. Such irregular dot enlargement is not allowed. The point expansion range shall not exceed 15%, 12% and 10%

II. The relationship between the number of lines in a point and the length of the edge

since the point change occurs in the surrounding part of the printing point, the more points per unit area, the more surrounding parts of the point, and the greater the change of the point. It can be seen that the point expansion of the thin line is larger, while the point expansion of the corresponding thick line is smaller

printing points can be classified into coarse points or fine points according to the purpose of the wind. Fine points should be used for fine printing products viewed from a close distance, such as periodicals, pictorials, trademarks, etc. Coarse dots are used for fine printing products viewed from a distance, such as large advertising stickers, posters, etc. Points are in inches. That is to say, within an inch area, common lines include 60 lines/inch, 90 lines/inch, 133 lines/inch, 150 lines/inch, and 175 lines/inch

for example, the dot area is also 60%, the blank area is 40%, one is 60 lines/inch, and the other is 175 lines/inch. The dot expansion of 175 lines/inch will be much larger than that of 60 lines/inch. This means that the edge length of the 175 line/inch thin line is long, so the point enlargement is larger. 60 lines/inch thick lines have shorter edge length, so the point enlargement is smaller

III. signal bar control point expansion

gatf digital signal bar

gatf digital information bar is made up of 27 lines/cm thick dots as the substrate, and 80 lines/cm tiled numbers from 0 to 9 are embedded in the middle. On the original version, the density of digital 2 in the signal bar is the same as that of the background color

the specific use is as follows:

1. GATF digital signal strip assumes that the thickness is unchanged and the point is not enlarged. Observe the density difference between the number and the background color with the naked eye

2. In the original version, the area of digital points is supplemented and decreased by 3%-5% and more than 5%. The area of point 0 is the largest and that of point 9 is the smallest

3. Since it is assumed that the thick line is not enlarged at all, the dot enlargement amount is determined according to which number has the same density as the background color

example 1: Digital 5 has the same density as the background color. At this time, starting from data 2, the digital has transferred the three-level printing point (taking 2 as a reference without expanding the fixed point, the transfer three-level decreases by 3%-5%), indicating that digital 5 has expanded the point by 9%-15%

example 2: the number of GATF signal bar is 1, which is the same as the background color density. Taking the number 2 as the reference, the first level is transferred, and the point is reduced by 3%-5%

calculated with reference to data 2. Before 2, the point was reduced, and after 2, the point was expanded

point control of measuring scale

36 wedge-shaped lines with equal black and white width are radiated outward from the center of the circle, and there is a small whiteness in the center of the circle

The

star Mark determines the size of the expansion of the fixed point according to the size of the central white point

large white dot in the center indicates the size of dot expansion

a small white dot in the center indicates a large dot expansion

The

star mark is suitable as a test tool for test point expansion. Its function is to identify the type of point expansion

1. The small white dot in the center of the star sign is oval, indicating that the dot is directionally enlarged. When the small white dot in the center of the star shows "→ 0 ←", this kind of ellipse indicates that the dot expands left and right, which is called horizontal expansion; The point presents an "O" that is called an up and down enlarged point. Or vertical expansion

2. If there is ghosting in the center of the star Mark, the small white dot in the middle will not only become smaller, but also appear "8" or "∞" shape, indicating point ghosting and paste

to sum up, GATF data signal bar is characterized by providing a data. Point enlargement gives a quantitative value, while the star marker can identify the type of point enlargement. Both have their own uses and benefits. They can be used both ways to learn from each other

the description of fixture in gb13022 ⑼ 1 test method for tensile properties of plastic film is as follows: "The experimental machine should be equipped with appropriate fixtures and test strip control point expansion

in the process of printing and plate printing, when the test strip controls the expansion of the printing point, the Bruner test strip is the most widely used.

composition of Bruner test strip:

50% 50% 75% 75% on-site fine thickness: indicates the fine point thick: indicates the coarse point

Bruner test strip takes the thick line point as the same and does not expand as the reference.

Calculation basis for point enlargement

1. Taking the thick line as the reference comparison section, Bruner tests and destroys the fixture: generally, the electro-hydraulic servo universal experimental machine is only equipped with 30 lines/inch thick and 150 lines/inch thin of the fixture strip for standard samples. Therefore, the point enlargement of the 30 line/inch thick segment is ignored, and the 30 line/inch thick segment is set to have no point enlargement

2. The characteristic curve of density and point area is used.

according to dr=tg1/1-a

a=-dr

it shows that the density value is equal to the area difference

when testing with Bruner test strip, use a densitometer to measure the coarseness first, then the fineness, and then the fineness - coarseness = point enlarged value

calculation method of Bruner point enlargement

1. Select 50% of the test points

point enlargement = (fine density - coarse density) × 100% = D fine and coarse

(where: D means density)

2. Select 75% of the test strip

point enlargement = (fine density - coarse density)/2 × 1. Low or even less than 10000 times 00%

advantages of the calculation point expansion of Bruner method

1. Bruner test strip is easy to calculate

2. It can eliminate the test error. If there is absolute density error during the test. There are absolute errors in both fine and coarse points

point enlargement = (d fine coarse) × 100%

3. As the coarse and fine are measured at the same place at the same time, the drying conditions of the ink are the same, which is less affected by the printing ink, so it has nothing to do with the wet drying of the ink

the disadvantage of using Bruner test strip method to calculate point enlargement

1, there is absolute error. It uses a = 1-10-dr

this formula assumes that the ink is completely absorbed on the paper and the paper is completely reflected. However, in the actual printing process, it is absolutely impossible to absorb 100% of the ink, and the whiteness of the paper is different, so it is impossible to achieve 100% total reflection

when the point is enlarged (50%) = (fine coarse)/dr × 100%, at this time, the Bruner test strip cannot be tested

2. There are certain limitations

50%, (0.3-0.5) if it exceeds this range, it will not work

75%, if the (0.6-0.8) point expansion exceeds 15%, it cannot be calculated

selection of test points

1. The test points shall be arranged at the place with the largest point expansion (50% of the points)

2. Try not to select the test point at the angle between points. Because the corner is unstable. Jump occurs when the point at the corner is enlarged

principles for selection of test points

1. For intermediate tones: for originals with rich subtle levels and high quality requirements, 40% and 50% of test points can be selected

2. For ordinary products, 75% of test points can be selected

error of test points

1. Currently, the Brunner test strips are generally copied, and there is copy error

2. The test strip is generally used in monochrome, so there is overlapping error

in addition, the first, second and third generation Bruner test strips have been widely used by various printing manufacturers so far. The third generation Bruner printing test control strip, developed in 1984, is divided into 7 sections and can be extended according to the required size. The content of control strip test includes: Color Code: 25% - 75% section; Bruna section III field, 50%, special micrometer section; Neutral ash reduction section; Printing degree reduction section; Plate resolution section; Four color three section test section

has the following test functions: measuring the density of the ink layer; Expansion of monitoring points; Check the deformation and ghosting at the printing time point; Determine whether the resolution and exposure of the printing plate are accurate; Control the specific changes of the layout depth during printing, proofing or printing; The distance between the parallel range of inspection points and the area of different points; Control of printing fine spots; Ash balance detection; Detection of overprint percentage; Detect the density and hue of black restored by three colors y, m and C; Test the printing density of monochrome ink

in actual production, the test strip is widely used in plate making, such as plate printing, proofing, printing and mechanical debugging

v. items detected by Bruner test control strip

1. Image definition; 2. Whether the printing overprint is accurate; 3. Control of contrast of printed matter; 4. Reproduction of printing tone; 5. Color reproduction of printing ink; 6. Detect mechanical equipment failure; 7. Detection and evaluation of ghosting; 8. Expanded range and types of points. (WangXinCheng) (China packaging daily)

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