The most popular use of control strip densitometer

2022-08-02
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Control strip and densitometer are used for printing quality management (III)

two laws can be learned from the point increase theory on one side:

first, 5% ~ 95% of the points are different in size and edge length, so the point increase is different. Using Murray Davies formula to calculate the point increase, it can be seen that the edge of 50% point is the longest, so the increase is the most

second, the outer length of the thin line point is greater than the outer length of the thick line point, so the thin line point is larger than the thick line point. For example, 175 lines/inch is larger than 150 lines/inch, and 200 lines/inch is larger than 175 lines/inch

b. The optical point increase is completely caused by the light reflection. The point increase in the range of 75% ~ 80% hue value is quite large according to the density seen by people and displayed by the reflection densitometer during proofing and printing. The increase of optical point is caused by the scattering of incident light at the edge of the dot ink film, the internal reflection of the paper, and the reflection of light with ink from the outside of the point. The increase of optical point depends on the transparency of the ink and the smoothness, absorption and other surface states of the paper

because people can only see the point increase on the surface visually, but the maray Davies formula takes into account the mechanical and optical point increase at the same time. Ashley densitometer automatically calculates the point area and point increase by using Marley Davis formula. Marley Davis formula: Point area = [(-dt)/(-ds)] × 100%, where DT is the point density minus the paper density, and DS is the field density minus the paper density

(4) fine point micro measurement section, as shown in the figure

fine point micro measurement section is also called ultra micro measurement element, which is the core part of Bruner system. The thin segment is composed of 60 lines/cm of equal width broken lines, with a total point area of 50%. The thin segment uses equal width cross lines to divide the thin area into four. Each 1/4 area point is formed exactly the same, but in different directions. Its main functions are as follows:

① the outer corner of each 1/4 grid is composed of 6 lines/mm of equal width broken lines, which is used to check whether there is sliding deformation and ghosting at the printing time point. If the lines at the four corners of the sample sheet are deformed, it indicates that the printing points have slipped. Horizontal sliding, the vertical line becomes thicker; It slides vertically and thickens horizontally, which is very intuitive

② there are 13 points in the first row near the crosshair. The points in the inner row are small black points from large to small, and the corresponding 12 hollow white points from large to small, which are 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 8%, 10%, 12% and 20% respectively. The positive points and negative points are arranged correspondingly, as shown in Figure 3

judge the point change of printing, proofing and printing. It describes the critical pressure of chemical resistance (OC) in megapascals (MPA), that is, the critical pressure of cracks after 15 minutes of contact with some chemical reagent. You can observe it with a 25 times magnifying glass. If you can sun 10 small black spots with PS plate, 2% of the small spots are complete. The exposure and development of standard plate printing should reach the corresponding alignment of yin and Yang points. During proofing and printing, if there is no densitometer, the data can be increased by visual inspection points. Observe how many translucent small white holes are left, indicating how much the points are increased. If all 12 small white holes are dead, it means that the point increases by 20%. If 10 small white holes are stuck and 2 small white holes are left, the point increases by 15%; Four small white holes are left, indicating that the point is increased by 10%. 4 small white holes shall be reserved in general proofing specification

③ there are four 50% standard square points in each 1/4 block, which are used to control the depth change of the layout during printing, proofing and printing. If 50% of the standard square points have a large overlap angle, the points will increase; On the contrary, if the four corners are disengaged, the point will be reduced. Belt pulley is connected with electromechanical drive

(5) thin wire and small dot control section, as shown in Figure 4

thin line and small dot control sections have two aspects: one is at 6mm × The 7mm area is divided into 6 grids, and the grids are arranged in sequence with 0.5%, 1%, 2%, 3%, 4% and 5% of 15 lines/inch points. When printing, proofing and printing, the reproduction data of dots can be standardized according to the printability of the company. Generally, the specifications for the sun proofing version of the product are 2% dot out, and the sun proofing version is 3% dot out. The second is the resolution line detection mark composed of fine horizontal lines and vertical lines, which are 6 μ m、8 μ m、11 μ m、13 μ m、16 μ M 5 sections, used to test the exposure, development standard and PS plate resolution of the printing plate. The standard for general sun proofing is 6 μ M not out, 8 μ M is aligned, and the corresponding 2% dot is aligned. The standard for general sun printing plate is 8 μ M not out, 11 μ M is aligned, and the corresponding 3% dot is aligned

(6) ash balance observation section, as shown in the figure

at 6mm × Within 7mm area, the gray balance section composed of 50%c, 41%m and 41%y is arranged next to 50% of the black dot blocks. It is possible to visually observe whether the gray tone of the three color overprint is consistent or close to the gray tone of the nearby black dot

(7) 25% point segment, as shown in the figure

is used to detect the change of dot tone in 1/4 bright tone area, and can draw the dot increase curve of this area together with 50% and 75% dot blocks

to sum up, Bruner control strip has fine design and sensitive response. It can not only measure and calculate various parameters with densimeter, but also determine various data with visual inspection. As long as we make full use of the testing tools that laboratory machine manufacturers want to occupy a stable market position, standardize process parameters, and carry out data management, the quality can be stabilized and improved, which is different from that of steel wire

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