"Cellular" Technology to Improve Gravure Printing Effect (II)

Results and Discussion <br> In the experiment, the X-rite densitometer (Model 528) was used to measure the color density, mottle, and color shift of the prints. FIG. 1 is a graph drawn according to the data of the printed product of the GMS printing machine and the Mylar material in the engraving I. FIG.

From the graph, we can find that the color density value of the HC curve (blue) is 0.098% higher than that of the conventional diamond (red curve). This means that the printing density of the "honeycomb" ink roller is 0.1% higher than the original when the ink volume is reduced by 33%!

Graph 2 is the performance of the above example on paper printing materials. The graph also shows that the HC ink hole color density increased by 0.095%.
The results of the engraving II show that the color density of the printed material increases as the engraving needle increases at 5, 15 to 25 μm. This shows that the larger the HC needle is, the better the ink transfer effect is.

In the figure, we also find that the 15 μm color density curve (red) is on average 0.157% higher than the 5 μm curve (blue), and the 25 μm curve (green) is again 0.087% higher than the 15 μm curve. This shows that the flatter the tip, the smoother the bottom of the ink hole created by the engraving, the more ink is released.

In order to determine the effect of the flat tip on the mottle, we used a 2 x 2 inch large solid block for analysis. However, in the analysis, it was found that when the engraving process was performed, the diamond cutting pin was broken, so the data of the 25 μm needle was inaccurate. However, the 5 μm and 15 μm needles are exactly as shown. Table 6 shows the measured (mottling) density and standard deviation of the densities of the 5, 15 and 25 μm needles in the engraving method II.

Table 6 Data measured on engraving method II on CIS paper (54 lb) HC (5 μm) HC (15 μm) HC (25 μm)
1 1.344 1.613 1.580
2 1.339 1.609 1.552
3 1.287 1.620 1.555
4 1.371 1.627 1.570
5 1.366 1.631 1.579
6 1.346 1.631 1.581
7 1.371 1.600 1.633
8 1.344 1.651 1.625
9 1.414 1.661 1.575
10 1.372 1.598 1.621
Average density 1.36 1.62 1.59
Ink blot 0.033 0.021 0.029

In Table 6, from 5 μm to 15 μm, the color density increased by an average of 0.3%, while the 25 μm value was lower due to the diamond burst color density. The measurement of mottled spots is similar. As the tip becomes larger, the spot decreases accordingly. Because the larger the tip, the more the ink is transmitted through the ink hole, the screen effect will be reduced, and the printing and lustre will be correspondingly improved.

Listed in Table 7 are the results of measurement of engraving method III using a spectrophotometer. For each ink roller, 20 times were measured under the same printing conditions.

Table 7 Test results of engraving method III
HC Diamond LCH CD Diamond LCH
Average color value 16.17 15.27 41.57 Average color value 16.09 15.30 41.65
Standard deviation 0.26 0.37 0.47 Standard deviation 0.31 0.39 0.58

Table 7 shows that from the standard deviations of the L, C, and H color values, the average CD kerf is higher than the HC diamond kerf. It can be inferred that HC diamond can produce a thicker ink film, so the printing color is more concentrated, the printing product is smoother, and the overprinting color is also better. Through the naked eye, we can see the same result, and HC is better than CD.

The results obtained from the engraving method IV of 26-pound clay-coated paper show that it has less effect on gravure printing and tone reproduction. All needle-stamped ink roller prints had almost the same density of color and dark spots, and the difference could not be detected by the instrument (< 0.02%). As shown in the graph of Figure 4, their halftone dot area is increased by 9%, while highlights are increased by 25%. The 25μm needle has a slightly improved reproduction performance due to the large amount of ink transferred.

Table 8 lists the differences between the total printed coating weights for fifteen CD and HC engraved inker roller print samples. As seen in Table 8, 1# is printed on CD, and 13# is in HC. For 15 samples of each 3 x 3 inch, the coating is an average of 7 grams. This again shows that the flat head of the HC sculpt needle can produce a thicker ink layer, thus increasing the print slickness and smoothness and reducing the mottle.

Table 8 Measurement results of engraving method V on sticky paper

Volume and Total Operator[gr] Center[gr] Drive[gr]
Volume 1# 1455.47 146.50 145.32
Volume 13# 147.32 148.36 148.79
The sum of 15 samples (volume 1#) 437.29
The sum of 15 samples (volume 13#) 444.47
Difference 7.18

Conclusions and recommendations Based on the research in this article, the following conclusions can be drawn:
1. Although the HC diamond produced a 33% reduction in ink hole capacity, its ink transfer speed was improved. The flat headed ink holes allow the release of the ink to be faster, resulting in a thicker ink film, reducing blotchy and increasing color density.

2. As the flat head increases (5 to 15 to 25 μm), the color density, dot area, and tone reproduction also increase. This has been confirmed in the film printing. For coated and uncoated papers, the situation needs further study. The fluid properties of the ink are the same as the shape of the indented ink roller, all of which play an important role in ink transfer.

3. We have noticed that the 25μm diamond cutting needles produce too much stress during processing and it is difficult to form true honeycomb holes (no ink channel). For this reason, we recommend using different sizes of flat tips for different situations. Solid ink roller use 15-20um needle, small ink roller can use 20--25μm needle.

4. The color density of web printed samples is higher than standard. This means that more additives are needed to copy the colors onto the printed material. Addition of more additives also contributes to the release of ink in the ink holes and saves expensive pigments.

As the study of this paper confirms, the well-known "cellular technology" is also very helpful in improving the quality of printed products. The benefits of HC Diamond for specific jobs under certain conditions have been demonstrated. Other degrees of diamond engraving needles, printing materials, flat type and ink on the printing effect need further experimental research. However, it must be borne in mind that the HC diamond carving needle is 60 to 80% more expensive than the ordinary CD carving needle.