In today's gravure printing industry, 95% of manufacturers use conventional mechanically engraved ink rollers to print high quality image products (Braswell, 2000). Can this situation improve? Of course, there is a way to improve the printing quality by improving the ink roller. In this paper, five different sculpting ink rollers were experimentally studied. Conventional Diamond needles and Honeycomb Diamonds were used to engrave six different ink rollers, and the ink rollers were different. Ink, different substrates, and printing effects under different engraving conditions were tested. The results show that "cellular technology" helps to improve the quality of printed products.
The basic theory of the HC (hexagonal diamond) needle has been around for 7 years. In the United States, the intaglio printing industry consumes 8 to 10% of the total diamonds on average. The HC sculpting needle is actually not mysterious. It differs from the CD (normal diamond) sculpting pin in that its needle tip is flat and forms a flat tip. It can be carved in the hexagonal honeycomb flat bottomed ink hole. Figure 1 is a schematic diagram of a HC ink hole with a 120 degree engraved needle.
As shown in the figure, the volume of the ink holes carved with HC diamond is reduced by about one-third. However, in theory, HC ink holes release more ink than conventional diamond ink holes. Existing research results show that increasing the ink transfer speed of the ink roller helps to improve the printing quality and reduce the ink consumption. If this is combined with the flat bottom of the HC ink hole, we have reason to believe that the HC engraving ink hole is a better method between laser engraving and electromechanical engraving. Straight HC stylus needles of any size or angle are now available on the market, and most deliveries guarantee that their product tolerances are limited to ±5 μm.
Experimental purpose The research data provided in this paper aims to evaluate the effect of HC ink roller on the color density, dot reproduction, tone reproduction, ink weight, and printing brilliance of printed materials on different substrates.
Experimental Scenarios This experiment used six different ink rollers carved by RJR Packaging of Winton-Salem, North Carolina to evaluate the impact of HC Diamond engraving ink holes (flat edges) on printing under different conditions:
Engraving method I
Using an ink roller, the engraving conditions are shown in Table 1. The ink roller test was RJRP's GMS printer. The substrates were Mylar (5mill) and 54 pound CIS paper. A standard nitrocellulose ink with an ink viscosity of 23.
Table 1 Engraving conditions (I) Ink roller diameter Mesh line compression amount Diamond angle Flatness ink channel Hole width 1 8.675†188 39 110 25 μm 0 10 153 1 8.675†188 39 110 0 μm 0 10 153 Engraving method II
Using an ink roller, the engraving conditions are shown in Table 2. The ink roller test was an RJRP GMS printer using a 54-pound CIS paper and a standard nitrocellulose ink with a viscosity of 23.
Table 2 Engraving Conditions (II) Inker Roll Diameter Mesh Compression Amount Diamond Diameter Tip Taper Hole Wall Hole Wall 2 8.675" 188 39 110 5 μm 0 10 153 2 8.675" 188 39 110 15 μm 0 10 153 2 8.675" 188 39 110 25 μm 0 10 153 Engraving Method III Using two ink rollers, the engraving conditions are shown in Table 3. The test was performed on RJRP's 10-color Rotomec printer using 48 GA PET material and a standard polystyrene ink with a viscosity of 17.
Table 3 Engraving conditions (III) Inker diameter Diameter of wire roller Compression amount of diamond Angle of flatness Dimension of ink channel Hole width 3 10.505†188 40 115 0μm 0 9 155 4 10.505†188 40 115 25μm 0 9 155 Engraving Method IV
Using an ink roller, the engraving conditions are shown in Table 4. On RJRP's 10-color Rotomec press, 26 pounds of clay-coated, standard nitrocellulose ink with a viscosity of 17 was used.
Table 4 Engraving conditions (IV) Ink roller diameter Mesh line compression amount Diamond angle Flatness ink channel Hole width 5 9.9475" 188 40 110 5 μm 0 10 155 5 9.9475" 188 40 110 15 μm 0 10 155 6 9.9475" 188 40 110 25μm 0 10 155 Engraving Method V An ink roller is used and the engraving conditions are shown in Table 4. This was done on a four-color Cerutti press from RJRP, Tipping Paper and standard ink.
Table 5 Engraving conditions (V) Ink roller diameter Mesh wire compression amount Diamond angle Flatness ink channel Hole width 5 11.615†14 40 110 25 μm 32 14 21 Results and discussion Experiments using X-rite densitometer (528 type) The color density, mottle, and color shift of the prints were measured.Figure 1 is a plot based on the data from the GMS press and Mylar material printed in engraving I.
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 The 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 Sculpting Mode III Test Results 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 the standard deviation from the L, C and H color values To investigate, ordinary CD cutting needles are higher than HC diamond cutting needles. 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 the engraving method V on the sticky paper Roll number and total value Operator[gr] Center[gr] Drive[gr] Volume 1# 1455.47 146.50 145.32 Volume 13# 147.32 148.36 148.79 Total 15 samples (volume 1#) ) 437.29 Sum of 15 samples (Volume 13#) 444.47 Difference 7.18 Conclusions and Recommendations Based on this study, 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 selection 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. (Source: Besson)