How much do you know about package offset printing (153-162)

153 how to calculate the amount of ink preparation?

The amount of ink to be formulated is slightly more than the actual amount, but it should be controlled within the lowest range to avoid wastage. The amount of ink transferred can be calculated according to the following formula:
Ink transfer quantity = print volume × print area × unit area ink consumption + remaining ink volume The printing area refers to the spread area of ​​the ink on a single print. If it is a halftone image, the image area should be multiplied by the dot percentage. The amount of ink consumed per unit area depends on the thickness of the printed ink layer and the absorbency of the paper. The adjuster should have an approximate estimate of the amount of ink required for a particular paper and image. In my personal experience, a large area of ​​about 5 million cm2 of ink was used to print 1 kg of ink on coated paper. Printing screen images are thinner in the ink layer and less ink consumption; the unit area of ​​printing non-coated paper consumes more ink. There should be some remaining ink after the printing is completed, otherwise the last part of the printed sheets cannot get normal and uniform ink supply. If printing a large area on the ground, the remaining ink should be more corresponding; printing a small area of ​​the image, the remaining ink can be less. The amount of ink transferred is also related to the density of the ink. The ink consumed for printing is related to the volume. If the ink has a large density, the amount of ink used is larger.

154. What should we pay attention to when deploying ink?

The order of adding inks should be from large to small, that is, a large proportion of main ink should be added. The deployment of pale ink should be preceded by a diluting agent, and then dark ink should be gradually added to the diluting agent. There are two methods for blending inks: blending a small amount of ink can be done with manual mixing; blending a large amount of ink should use mechanical mixing.

155. What should I pay attention to when applying ink?

1 Since there is a big difference in the color rendering effect of the same ink on different papers, the ink sample should be coated with the paper that is to be used in the same batch of jobs.
2 The thickness of the ink layer has a great influence on the color appearing. It is necessary to strictly control the thickness of the ink layer coated with the ink to match the thickness of the ink layer to be printed. This requires a lot of experience.

156. Contrast to evaluate the color of the ink should pay attention to what?

1 light source. To evaluate the ink color under the light source with excellent color rendering, the conditional factory should be equipped with a D65 standard light source.
2 look like method. To fold or tear the coated ink sample off the blank edge of the ink sample, place the color and color sample to be evaluated on the ink sample (color on the chromatogram or the color of the original) close together in the same field of view , carefully assess under a magnifying glass.
3 Original color sample If it is coated, calendered, etc., it should be coated with a transparent adhesive film and then compared with the color sample.

157. What is the hiding power of ink?

The hiding power of ink refers to the ability of the ink to cover the background. The stronger the hiding power, the lower the transparency of the ink. Four-color printing requires high transparency of the ink, otherwise it will affect the color reproduction of the print.

158. The hiding power of ink and what factors?

1 ink's own performance. Mainly depends on the ratio of the refractive index of the pigment and the binder in the ink. The closer the ratio is to 1, the higher the transparency.
2 Ink emulsification during printing. The more serious the emulsification, the worse the transparency and the more turbid the color.

159. Adjustment of printing ink suitability includes what content?

What is often needed in production is the adjustment of the ink drying speed and the adjustment of the ink flowability. The adjustment of fluidity is mainly based on the adjustment of ink adhesion and viscosity.

160. What is the adhesiveness of ink?

The adhesive property of ink refers to the ability of the ink film to prevent itself from being broken and broken during the transfer process. The essence of the ink is a performance of the cohesion of the ink under the action of adhesion.

161. What is the effect of ink stickiness on offset printing?

1 Adverse effects caused by excessive ink stickiness: When the surface strength of the paper is not high enough, the phenomenon of “pulling” and “peeling” of the paper easily occurs; the ink is transferred and transferred badly; the ink layer is unevenly distributed; Uneven phenomenon.
2Inadequate ink adhesion may cause ill effects: the cohesion of the ink is not large enough, and the broken silk will not rebound, resulting in a poorly-printed and increased dot of the printed product. The level of the copied image will be lost and the resolution will be poor. Easy to emulsify.
3 When the multi-color machine wets wet and overprints, the adhesiveness of the previous color ink must be larger than the latter color, otherwise the ink to be printed first will be “stripped off” by the ink after printing, resulting in the phenomenon of “reverse overprinting”.

162. According to what factors in the printing ink adhesion?

1 The surface strength of the paper. The surface strength of the paper is large, and the ink adhesion can be adjusted to be larger. On the contrary, the adhesiveness should be adjusted smaller. Otherwise, the paper “drops powder” or “lint down” is very severe, which seriously affects the product quality and production efficiency. This is often regulated. The main motivation for ink adhesion.
2 printing speed. When the speed is high, the adhesive deployment requirements are smaller, and vice versa. The faster the speed is, the more likely it is to “pick up” the phenomenon and spread the ink unevenly, and it is necessary to reduce the adhesiveness to suit it.
3 layout text structure. When printing halftone images, the most important thing is that the shape and area of ​​the dot should be correctly reproduced, and the adhesiveness should be adjusted to be larger. When printing real-time images, we hope to get a uniform and solid field, and because there are no dot gain problems, the adhesion must be smaller.
4 workshop temperature. When the temperature rises, the cohesive force of the ink will decrease, and problems such as increased emulsification and increased dot gain rate are more likely to occur. When the ink is adjusted, the adhesiveness of the ink should be adjusted in advance. Conversely, adjust the ink adhesion.

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