Efforts should be made to reduce the amount of dusting used in printing.
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In printing, dusting is used to prevent smudging on the back of the product. Nowadays, many advanced printing equipments have eliminated the powder spraying device, and adopt three-group drying method, namely: two sets of infrared and one set of ultraviolet. At present, most of our domestic printing equipment is also infrared spray powder or only dust spray device.
Usually when the ink layer is thick and the dark area is large in the production, the printing operator always wants to put the amount of powder larger, so that the product will not be scrapped because the back is dirty, but often the powder is neglected. May be small this problem. In fact, too much powder will bring a lot of harm.
1. The amount of powder is too large. When the front and back are printed, the amount of powder on the front side will be directly affected. In severe cases, it is necessary to clean the blanket every few hundred sheets. The product will therefore be unstable in color, affecting both quality and yield.
2. The amount of powder is too large, affecting the gloss of the product. When printing some high-end products, the operator always wants the ink saturation to be higher. The printed products are both bright and bright, and at the same time increase the amount of powder in order to prevent smudging. The powder is absorbed by the ink on the ink layer which has not been dried, and a mist is formed on the color, and the gloss of the product is thus lowered.
3. The amount of powder is too large, and the wear on machinery and equipment is serious. In the production, while spraying powder to the product, a considerable amount of powder is flying to the machine's delivery chain, gripper and roller. Although there are maintenance times every week, it may not be able to clean up all the dust. Over time, it will inevitably increase the wear and tear on the machine.
4. The amount of powder is too large, which will have a certain impact on the health of the operator. Although the sellers say that the powder is harmless to the human body, the operator stays in the tiny dusty workshop every day, and the lungs do not know how much dust to inhale.
5. If the amount of powder is too large, it will also affect the processing of the post-process, such as light coating.
Therefore, in production, we should pay enough attention to the amount of powder used, and spray the nozzle as little as possible to achieve the purpose of controlling the back surface. There are many factors that cause back smudging in production, and the key is how to effectively control it.
1. Strictly control the density value. The value of each color density is obtained by proofing, and the K value, the dot gain value, and the saturation of the ink color are taken to obtain an optimum value. In the other sense, the optimum value (density) obtained by this method is also the optimum amount of paper to withstand the ink. For example, the best density values we obtained with 128 grams of Japanese coated paper are yellow 1.05, red 1.35, blue 1.45, black 1.70. We can keep this data for printing in production. Under normal circumstances, it is impossible to get dirty. Adding a small amount of dusting will be more insurance. However, the density is excessively high, and even if the ink layer is not thick, it will still be dirty. For example, compared with the 100% overprinting of yellow and magenta and the overprinting of four colors, it is obvious that the 100% ink layer of each of yellow and magenta is not thick. If the yellow density value is increased by 1.30 or more, the magenta density value is increased by 1.50 or more. Exceeding the critical value of the paper's ability to withstand ink, the product is very easy to smear on the back.
2. The reason why we use powder is because the dark area of the product is large and the ink layer is thick. In the case of such manuscripts, we should use the plate-making method to reduce the dark-adjusted ink layer by using the plate-making method as much as possible. The ink quantity is controlled between 235% and 270%, which is 125% to 90% less than the total ink volume of the conventional method, so that the density requirement of the dark adjustment can be ensured, and the intermediate darkness is not affected by the excessive amount of ink reduction. Adjust the level. According to relevant data, the total ink volume of 235% and the total ink volume of 360% reduced the ink volume by 125% and the density values shown were substantially similar. When the actual dark amount of total ink is 235%, the printing can control the back side dirty without spraying powder or a small amount of powder.
3. The proofs are the customer's credentials and the basis for printing. If the printed product and the sample are too large, the customer will refuse to accept it without any politeness. The question is whether the proof reflects the original. For example, the original ink layer is not so thick, and the amount of ink is desperately increased in order to achieve user satisfaction when proofing or signing. This will cause the outlet to expand severely. The expansion of the outlet will spread from the center to the surroundings. The ink in the center will definitely exceed the amount of paper, so it is difficult to avoid smudging without increasing the amount of powder.
4. Ink emulsification will seriously affect the drying time of the product. When the ink contains a certain amount of acidic aqueous solution, it will prolong the time of oxidizing and conjunctiva on the surface of the blot, resulting in slow drying and easy to cause backside smudging. There are many factors that cause severe emulsification of the ink, but the most important thing is water, and at the same time control the amount of ink. The minimum amount of ink and the minimum amount of water should be used when a certain density value is reached, which is the best way to control the severe emulsification of the ink.
5. The printing pressure is too light, so that the ink cannot be transferred normally. The ink transferred to the paper cannot be well bonded to the paper. The ink only floats on the surface of the paper, which is not strong and can cause the back to become dirty. Therefore, within the normal range of outlets, the printing pressure should be appropriately increased.
In summary, we need to use less dusting or no dusting to control the back smear. We must carry out serious process research from the original, formulate an effective process construction plan, and make the original plate suitable for printing through plate making. Standard proofs. In the printing, it is necessary to strictly follow the data processing operation, control the density value, pressure and ink balance of each color, maintain a certain printing speed, appropriately increase some dry oil, and reduce the height of semi-finished products.