Main measures to reduce the amount of dust used in the printing process

In order to prevent the back of the printed product from being dirty, we can't rely solely on the excessive amount of dusting to ensure that we should try our best to start with raw material procurement, production process control, etc., with little or no dusting. In my opinion, the main thing to note is the following.

(1) Before organizing production, it is necessary to select paper that is easy to dry according to the characteristics of the printed product. Acidic paper, a small amount of art paper will delay the drying time of the ink, and should be carefully selected.

(2) Strictly control the printing density value of the ink. According to the People's Republic of China press and publication industry standard "Quality requirements and test methods for lithographic prints", for the solid density of fine prints, yellow is required to be 0.85 to 1.10, magenta is 1.25 to 1.50, cyan is 1.30 to 1.55, black is 1.40. ~ 1.70; For the solid density of general prints, yellow is required to be 0.80 to 1.05, magenta is 1.15 to 1.40, cyan is 1.25 to 1.50, and black is 1.20 to 1.50. For book-based printing companies, it is recommended to use this data for printing, rather than artificially increasing the ink density or increasing the thickness of the ink layer. Thus, according to the author's experience, there are many papers with better drying performance that can be used without or with less powder. For printing companies mainly based on albums or packaging, it is recommended to establish their own printing characteristic curves according to different types of printed products and raw and auxiliary materials to determine the appropriate printing density value.

(3) Adopt a ground color removal process to reduce the amount of ink in the dark spot. Why so far, Even offset printing machine equipped with an infrared drying system, also need to use dusting it? The reason is that there are a lot of large darkened area of printed materials, ink thickness, it is difficult instant dry. When encountering such manuscripts, under the premise of not losing the importance of the darkness of the original, the plate-making method should be used to reduce the dark-adjusted ink layer by using the background color removal process, which can save the high-priced color ink and reduce the darkness. Adjusting the total thickness of the ink layer in the region can improve the ink printing suitability, improve the quality of the printed product, reduce the production cost, and use no or less powder to control the back of the printed product.

(4) Do not increase the amount of ink and the amount of powder sprayed by one-sided pursuit of the fullness and vividness of the printed color. For example, there is not such a thick ink layer on the original, and we often desperately increase the amount of ink in order to satisfy the customer when proofing or signing. This will result in a serious dot gain or dark adjustment of the thickness of the ink layer, which is beyond the range that the paper can withstand, forcing the operator to increase the amount of dust sprayed. This is a practice that ignores the actual situation and asks for it. It should be avoided.

(5) Correctly grasp the balance of ink and ink to prevent ink emulsification, otherwise it will seriously affect the drying of printed products and be forced to increase the amount of powder sprayed. When the ink contains a certain amount of acidic aqueous solution, the time for oxidizing the film on the surface of the blot is prolonged, which causes the printed product to dry slowly and easily cause backside smudging. Therefore, ink emulsification should be strictly controlled, and when a certain density value is reached, the minimum amount of ink and the minimum amount of water should be used.

(6) Master the correct printing pressure. If the printing pressure is too small, the ink will not be transferred normally. Even if it is barely transferred to the paper, the ink will not bond well with the paper. The ink will only float on the surface of the paper, and it will not penetrate and dry, which may cause the back of the printed product to be dirty. Therefore, the printing pressure should be appropriately increased under the premise that the outlets are increased in the normal range.

(7) Do not add too much varnish or degreaser to the ink. Because such additives can improve the ink printing suitability, it will also hinder the oxidation and film formation process of the ink, delay the drying time, and force the operator to increase the amount of powder spray.

The above content is selected from the 10th issue of 2015, Digital Printing Art of Keyin Media. For more journal content, please pay attention to the journal channel.