Control the amount of dusting to ensure the quality of the print
We are a big printing company in Shenzhen China . We offer all book publications, hardcover book printing, papercover book printing, hardcover notebook, sprial book printing, saddle stiching book printing, booklet printing,packaging box, calendars, all kinds of PVC, product brochures, notes, Children's book, stickers, all kinds of special paper color printing products, game cardand so on.
For more information please visit
http://www.joyful-printing.com. ENG only
http://www.joyful-printing.net
http://www.joyful-printing.org
email: info@joyful-printing.net
In the printing process, especially when printing coated paper and fine prints of large ink screens, in order to prevent the back side of the printed matter from being dirty, the stacked upper and lower prints are separated, usually in the case of printing the last color. Powder device, or a combination of infrared drying and dusting device for dusting. The control of the amount of dusting is critical to the quality of the final print.
The hazard of excessive dusting
In daily production, in order to prevent the printed products from being scrapped due to dirty back, the operator habitually increases the amount of powder sprayed, resulting in more dusting on the surface of the printed product. As everyone knows that the amount of powder used is too large, it will bring a variety of hazards, mainly in the following aspects.
(1) If the amount of powder sprayed is too large, it will cause trouble for double-sided printed products. When the printing needs to print on the front and back, because the amount of powder on the front side is too large, the printing quality will be affected when the reverse side is printed. In the case of serious printing, it is necessary to clean the blanket once every few hundred sheets, which is not only time-consuming but also time-consuming. The printed matter has unstable ink color and powder spots.
(2) When the amount of powder is too large, it will affect the gloss of the printed product. When printing some high-end prints, we always hope that the ink color saturation is high, the color is bright and bright, and often the powder amount is increased in order to prevent smudging. However, if the powder is sprayed on the ink layer which has not yet dried, the ink layer will absorb a part of the powder, so that a layer of powder mist is formed on the surface of the ink layer, and the gloss of the printed product is rather lowered.
(3) If the amount of powder sprayed is too large, the wear of the printing equipment will be aggravated. During the printing process, as we continue to apply dust to the prints, a considerable portion of the dust will fly to the delivery chain, the gripper and the rollers of the printing equipment. Even if we carefully maintain the printing equipment 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 printing equipment.
(4) If the amount of powder sprayed is too large, it will have an impact on the health of the operator. Although in the requirements of green printing, most of the printing companies currently use dusting for plant dusting, the instructions indicate that the powder is not harmful to human health, but the operator stays in the fine dusty workshop all day long. It will inevitably cause certain damage to the human lungs. When the amount of powder is too large, the fine particles floating in the air will increase, and the damage will increase.
(5) If the amount of powder sprayed is too large, it will have a considerable impact on the subsequent process. For example, because the particles are coarse, if the amount of powder sprayed during the printing process is too large, the particles will float on the surface of the printed product. When the film is coated, the adhesive does not adhere to the ink layer at every place, but adheres to the layer. This causes a false sticking phenomenon that seriously affects the quality of the film. In addition, if the amount of powder is too large, it may cause problems such as hot stamping and smearing in the hot stamping process.
Main measures to reduce the amount of dust spray
In fact, in order to prevent the back of the printed matter from smudging, we can not only rely on the excessive amount of dusting powder to ensure, but also try 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 to 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 is the offset printing machine still required to use dusting even if it is equipped with an infrared drying system? The reason is that there are many printed products with large dark adjustment area and thick ink layer, which is difficult to dry instantly. 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.
In summary, we must carefully study the printing process from the receipt of the original, formulate an effective process implementation plan, and make a printing plate suitable for printing through the background color removal process at the time of plate making, and at the same time standardize, digitize and standardize. jobs. In the printing process, strictly follow the standard operation, control the density value of each color, printing pressure and ink balance, and maintain a certain printing speed, flexibly adjust the infrared drying system and the delivery drying system to reduce the height of semi-finished products, so that you can pass Use less dusting or no dusting to control the dirty back of the printed product. Do not rely solely on increasing the amount of dusting to solve the problem of dirty on the back of the printed product.