Discussion on the Prepress Production Experience of Waterless Offset Printing Process

As far as the entire printing industry is concerned, digital printing and waterless offset printing technology have developed rapidly in the printing field. Major printing press manufacturers have also introduced various digital printing presses on the market. Among them, the QM 46-4 DI introduced by Heidelberg combines the typical features of these two technologies and has a remarkable representation. In the long-term operation and use, we have summed up a few points of operation experience and experience, and discussed with the majority of printing colleagues.

The advantage of the DI technology is that, first of all, there is no need for film, and there is no need to print, shortening the printing period and reducing the printing process. DI's prepress production section is basically the same as the normal production output. It can accept many prepress software files from Mac or PC, including file formats such as PageMaker, FreedHand, Illustrator, InDesign, CoreIDRAW, and Photoshop. Even explain PDF, Word and other documents. In terms of processing of graphics and image files, it also requires the CMYK format with a resolution of not less than 300 dpi, etc., which is the same as the requirements of a general prepress system.

However, in daily operation, it is necessary to pay attention to the fact that after the plate-making test, there are several small white lines of varying lengths. After careful inspection, it is confirmed that the failure is formed when the document is issued. After careful analysis after repeated trials, it was found that in the process of issuing CoreIDRAW files, “ps3” should be selected for PS file compatibility options, otherwise the EPS diagram in the CoreIDRAW file, the PSD diagram to the bottom, etc., will be easily generated after RIP interpretation. Very thin white line, and the position is not fixed. This is difficult to see in ordinary previews, and can only be discovered after the system is finished or printed, thus causing unnecessary waste.

At present, waterless offset printing inks are Japan's Toyo waterless ink and Germany's K+E waterless ink. After long-term use, these waterless inks are found to have strong hiding power, and yellow ink is inferior to existing ones. Traditionally printed bright and fast-drying inks are bright, so the printed product is not bright and the field density value is high. Therefore, in the production process, we must recalibrate the color, increase the proportion of yellow ink, and select European standards in Photoshop. The total amount of ink is set between 280 and 300. The total amount of ink used in traditional water offset printing is generally set. Between 360-380.

Furthermore, due to the fact that DI uses lasers to ablate image forming systems on silica plates, it is greatly influenced by external factors such as room temperature, the degree of decay of diode laser heads, and the cleanliness of diode laser heads on silicone plates. The reproducibility of small outlets below 8% is not good, especially in the flat screen gradient. 8% or less of the network is disorderly and disorderly, and the transition is not smooth, which seriously affects the quality of printed products. Therefore, it should be avoided during design and production.

After the plate-making is completed and the printing begins, there will be a bad phenomenon of inking on a certain set of silica gel plates, especially on the part of the field and flat net, where ink channels or snowflake-like spots that are vertical to the axial direction, different shades, and through the whole plate appear. . This is mainly due to the fact that the silicon particles in the graphic part have not been cleaned, affecting the ink receptivity of the film base, and manual printing is required, which seriously affects the time efficiency. After careful analysis of the cause of the malfunction, the cleaning device can be withdrawn first, then the screw can be loosened, and the airbag and wash plate bracket can be removed, with 0.1-D. The 3mm-thick waste film base is cut into a Yamagata shape and added under the screws under the plate-washing cloth to increase the pressure at the time of automatic plate-washing. However, the micrometer should be used to carefully measure the thickness of the base film to be added. The pressure should not be too great. Do not exceed O. .9mm to avoid scratching the plate during cleaning. If the plate is still not well inked after the automatic cleaning, it must be manually scrubbed, soaked in alcohol with a degreasing sponge, and wiped in a non-inked area. At the same time, attention must be paid to the nails of the operator and the strength of the plate. Do not wipe it in a straight line to avoid scratching the plate.

At the same time in the daily maintenance should pay attention to several points: In the printing process, sometimes a phenomenon of dirt, dozens of sheets back to normal after careful inspection after shutdown found that the reason is that when the boot cleaning ink, residual cleaning The ink cleaning agent in the tube slowly collects the salty mass and drips into the ink path, instantly changing the printability of the waterless ink, causing a printing failure. Because the DI machine cannot wash the car wash water directly on the ink roller during cleaning, it is added through the injection nozzle outside the machine wall. Therefore, a leather tiger is provided on the machine. When the cleaning is finished, the leather tiger must be used. The injection nozzle is blown to completely remove the residual liquid in the cleaning tube. This process must not be lazily saved, so as not to cause hidden dangers to printing.

At present, whether waterless offset printing can be popularized is the key to solving the problems of waterless offset printing plates and waterless offset printing inks. In particular, the surface of silicone plates is brittle, easily scratched, and has no remedy. Method. At the same time, the problem of dirt on the printing plate, handling problems after the printing plate is dirty, etc. also plague the discretionary control of the printing process. The overall quality of waterless offset inks is not as good as that of conventional water-based offset printing. In addition, waterless offset inks can only be used within a certain temperature range. Therefore, how to solve the problems caused by the use of waterless offset printing inks is a technical problem for ink manufacturers.