Gravure printing machine operation procedures and precautions, keep in mind! 2
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Second, the operation of plastic gravure printing machine
1. Preparation
1 Check if there is dust, garbage, and debris that are not related to printing around the printer. Check if the ventilation and exhaust facilities are in good condition.
2 Check whether the raw and auxiliary materials are adequate and whether they meet the printing requirements. The printing of plastic film requires that the substrate film to be printed meets the following requirements: smooth surface, no obvious deadlock, yellow and black spots, holes, five folds; the average thickness error of the substrate film to be printed should be 10% Within the range of 1m (print width), the average thickness error calculation formula can refer to the requirements of dry composite substrate film; under the printing pressure, the elongation of the substrate film to be printed should be within 1%; the substrate film to be printed The surface tension should be ≥ 40dyn/cm; the affinity between the substrate film and the printing ink should be known in advance, and the printing speed and ink concentration can be larger for the film that is easy to dissolve and swell with the solvent in the printing ink. When printing a coating layer of a coated substrate film, it is necessary to understand the adhesion of the coating resin to the ink.
3 check the quality of the roller. Note that the later color plate roller should be slightly larger than the previous color. For example, the circumference of the second color roller should be greater than 1% of the first roller surface, at least slightly larger or equal. It must not be smaller than the first color. Overprinting is correct. Check the roll pattern and color scale.
4 Check whether the printing machine is sending, feeding, moving, drying, inking, traction and take-up. Check if there is any jamming. Lubricate the part and inject the lubricating oil. The oil path is smooth and the instrument is in good condition. If the device has an ink viscosity automatic control device, the viscosity of the printing ink should be adjusted to a set value of 14 to 18 seconds, and the mixed solvent is poured thereinto to be connected to the ink tank with an ink pump. Check the computer to automatically match the device.
5 to deploy a good ink, select the same color with the proof color ink.
2, loading
When loading the plate, pay attention to the left and right sides of the plate. When tightening the cone, do not overtighten it to prevent the copper plate from bursting and loose. When printing, it will “run away”. Install the plate roller according to the printing sequence. The printed color sequence in the printing is gold and silver ink → black ink → original blue → original yellow → original red → white ink. When printed, it is exactly the opposite: white ink → magenta ink → yellow ink → blue ink → black ink → gold and silver ink.
3, upper squeegee
The squeegee is usually made of thin steel sheet with a thickness of 0.15~0.55mm. The angle between the squeegee and the tangent line of the contact point of the printing roller is between 15°~45°, less than 15°, the ink is not easy to scrape; more than 45°, the damage of the printing plate and the scraper is heavy, and the printing plate is easy to handle Chrome layer scratches. Squeegee pressure is not too large, too large, easy to damage the printing plate; too small. It is not easy to clean the ink. When the squeegee knife is used, you can use 280~400 mesh Whetstone to grind evenly with the engine oil from left to right, or remove the squeegee together with the knife holder with 800 mesh or more of metallographic sandpaper. Grip evenly on the fixture to prevent the scraper from damaging human fingers.
The squeegee and the hard lining are overlapped and placed in the middle of the upper and lower clamping plates, and bolted tightly. During operation, the bolt must be symmetrically tightened from the middle to the left and right to prevent the blade from bending. The length of the squeegee blade extending from the hard knife lining is 10~20mm, and the length of the squeegee lining is too long. The squeegee blade is soft and not easy to scrape. When the squeegee is too short, the rigidity is increased, the scratch is too large, and the damage is easily damaged. Hard knife liner thickness is easily 0.8 ~ 1.8mm.
4, boot printing
Gravure rotary machines generally use an infinitely variable transmission system to control the printing speed. In order to synchronize the printing units of different colors, a main motor and a continuously variable transmission are used to drive the entire printing system with a long rotary shaft. Turn on the ink pump and check if the ink pump is reversed. The main motor is started under the state in which the various printing plate clutches are disengaged, the transmission is checked for transmission speed changes, and then the dryer and the blower are turned on, and the clutch is closed at a low speed to carry out color registration. Using the first color as a reference, the jog switch is activated to perform the second, third, and fourth longitudinal trap calibration; the second, third, and fourth colors are then horizontally aligned and horizontally aligned with the first color. The color registration is fine-tuned with the hand wheel. Vertical and horizontal alignment, speed up the printing speed. If there is no automatic computer to the device, the printing speed should be no more than 40m/min whether it is a satellite type rotary machine or a combined type rotary printer. More than 40m/min, the naked eye can not follow the observation, generally controlled at 25 ~ 30m/min can be. Operators should pay close attention to color registration and adjust it manually at any time. If there is a fully-automatic computer-to-printer device, the operation mode should be applied to the automatic registration. In this case, the computer can automatically track and find the deviation, and it will automatically issue a correction signal to move the platen roller or substrate and realign it. .
On the imported equipment, there is a heating roller. After the substrate to be printed is unwound, the substrate can be heated to about 50° C. and then enter the first color printing unit. The warmth of the substrate facilitates the increase of adhesion and drying of the printing ink. After the ink is applied, the ink enters the dryer. The dryer temperature is set in a low-high-low format for quick drying. Can not be printed immediately after the highly dry, so easy to make the surface of the ink layer formed a layer of film, the solvent evaporation inside the organization to dry, the results of the printed matter is not dry enough, stacked anti-adhesion.
Different tension control of the printed substrate is different. For BOPP film, the tension control per width of rice is set at 5~8kgf (49~78.4N), the printing tension of biaxially stretched nylon film is controlled at 78.4~98N, and the printing tension of biaxially stretched PET film Control at 98~117.6N. If it is less than 1 meter wide, multiply it by the ratio of its width to 1m, such as 0.7m. The above tension can be multiplied by 0.7. When printing a nylon film that has absorbed hygroscopicity, there is a phenomenon that the ink adhesion is reduced and the printing edge overflows. In this case, the first color dryer can be opened, and the first color plate roller is placed second. In the color position, one unit is shifted behind each color. The first color becomes the drying position of the nylon film, and the drying temperature can be set at 80~90°C.
5. Work after printing
After the print job is completed, the main motor is stopped and the printing substrate stops feeding. The embossing roller lifts, the blade leaves the printing plate, stops the ink pump, pours out the remaining ink, cleans the surface of the printing plate until no residual ink is present, removes the printed substrate, closes the dryer for electric heating, and cleans the floor. When the plate is no longer in use, the plate is removed, the two ends are set up, and placed on a dedicated plate holder. If you do not use it for a long time, pack it in a warehouse. A group of printing rollers should be put together, to avoid confusion, to be labeled on the outside, and indicate how many impressions have been printed so that they can be used at any time.