Gravure machine operating procedures and precautions for each process
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First, the printing process of plastic gravure printing machine
Film unwinding → tension control → printing first color → drying → overprinting second color → drying → overprinting third color → drying → overprinting fourth color → drying → traction → winding
Second, the operation procedure of plastic gravure printing machine
1, preparation work
1 Check for dust, rubbish, and debris not related to printing around the press, and check that the ventilation and exhaust facilities are intact.
2 Check if the raw and auxiliary materials are adequate and meet the printing requirements. The printing of plastic film requires that the substrate film to be printed meet the following requirements: the surface is smooth and flat, no obvious stiffness, yellow and black spots, holes, and five excessive wrinkles; the average thickness error of the substrate film to be printed should be 10%. Within the (1m printing width), the calculation formula of the average thickness error can be referred to the requirements of the dry composite substrate film; under the printing pressure, the elongation of the substrate to be printed should be within 1%; the substrate film to be printed The surface tension should be ≥40dyn/cm; knowing the affinity between the substrate film and the printing ink in advance, the printing speed and the ink concentration can be larger for the film which is easy to dissolve and swell with the solvent in the printing ink. When printing the coated substrate film coating layer, it is necessary to know how the coating resin adheres to the ink.
3 Check the quality of the plate roll. Note that the set of color plate rolls should be slightly larger than the previous color. For example, the circumference of the second color plate roller should be greater than the first plate roll length of 1%, at least slightly larger or equal, absolutely not smaller than the first color, otherwise it cannot The overprint is correct. Check the plate pattern and color scale.
4 Check whether the printing, feeding, feeding, drying, inking, drawing and winding parts of the printing machine are stuck, the lubricating part is injected with lubricating oil, the oil path is smooth, and the instrument is in good condition. If there is an ink viscosity automatic controller on the device, adjust the viscosity of the printing ink to a set value of 14~18s, and pour the mixed solvent into it, and connect it to the ink tank with the ink pump. Check the computer's automatic version of the device.
5 Match the ink and choose the same color ink as the proof color.
2, installed version
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 roll from being cracked. If it is too loose, it will “escape the plate” when printing. The plate roller is mounted in accordance with the printing color sequence. The printing color sequence printed in the printing is gold and silver ink → black ink → original green → original yellow → original red → white ink. Just the opposite when printing: white ink → magenta ink → yellow ink → green ink → black ink → gold and silver ink.
3, the upper squeegee
The squeegee is generally made of thin steel sheets with a thickness between 0.15 and 0.55 mm. The angle between the squeegee and the tangent point of the contact point of the printing roller is between 15 ° and 45 °, less than 15 °, the ink is not easy to scrape; more than 45 °, the damage to the printing plate and the scraper is relatively heavy, easy to put the printing plate The chrome layer is scratched. The pressure of the doctor blade is not too large, too large, and it is easy to damage the plate; too small. It is not easy to scrape the ink. When the squeegee is used, you can use 280~400 mesh oil stone, evenly oiled from left to right, or use 800° or more metallographic sandpaper to apply oil to remove the squeegee together with the knife holder. The rear clip is evenly ground on the fixture to prevent the blade from injuring people's fingers.
The squeegee overlaps with the hard lining and is placed in the middle of the upper and lower clamping plates and bolted tightly. When operating, the bolts should be screwed symmetrically from the center to the left and right ends to prevent the blades from bending. The length of the razor blade extending from the hard knife lining is 10~20mm, the extension length is too long, the squeegee is soft and not easy to scrape; too short, the rigidity is increased, the scratch is too large, and the knife is damaged. The thickness of the hard knife lining is easily 0.8~1.8mm.
4, boot printing
The gravure rotary machine generally uses an infinitely variable speed system to control the printing speed. In order to synchronize the printing units of each color, a main motor and a continuously variable transmission are used, and the entire printing system is driven by a long rotating shaft. Turn on the ink pump and check if the ink pump is reversed. Start the main motor with each plate clutch disengaged, check the transmission shift, then open the dryer and blower, close the clutch at low speed, and color the sleeve. Taking the first color as a reference, the jog switch is activated to perform the second, third, and fourth longitudinal color registration calibrations; then, the second, third, and fourth color lateral color registrations are still performed based on the first color, and the horizontal direction is The color of the set is fine-tuned with the hand wheel. After the vertical and horizontal color registration, the printing speed is accelerated. If there is no fully automatic computer-to-plate device, the printing speed should not exceed 40m/min, whether it is a satellite rotary machine or a combined rotary machine. More than 40m / min, the naked eye can not track observation, generally controlled at 25 ~ 30m / min. Operators should pay close attention to the color of the case and adjust it manually at any time. If there is a fully automatic computer-to-plate device, the operation mode should be placed on the automatic version. At this time, the computer can automatically track and find the deviation, and automatically send out a correction signal to move the plate or substrate and realign .
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 warming of the substrate facilitates the improvement of the adhesion of the printing ink and drying. After the ink is applied, the ink enters the dryer, and the arrangement of the dryer temperature is set in a low-high-low form for quick drying. It can not be printed to a high degree of drying immediately after printing. This makes it easy to form a film on the surface of the ink layer, and the solvent in the tissue is evaporated and dried. As a result, the printed matter is not dry enough, and it is easy to be anti-sticky during stacking.
The printing substrate has different tension control. For the BOPP film, the tension control per meter width is preferably 5~8kgf (49~78.4N), the printing tension of the biaxially stretched nylon film is controlled at 78.4~98N, and the printing tension of the biaxially stretched PET film. The control is at 98~117.6N. If it is less than 1 meter wide, multiply the ratio of its width to 1m, such as 0.7m. Then the above tension is multiplied by 0.7. When the nylon film that has been absorbed is printed, the ink adhesion is lowered and the printing edge is overflowed. In this case, the first color dryer can be opened, and the first color plate roller can be placed in the second. At the color position, each color moves back one unit. The first color becomes the dry position of the nylon film, and the drying temperature can be set at 80 to 90 °C.
5, work after the end of printing
After the printing task is completed, the main motor is stopped, and the printing substrate stops feeding. The embossing roller is lifted, the squeegee is separated from the printing plate, the ink pump is stopped, the remaining ink is poured out, the surface of the printing plate is cleaned until there is no residual ink, the printed substrate is removed, the dryer is turned off, and the ground is cleaned. When the plate is no longer in use, remove the plate, erect both ends, and place it on a dedicated plate holder. If you don't use it for a long time, pack it in the warehouse. A set of rollers should be placed together to avoid clutter, labelled on the outside, and indicate how many impressions have been printed for ready use.