Film gravure printing all-sealing

[Chinese Packaging Network News] In the process of film gravure, dirty faults occur from time to time. There are many reasons for the occurrence of irregular dirty faults. This article makes a detailed analysis of irregular dingling faults from gravure cylinder making, squeegee selection and installation, ink and dilution solvent, workshop environment and production operation.

First, gravure cylinder production

1、Cause analysis

(1) If the hardness of the chromium plating layer on the intaglio cylinder surface does not meet the minimum requirements, the non-graphic area of ​​the intaglio cylinder surface will easily cause excessive wear and friction with the blade, and the worn area will be immersed in the ink during use. , and thus transferred to the film to produce dirty faults.

(2) If the gravure cylinder is not sufficiently polished after chrome plating, it will cause the surface of the chrome plating layer to be rough, and it will cause dirt problems when the machine is used.

(3) There is a plate-making defect in the gravure cylinder, which may cause ink marks to remain, resulting in a dirt failure.

2. Countermeasures

(1) Ensure that the gravure cylinder has a smooth surface, high hardness, good wear resistance and long service life.

(2) Integrate the hardness of the intaglio cylinder, the depth of the cell depth, and the distribution of the cell sites to determine the maximum capacity of each intaglio cylinder. Once this value is exceeded, the surface of the intaglio cylinder needs to be chrome-plated.

(3) Prior to formal printing, the gravure cylinder surface must be grinded in all directions with 800# to 1000# sandpaper.

Second, scraper selection and installation

1、Cause analysis

(1) scraper hardness discomfort.

(2) Incorrect blade installation method, insufficient blade pressure, improper angle between the blade and the intaglio cylinder, insufficient blade grinding, or improper distance between the blade scraping point and the ink transfer point.

2. Countermeasures

(1) Select a self-grinding scraper with a tight material and moderate hardness.

(2) Ensure that the scraper is installed correctly and the force is evenly distributed. The lining knife (also called “sub-knife”) generally chooses a corrosion-resistant flat steel plate with a thickness of 0.5 mm. The installation position should be 15 to 20 mm beyond the tool holder jaw, and the scraper position should be Beyond the top of the lining blade 3 to 5mm. The angle between the doctor blade and the intaglio cylinder should be 55° to 60° and tilt up.

(3) During the operation of the equipment, the swing amplitude of the scraper should be 5~10mm, and the swing period should be 2~5s.

(4) Before the official printing, the scraper must be fully ground with 1000 # sandpaper.

(5) According to the drying speed of the ink, set a reasonable distance between the scraper blade and the ink transfer point.

(6) For non-scratched inks in non-graphics areas, by appropriately reducing the speed of the equipment, adding a blower tube in the non-graphic area of ​​the gravure cylinder, adding anti-adhesion aids in proportion to the ink, or not causing plugging In the case of failure, appropriate measures such as quick-drying solvents should be added to make the ink dry in time so as not to transfer the dirt to the surface of the film.

Third, ink and dilution solvent

1、Cause analysis

(1) The particles of the resin binder and the pigment in the ink are too large, so that they cannot be fully dissolved by the diluting solvent, so that a large number of particles are accumulated at the edge of the knife. Although the squeegee blade can grind and disperse these particles, it still remains in the intaglio cylinder. The ink and traces are left in the graphics area, causing dirt problems.

(2) The ink viscosity is too high, resulting in a deeper abrasion between the gravure roll and the doctor blade, which in turn causes a dirty problem.

(3) Dilution ink dilute solvents are mostly mixed solvents. During the high-speed operation of equipment, the quick-drying solvent will volatilize in a large amount. The slow-drying solvent will gradually accumulate in the ink tank, even if new dilution solvents are continuously added for adjustment. The equilibrium ratio of the mixed solvent is also changing, resulting in the ink drying slowly, the solubility is weakened, and the ink scraping effect is deteriorated, so that residual ink marks are transferred to the film surface and dirt problems occur.

2. Countermeasures

(1) Using a diluting solvent with a relatively high dissolving power, place a magnetic dispersion rod in the ink tank, add an antistatic agent when necessary, and require the ink manufacturer to finely process the ink. Different manufacturers' inks cannot be mixed.

(2) For different colors of ink, use the filter of the corresponding mesh to filter. In addition, an 80- to 100-mesh filter is installed in the circulation inking apparatus, and the ink returned from the ink tank is filtered by the filter before printing.

(3) Use ink with shorter storage time to reduce the residence time of the ink in the ink tray and the recirculating ink transfer device. For the ink with a retention time of more than two hours, the filter should be re-used with a filter of more than 150 mesh and be adjusted to normal. Use viscosity while stirring well to make the ink have good solubility.

(4) The viscosity of spot colors and monochrome inks should be moderate, and the stability of the ink viscosity in the gravure printing process should be ensured. The commonly used benzene-free and non-ketone inks have higher viscosity requirements. In order to stabilize the ink viscosity, the ink viscosity should be tested every half hour, and the dilution solvent should be added in time.

(5) The remaining ink is reused by adding new ink, and the mixing ratio of the new ink and the old ink is determined according to the ink storage time so that the ink can be fully dissolved.

Fourth, the workshop environment

1、Cause analysis

Improper temperature and humidity in the workshop and poor cleanliness of the air may all cause dirtying.

(1) The temperature of the production shop is too high, the evaporation rate of the diluting solvent and the drying speed of the ink will be accelerated. If it fails to adjust in time, the viscosity of the ink will increase, which will result in difficulty in scraping the ink, and it will not only damage the gravure cylinder and the scraper, Dirty faults will also occur.

(2) If the humidity in the production room is too high, the solubility of the ink will deteriorate, causing the ink particles to aggregate and cause dirt problems.

(3) There is more dust in the air of the production workshop. If the equipment is not cleaned regularly, the dust is easily adsorbed on the surface of the film under the action of static electricity, and is transferred to the surface of the gravure cylinder during printing, or is accumulated in the ink. As a result, there is a dirty fault.

2. Countermeasures

The temperature of the production workshop should be controlled at 18 to 28°C as much as possible, and the humidity should be controlled at 45% to 75%. At the same time, the seal of the gravure production environment should be maintained. The air filtration system should be installed so that the production workshop can maintain a positive pressure environment. At the same time, pay attention to the regular cleaning of the equipment, especially around the ink tank, it is best to clean it once a day.

Analysis of Film Gravure Dirty and Countermeasures

V. Production operation

1、Cause analysis

Improper production operations can also cause dirt problems, such as pre-preparation work and improper equipment debugging.

2. Countermeasures

(1) The film gravure printing enterprises should do a good job in prepress preparation, and include the requirements for installation, adjustment, and ink preparation of equipment cleaning, gravure cylinders and doctor blades in daily operation procedures, and operators should strictly implement them.

(2) When the non-image area of ​​the gravure cylinder is immersed in ink due to improper operation, the speed of the equipment is increased to about 150m/min, the scraper pressure is adjusted to a normal state, and then the two are kept running for about 5 minutes. Make sure that it does not cause a dirty problem before printing.

(3) When the stoppage time exceeds 20 minutes, the scraper and the gravure cylinder surface should be kept in a disengaged state to reduce the abrasion of the scraper and the gravure cylinder. When the machine is turned on again, the two must be fully ground and cleaned.