Common gravure product quality problems and solutions

The factors affecting the Printing quality of plastic films include various aspects such as film materials, inks, plate making equipment, and process technology. Printing a product is also related to the use of solvents, ambient air temperature, hot air, and temperature. If on one hand it is not properly considered, there will be quality problems in the printing process. The main ones are the following:
1. Overprinting is not allowed (1) Cause of equipment During the long-term production process, some of the main components of the equipment are worn, such as boring heads are not installed, the printing shaft is bent, the teeth are worn, the sleeve shaft is not refueled, damage is caused, and the pulling roller is not equal. It will affect overprinting.
(2) The printing pressure of each printing roller is uneven, the pressure at the left and right ends of the printing plate is uneven, the printing roller is loose and other factors cause overprinting.
(3) In terms of process technology, the tension control of opening and rewinding is unbalanced, the operation is erroneous, and the heat of the wind is not appropriate. Misalignment and other effects of overprinting are not allowed.
(4) Inaccurate overprinting of each set of specifications (over normal error range) caused overprinting.
(5) The viscosity of the ink is too large to affect overprinting.
(6) Changes in film properties (thickness and unevenness) affect the constant tension, resulting in inaccurate overprinting.
(7) In terms of subjective factors, the printing operation must be strong, the ideology must be concentrated, and the operation must be carefully performed to check the quality of the product, identify the problem in time, and solve the problem.
2. Ink adhesion (1) Solvent problems Due to the improper proportioning of the solvent, the volatilization is too slow, and the solvent contains a small amount of high boiling substances such as cyclohexanone, butanol, etc., and the resin has poor release properties to the solvent.
(2) The drying device of the equipment is insufficient in the amount of hot air, improper use of hot and cold air, and fast speed.
(3) The gravure roll depth in the plate making process is too deep.
(4) The ink is too thick and the ink contains too much plasticizer.
(5) The traction roller is pulled too tight and the winding tension is too large.
(6) Films The additives contained in the film are soluble to the solvent and affect the solvent release. The corona treatment did not or did not achieve the desired surface tension index.
(7) Ink adhesion is caused by environmental factors such as excessive air temperature, humid air, and excessive pressure.
3. Incomplete pattern lines (1) The ink dries too quickly, resulting in a dry print.
(2) The wind and heat are too large, which affects the drying of the concave surface of the printing roller.
(3) The etching of the plate is too shallow and the adhesion of the ink is low.
(4) The pressure of the printing roller and the embossing roller is too light.
(5) The distance between the squeegee on the printing roller and the embossing point is too far (drum type reverse squeegee is easy to dry).
(6) The speed is too slow.
4. Line Marks (1) Squeegee blades have hard particles and impurities on the surface of the printing roller. They must be removed in time. Any unfixed line marks can be sharpened or changed.
(2) If the lines are fixed, there may be hard impurities embedded in the printing roller outlets, which must be removed by parking.
(3) When the new roll was started printing, it was found that the fixed line mark was generally caused by the chrome plating of the printing roll after the napped surface was not smoothed or repaired.
(4) The resin and pigment in the ink are not ground, and it will also cause line marks. It is necessary to use a copper wire brush to remove the impurities in the dot and print it after filtering with 120 copper wire mesh.
(5) Scraper angle, position, hardness, thickness, etc. must be properly adjusted.
There are many factors affecting product quality in the process of plastic gravure web printing. Only in the printing practice, the actual situation of raw materials and raw materials will be explored and solved. (Chen Changjie) ("China Packaging Newspaper and Print Weekly")