The carton is not high-grade, it depends on the printing process is not properly controlled.
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The reason why high-grade watermark cartons are favored and recognized by carton enterprises and customers is that the printing effect is comparable to that of offset carton, with high compressive strength, high production efficiency and high utilization rate of raw materials. In the production process of high-grade watermark carton, the process control of ink printing is regarded as the core link, especially the establishment and realization of the standardized management of ink printing process, which is the most important part of the high-end watermark carton ink printing process management.
Ink printing process control and standardization, according to the principle of ink printing and the conditions of the enterprise, combined with the characteristics of ink printing process, the process elements, process parameters, process documents, etc., to develop a unified process control, and standardize and standardize. The significance is that, first, it can standardize and guide operations, simplify production, guide production, effectively improve production efficiency and process technology level, and reduce labor intensity; second, it can control the process data in accordance with certain standards. Improve and stabilize print quality. In this paper, the author will introduce the process control and standardization of high-grade watermark carton ink printing in combination with the actual situation of our company.
High-grade watermark carton ink printing process control standardization specific details
1. The plate number is verified clearly
The high-grade watermark carton ink printing has a higher number of anilox lines, generally 650 lpi, and the number of printing plates is 120 lpi. The screen printing lines used by the anilox rolls of different network cables are different. Therefore, after the trial production of the products is finished, the printing plates need to be numbered, so that the information such as the number of printing plates is correct when printing each batch, so as to ensure the printing effect. . Finally, the printed products need to be signed by the quality inspector before they can be officially printed.
2. Comprehensive arrangement of color sequence
(1) The color sequence is arranged according to the overprinting effect (ink surface tension). The surface tension of the latter color ink is lower than that of the previous color set. When the overprinting effect is poor, the color sequence can be replaced to reduce the surface tension of the ink of the latter color group.
(2) Arrange the color sequence according to the ink hiding power. The opacity of the first print, the cover power from strong to weak in order is black > blue > red > yellow, otherwise the printing is not true.
(3) Arrange the color sequence according to the dry condition. After drying the slow high opacity ink, the color group should not arrange a large area of light ink. The distance between the two sets of ink must be opened when the drying is turned on. Otherwise, the return shadow is serious, and the return position is the plate cylinder. It is different from the circumference of the anilox roller.
(4) Highlight which color to print first (as opposed to offset color order). For example, when printing a green graphic, if you want to make the color of the picture blue, you can use the blue-yellow order.
3. Ink viscosity, pH index control
(1) Ink viscosity: Ink viscosity coating 4# cup test should be guaranteed between 15 and 20 seconds. If it is too low, the ink will have a large fluidity and the ink will be light; if it is too high, the fluidity will be poor, and the ink will be blocked. Adjust the viscosity of the ink by using thickeners, thinners, thinners and other auxiliary materials.
(2) Ink pH: The pH of the ink should be between 8.5 and 9.5. If it is too high, the ink will dry too slowly, and it will be easy to pull flowers and scum. If it is too low, the ink will dry too fast, which will easily cause dry plates. Stabilizing fluid is required to adjust the pH of the ink.
(3) The ink viscosity is inversely related to the pH value. Figure 2 is a plot of pH versus viscosity plotted on the measured data.
4. varnish performance index control and use precautions
(1) The varnish viscosity coating 4# cup measurement is guaranteed to be more than 25 seconds, and the varnish solid content is guaranteed to be 35% to 40%. If the varnish is too thick, the mixture of alcohol and water should be added slowly. The ratio of alcohol to water is 1:1. If the varnish is too thin, it should be added to the original barrel varnish.
(2) Varnish consumption: 3.5～4.5g/m2 to ensure the rubbing resistance and gloss of the printed products.
(3) The initial drying time of varnish: the surface drying time should not exceed 10 to 15 seconds. Wipe gently with your thumb without clear scratches. To dry and dry at low temperature and low humidity, slowly add 10% mixture of alcohol and water. The ratio of alcohol to water is 1:1.
(4) Replacement and cleaning of varnish: varnish should be replaced immediately after it becomes dirty, impurities and cross-color. The varnish will become dirty and unclean after using the unit time. When printing delicate dots such as dots, it is necessary to replace the new varnish to avoid the transfer of fine impurities in the dirty varnish to the substrate through the anilox roller. The picture caused scratches and filth. On the other hand, once the varnish is cross-colored, the surface of the printed product will have a blooming effect on the surface after calendering.
(5) varnish radius: If the varnish particles are rough, it is easy to drag the last set of ink color of the printed product, resulting in deformation of the dot; if the varnish is too delicate, it will easily lead to poor paper slippage and slippage.
(6) Drying of varnish: If the varnish is dried too slowly, the protection effect on the ink film is reduced; if the varnish is dried too fast, the anilox roll mesh will be blocked. In winter, the temperature and humidity are low and windy. It is necessary to add 10% mixture of alcohol and water to the varnish, the ratio of which is 1:1.
(7) Waterproofing of varnish: Varnish should prevent the corrugated box from absorbing moisture from the environment. If the varnish is poor in water repellency, it tends to cause the corrugated box surface to adhere to the surface and damage the ink film. Print waterproof and anti-stick tests are required before official printing.
5. Printing pressure control
For pressure-reducing printing, the pressure gap between the printing plate of the large ink color group and the varnish group and the embossing roller shall not be less than 2.0 mm. In order to ensure stable printing pressure control, new cardboard printing should not be used. This is because the moisture of the new cardboard is not completely evaporated, and the water is not in equilibrium. If the printing is started immediately, the pressure cannot be controlled and the corrugation is easily crushed. Reduce the strength of the carton. After testing, the gap value varies from 2.5mm to 2.0mm, and the compressive value can be reduced by 500N.
6. Production cycle control
Adjust the storage time of the paperboard according to the change of temperature and humidity in the workshop environment, and ensure that the water content of the paperboard and the surface temperature are suitable before printing.
For low temperature and low humidity, the cardboard should be stagnant for at least 5 hours, after the surface temperature of the paperboard is lowered, but still slightly warmer (the surface temperature of the cardboard is 20-25 °C), and the water content is guaranteed to be between 4% and 7%. Printable.
For high temperature and high humidity, the paperboard should be stagnant for 5-8 hours. After the surface temperature of the paperboard is lowered, the temperature should not be too high (the surface temperature of the paperboard is 20-25 °C), the printing is most ideal.
It is worth noting that the new paperboard has a certain temperature and the moisture does not completely evaporate. If it is put into printing immediately, the printing will be partially faint. Moreover, the ink temperature will increase with the circulation of the ink, resulting in faster drying, printing dry plate, changing the ink characteristics, and it is difficult to ensure the printing color for the corrugated carton products which are more demanding, and the number of stop wiping is increased. To put it another way, when the ink drying speed is too slow, the solution can also be considered from the direction of the temperature of the cardboard. Therefore, to ensure the quality of printing, the production cycle must be determined.
7. Printing quality control
During the printing process, sampling inspections are always carried out, paying attention to printing quality problems, such as rules, overprinting, and hue accuracy. If you encounter quality problems such as dry plate, napping, smudging, and printing, you must deal with them in time.
8. Ink adjuvant addition control amount
The ink adjuvant should be added in an appropriate amount, and excessive moisture should not be added, thereby destroying the printing suitability of the ink and reducing the color saturation. Under normal circumstances, the stabilizer should not be added more than 5%, the slow-drying agent should not exceed 3%, the leveling agent should not exceed 3%, the defoaming agent should not exceed 0.5%, the thinner should not exceed 50%, and the water should not exceed 10%.
9. Watermark room internal temperature and humidity control
The reasonable range of temperature and humidity of the ink printing environment is: temperature 20 ° C ~ 25 ° C, humidity 35% ~ 45%. Printing temperature and humidity have a direct impact on ink properties. Because the paper fiber is a hydrophilic substance, the corrugated cardboard absorbs moisture under high humidity conditions, causing the moisture of the corrugated cardboard to rise and the stiffness to decrease. At this time, pressure printing is required, and printing is easy to be falsified.
If printing at a high temperature of 30 ° C or higher, the viscosity of the ink will decrease, the fluidity will increase, and the scraping of the doctor blade will result in a large area of ink leakage, thereby contaminating the printed product. High temperatures also accelerate the drying of inks and varnishes, causing print quality problems such as dry plates and pastes.
When printing at a lower temperature below 15 ° C, the ink will become thicker, and the printing will become slower, resulting in poor overprinting effect, ink smearing and the like.
10. Ink formulation and process control
The ink is formulated according to the color reduction method, and inks of different manufacturers and different properties must not be used. Old inks formulated with a variety of primary inks shall not be used with spot color inks. When changing the color sequence, the device should be cleaned. When diluting the ink color, do not add water at will, destroying the ink properties; when deepening the ink color, the original color ink should be added.
11. Drying light control
The drying lamp ensures that the initial drying time of the ink and varnish is about 10 seconds. Under normal circumstances, the cardboard contains a certain amount of water, and the surface time of the water-based varnish and ink is 15 to 20 seconds. After the drying lamp is turned on, the drying time can be shortened by half. Therefore, the drying lamp must be turned on during the printing of the ink.
Support document record
In order to achieve standardized management of high-end watermark carton ink printing process, a lot of sound content is needed. Such as "Quality Examination Rules", "Printing Quality Standards" and "Process Index Control Record", in addition to avoiding the quality problems of semi-finished products, it is also possible to analyze, measure and evaluate the level of each process index, and to trace and prevent The role of the premise; "post responsibility system", the specific division of labor, clear the duties and authority of the watermarker's various positions and personnel; "safe operating procedures", that is, the operating procedures, that is, the sequence of steps to operate the watermarker, can help employees understand What time to do, to ensure that production can be carried out safely, stably and efficiently.
High-end watermark carton ink printing process control and standardization is a continuous improvement process. It is necessary to combine various key control points of the entire ink printing process to formulate relevant process instructions, operation specifications, quality standards, etc., and requires process managers and Producers are persistently and strictly implemented to be able to print high-quality, high-end effects.