At present, the competition in the paper bag printing market is very fierce. In the future, the enterprises that produce and sell paper bags will face great challenges. Only those who strive to improve the quality of paper bag printing can get more orders and profits.
To improve the quality of paper bags, manufacturers need to have an in-depth understanding of ink, printing skills, knife plates, film mulching, and manual folding of paper bags, to effectively improve the quality of paper bags.
First, ink:
Poor ink is the most important factor that leads to printing quality problems or failure to meet printing standards. If we want to obtain good printing quality, we need to understand the characteristics and application skills of the ink itself.
1.Ink viscosity: before planning to start printing.
Especially before important and complex printing tasks.
Ink modulators need to know the printing tasks to be undertaken (including the printing process, background ink blocks, the combination of overprinting, etc.), as well as the composition of the roller and the printing speed to be set. Adjust the viscosity of the ink according to the printing requirements.
2. The PH value of the ink.
The ink modulator needs to determine the correct PH value of the ink to get the best printing effect. The PH value of water-based inks will gradually decrease, especially when water-based inks are exposed to air for a long time during the printing process or for a long time (without ink tube lid). Therefore, when the ink is not used, the ink cylinder lid should be tightly covered. Once the PH value of the ink decreases, the ink viscosity will increase.
Only set the PH value to the standard state (8.2-9.0), the ink viscosity is the normal state. In the process of paper bag printing, the PH value drives the change of ink viscosity, which will cause the change of printing color, and it may also cause the printing paper to be dirty, the phenomenon of external aid belt and the decrease of color wear resistance.
Therefore, installed in the printing linkage unit, automatic ink viscosity or PH value adjustment device designed for high-end users is very useful.
Ink printed color:
Whether it is paper bag manufacturers, paper bag wholesalers, retailers, all hope that the finished color of the printed paper bag meets the regulations. To achieve a good printing effect, we also need to pay attention to the following three points:
1.The same amount of printing paper must be used in actual printing and proofing printing.
2.Must use the same printing equipment, the same printing speed, parameter settings, plates, rollers, and other parts.
3.The printed color and the standard printing color must be compared under the same lighting conditions.
According to the international laboratory and quality control (QC) report, the color evaluation also includes the color viscosity comparison of the two printing results. That is, if the viscosity of the two printing results is not the same, it is impossible to get the “QC PASSED” label even within the allowable error of the colorimeter.
To keep the ink in good condition after use, and to ensure that the property of the ink is still stable when it is used again a few days later, it is necessary to pay attention to small details:
1.Never add water to the ink to dilute the ink color concentration, especially in the case of high temperature for a long time.
The specified diluent recommended by the ink supplier needs to be used.
2. Warn the operator not to bring too much moisture (excluding the moisture when cleaning the drum) into the ink cylinder each time the printing is finished.
3. Before reloading the ink into the ink drum, each index of the ink needs to be re-determined and adjusted by the international quality control (QC) and quality assurance (QA) system. Including readjusting ink viscosity, PH, and color back to the original standard.
Second, printed plates:
Before using a printing plate, there are several parameter standards that require special attention:
1.The hardness of the printing plate.
According to different printing requirements, select the appropriate hardness of the printing plate. Fine printing design includes dot, small letter, bar code printing, requiring high hardness plates. For example, 55 °shoreA. For cardboard printing, the hardness of the printing plate is slightly lower, about 36 °- 38 °shoreA.
2.Stickiness
The printing plate with too high stickiness is easy to cause “dirty” printing products, because the dust or other dirt on the carrier is easy to adhere to the printing plate, and in the long run, it will lead to weak ink-carrying capacity of the printing plate and decrease of printing color concentration.
3. Surface tension
Surface tension is particularly important for photosensitive resin plates. In the process of making plates, cleaning and disassembly may lead to changes in surface tension on the finished products.
4. Cleaning
Whether it is a rubber printing plate or photosensitive resin printing plate, all need to be thoroughly cleaned. After each use, it is necessary to be clear about the dry ink caking and cardboard dust adhered to the printing plate. If it is not cleaned, the printing quality will be reduced, the ink transferability will be weakened, and the service life of printing equipment will be shortened.
Finally, the hardness of the plate should be tested regularly, especially after printing 200000 sheets, the hardness of the printing plate will be weakened, so it is necessary to replace the new plate.
Third, netting roller:
The requirements for netting rollers are:
1.Usually the roller is installed on a single printing unit.
And rollers with many holes (> 400) can usually be used for fine printing (small characters): a single printing unit (< 200) with fewer holes (< 200) is suitable for printing cardboard: dual printing unit (4-color press) for general printing (number of holes: 200-300).
2. If the packaging manufacturer has the latest generation of printing equipment that can quickly change the screen roller, it can be printed for both long and short periods.
A set of netting rollers with 160-550 holes is enough to meet the printing requirements of corrugated board manufacturers. The roller with 440-1260 holes is suitable for narrow printing.
Fourth, the printing quality of paper bags, but also need to consider the characteristics of the substrate and the use of other equipment.
When the printing quality is poor, many people will blame the poor printing quality on the poor ink, often ignoring the factors of the substrate. Mainly because the characteristics of the substrate are not easy to be observed by the naked eye, not as obvious as the ink (such as how much foam, ink concentration, or whether it is smooth). The qualification of the substrate can only be observed from the color and glossiness of the paper. Before the cardboard is used in printing, many characteristics of the cardboard can be detected through the quality control system (QC).
Several points to note include:
1.Material composition of paperboard.
Fiber distribution characteristics of paperboard/smoothness of paperboard).
2. Air permeability
Water absorption, usually determined by COBBSIZE/FELT).
3. Color and glossiness.
4. Thickness.
5. Surface tension
Low surface tension of paper will make it difficult for water-based inks to color).
6. Paper cleanliness
Dust on the paper surface can seriously affect the printing process).
A substrate with a small hole may cause the ink to dry too quickly, which can easily clog the plate or roller, and even cause wear and tear in serious cases. Printing on a paper surface that is too rough can not achieve good printing quality, because the operator needs to exert more pressure on the substrate to achieve a normal printing effect. Printing on a thicker substrate can achieve better printing results (especially in the color overprinting process).
Dark paper is not easy to get a bright printing effect. To ensure the printing effect of color, it is best to choose high quality, thick, smooth white cow cardboard or ivory whiteboard.
Fifth, the factors that affect the printing quality include:
1.Accurate printing accuracy.
2.A dust collector is arranged on the printing press, which is installed in the feed part of the machine to prevent the dust on the paper from affecting the printing effect.
3.Clean the following parts of the press.
Screen rollers, printing rollers, correction rollers, and each part of the paper printing process. The cleaning of the printing press is a prerequisite to ensuring good printing quality.
In short, to master the characteristics and use skills of ink, printing plate, and screen roller, but also to combine the performance and use skills of other printing equipment and raw materials to ensure good printing quality.
The quality pass rate and production efficiency of paper bag printing need to be improved, which is the problem that all paper bag printing factories continue to solve.
The printing quality and production efficiency of many paper bag printing factories can not keep up with the following reasons: first, the production equipment of paper bag manufacturers is backward; second, the production technology of paper bag manufacturers can not keep up with; third, paper bag manufacturers do not have technological innovation.
How to reverse the poor printing quality and low production efficiency of the paper bag printing factory?
It is necessary to introduce advanced packaging and printing equipment and technological innovation to improve its competitive advantage. Take Wepaperbag as an example, although we started relatively late, we actively introduced international advanced paper bag printing equipment and learned advanced paper bag production technology, so after several years of development, we have become a relatively mature paper bag manufacturer.
Of course, if you need paper bag printing, you are welcome to contact us by email (sale01@wepaperbag.com)!
