Plastic woven bags are now intensifying in the market, but the competition in the woven bag printing market has been fierce. In the future, pp woven bag printing will occupy the entire bag market. First of all, in today's society, only those pp bag manufacturers that can provide good printing quality can win the favor of customers. This requires woven bag printing manufacturers to have an in-depth understanding of the characteristics and use of inks, plates and anilox rolls, and how to effectively improve the quality of the entire printing process.
First part: ink
In the event of print quality problems or failure to meet the required printing standards, ink is the first and foremost object of doubt. In order to obtain good print quality, you need to understand the characteristics and application skills of the ink itself:
1. Viscosity: In the days before the paper bag printing task is planned to start (especially before important and complex printing tasks), the ink modulator needs to undertake the paper bag printing task (printing process, background ink block, overprint combination, etc.) ) The printing speed to be set is fully understood. Only in this way can the ink viscosity be adjusted according to the printing needs.
2. pH value: In addition to paying attention to the viscosity of the ink and all the above related information, the ink modulating personnel also need to determine the correct ink pH value to obtain the best printing effect. It is worth noting that the pH of the aqueous ink will gradually decrease, especially during the printing process or for a long time in the air (without the lid of the ink cartridge). Therefore, when not using ink, cover the ink cartridge cover tightly. Once the pH is lowered, the viscosity of the ink increases. Only when the pH is adjusted back to the standard state (8.2-9.0), the viscosity of the ink can be restored to the normal state. Changes in viscosity during the printing process will not only lead to changes in the printing color, but also may lead to other problems, such as: dirty printing, outer edge band phenomenon, reduced color wear resistance and so on. Therefore, it is useful for automatic ink viscosity or pH adjustment devices designed for high-end users when installed in a printing linkage unit.
3, color: Everyone wants the color of the printed paper bag to meet the customer's requirements. In addition to this, there are some caveats:
For the actual paper bag printing and proofing paper bag printing, the same printing machine/paper must be used. Remember that the digital machine is not available for digital proofing. Because the digital machine is 6 colors and 8 colors, the printed color is very bright, and the printing machine cannot be used with the digital machine. .
Second part: Before using the printing plate, there are several parameter standards that require special attention:
1. Hardness: Appropriate plates must be carefully selected for different printing jobs. Fine print designs include dots, small letters, bar code printing, and require a higher hardness plate, such as 55° shore A; cardboard printing requires a slightly lower hardness for the plate, approximately between 36° and 38° shore A.
2. Sticky paper: The printing plate with too high paper stickiness is easy to cause "dirty" printed products, because dust or other dirt on the substrate is easy to adhere to the printing plate, and in the long run, the printing plate will be carried. The ink capacity is weakened and the printed color density is lowered.
3. Surface tension: Inspecting the surface tension is particularly important for photosensitive resin printing plates, because some processes during the production of such printing plates, such as cleaning and disassembly, may cause changes in the surface tension on the finished printing plates.
4. Cleaning: Whether it is a rubber plate or a photosensitive resin plate, it needs to be thoroughly cleaned. Dry ink agglomerates and cardboard dust adhering to the plates are removed after each use. If it is not cleaned, it will result in reduced print quality, reduced ink transfer capacity, and reduced printing equipment life.
Finally, periodic hardness testing should be performed on the plates, especially after printing 200,000 sheets. Once the hardness of the tactile plate is significantly enhanced or weakened, a new plate needs to be replaced.
Third part: Printing registration accuracy must be very accurate.
1. A good printing equipment should be equipped with a dust collector in the paper feeding section before the first printing unit, because if there is dust on the paperboard, it will have a great influence on the printing process.
2. Cleaning of the printing equipment includes cleaning of each part of the anilox roll, printing roll, correction roll and substrate, which is a prerequisite for better print quality.
In short, in addition to mastering the characteristics and use of inks, plates and anilox rolls, combined with the performance and use of other printing equipment and raw materials, in order to ensure good printing quality. The three key factors to improve the quality of paper bag printing are really crucial.