[Technology] Cracking the printing durability of the printing plate

Decrease in printing durability is a common problem in printing production, which causes a series of problems such as increased consumption of raw materials, increased production costs, and longer production cycles. Therefore, improving the printing durability of printing plates is one of the main means for printing enterprises to improve economic efficiency. There are many reasons for the decline in printing durability. When printing plates are degraded in printing production, printing companies should plan and step by step to strengthen communication between prepress, printing and material supply departments. solve.

Printing process

In the printing production, usually the printing staff first finds that the printing plate's printing durability drops, then the printing staff should base themselves on the reasons for the decline of the printing durability of the printing plate from the printing process.

1. Improper concentration of dampening solution

Improper use of dampening solution may cause a decrease in the printing durability of the printing plate, mainly due to the improper concentration of the dampening solution. In general, printers are accustomed to monitoring the concentration of dampening solution by measuring the pH of the dampening solution. It is believed that as long as the acidity of the dampening solution is not strong, the plate will not corrode. However, the buffer content of some dampening solutions on the market is relatively high, so that even if the dampening solution concentration is too high, the pH value will not change too much, which is likely to cause misjudgment by the printing staff. When the concentration of the fountain solution is too high, it will cause excessive emulsification of the ink, affecting the normal transmission of the ink, destroying the balance of the ink and ink, and causing the printing durability of the printing plate to decrease. When the concentration of dampening solution is too low, in order to avoid dirty on the printing plate, the printing staff will increase the amount of water, which will easily cause excessive moisture in the plate, the paper will be wetted, powder and lint will appear, and the plate will be printed. Accumulation on the blanket, the ink roller and the ink roller accelerates the wear of the printing plate. Therefore, when there is a decrease in the printing durability of the printing plate in the printing production, it is necessary to accurately check the dampening solution concentration. A more versatile and reliable method is to determine whether the concentration of the dampening solution is appropriate by detecting the conductivity of the dampening solution in the water tank. It should be noted that in some places, the water quality is poor, and the impurities and calcium and magnesium ions are relatively high (commonly known as “hard water”). This requires an increase in the water filtration device and the softened water device. The water is first treated and then connected to the water tank.

2. There is a speed difference between the plate cylinder and the blanket cylinder

Ideally, during the printing process, the line speeds of the surface of the plate cylinder and the blanket cylinder should be equal, but in reality the blanket will elastically deform under the action of the printing pressure, resulting in a speed difference between the blanket and the printing plate. The surface of the printing plate is worn, which destroys the original surface structure and adsorption properties of the printing plate, thereby reducing the printing durability of the printing plate. Since the speed difference between the blanket and the printing plate cannot be completely eliminated theoretically, the speed difference can be minimized only by selecting a highly elastic blanket and adjusting the thickness of the gasket. In addition, due to the speed difference between the plate cylinder and the blanket cylinder, the pressure between them becomes larger and larger, and the wear on the printing plate becomes more and more serious, so the pressure between them must be adjusted to an appropriate size.

3. There is a speed difference between the printing plate and the water roller and the ink roller.

There is also a speed difference between the printing plate and the watering roller and the inking roller, which causes wear on the printing plate. According to the method of the above example, first check the elasticity of the rubber on the surface of the water roller and the inking roller, and then adjust the appropriate pressure to reduce the wear of the water roller and the inking roller on the printing plate.

CTP plate making process

If the printer still does not find the reason for the decrease in printing durability after checking the press, the next step is to check if there is a problem with the printed version. At present, most printing companies have used CTP plate making. CTP plate making also raises higher requirements for plate making personnel than traditional plate making while saving production time, improving plate making quality and production efficiency. In the CTP plate making process, the following aspects will affect the printing durability of the printing plate.

1. Laser energy is too low

In the plate making process, if the laser energy of the CTP is lower than the laser energy required for the polymerization reaction of the plate material, the photochemical reaction of the photosensitive layer of the plate material is insufficient, resulting in a decrease in the printing durability of the printing plate. The laser energy required for different brands and models of plates is not the same, and the plate-making personnel need to pay attention to adjustment. In addition, since the CTP is used for a long time, especially when there is more dust in the CTP plate making room, the optical path will be stained, so that the laser energy can not reach the set value, so the plate making staff should regularly check and clean the optical path to ensure the appropriate Laser energy.

2. Preheating temperature is too low

During the pre-heating process, some plate-making personnel are worried that the pre-heating temperature will be lowered when the pre-heating temperature of the C-pre-heating probe fails, and the pre-heating temperature will not reach the temperature. Set value. These will cause the preheating temperature to be low, so that the photosensitive layer of the plate which has undergone photochemical reaction cannot be fixed on the aluminum plate base, resulting in a decrease in printing durability of the printing plate.

3. The developer concentration is too high and the development time is too long

During the development process, if the developer concentration is too high and the development time is too long, the photosensitive layer of the printing plate may be excessively "corroded", so that the printing durability of the printing plate is lowered. Therefore, the plate making personnel must strictly control the developer concentration and development time.

4. Insufficient flushing

In the rinsing process, if the flushing amount is insufficient, the developer on the printing plate may not be completely washed, causing the developer to remain on the printing plate, corroding the photosensitive layer, and causing a decrease in the printing durability. The plate maker needs to carefully check the water outlets of the processor to avoid blockage of the water outlet.

Printing supplies

Printing consumables may also cause a decrease in the printing durability of the printing plate. If there is a quality problem with the plate itself, you can find the problem by comparing it with different presses or CTP. If there is a problem with the ink, it is more troublesome. Because the printing company lacks the means of ink detection, even if the ink is detected by a specialized agency, the ink factor cannot be completely ruled out. This is because the ink used by each printing company has a slight formula. Different, the standard cannot be unified. Generally, after eliminating other factors that may affect the printing durability of the printing plate, the ink manufacturer's technicians can follow the production, and adjust the ink formulation according to the actual production situation to solve the problem of the printing plate's printing durability.