With the practical application of compound offset printing ink additives as an alternative product to the powder spraying process in various parts of the country, some achievements have been achieved in the alternative powder spraying process, and the overall printing process and overall (all-round) printing quality and post-printing process have been achieved. At the same time, the effect of satisfying users is achieved. On the other hand, according to the feedback information, there are some problems that sometimes occur when the ink is stacked on the blanket. The problem is summarized and summarized as follows.
(1) When printing to 4000 sheets or so, the phenomenon of stacking began to appear, but no abnormal phenomena occurred in the ink transfer system and plate of the machine.
(2) More than 5,000 copies were printed, ink piled up, and other aspects were normal.
(3) When printing 9,000 sheets, everything was normal and there was no pile-up phenomenon.
The main causes of heaping ink are: raw and auxiliary materials, environmental conditions and other factors. The phenomenon of pile-inking has certain rules. When problems occur, if we carefully observe the development trend, the progress of changes, the locations involved, and the degree of damage to the quality of printed matter, we can determine the following conclusions through phenomena.
1. The clockwise stacking ink roller, the stack printing plate, the pile blanket, and the stacking of ink from top to bottom can be called the "three piles" phenomenon. It is mainly caused by two single physical properties, one is that the ink itself is dried too fast or has added too much dry oil (especially red dry oil), which not only causes the ink crust, but also causes the ink texture to become thicker; The second is that the pigment particles in the ink are thicker and have a heavier texture.
2. Counterclockwise stacking of ink "three heaps" phenomenon began in the pile of ink blanket phenomenon, mainly caused by the correlation of the properties of two substances, one is the surface strength of the paper, the second is the viscosity and viscosity of the ink. Of course, if the viscosity of the ink on the printing press has a large added value, then it is another matter. In the course of this problem, the surface strength of the paper is determined by the surface strength of the paper compared with the larger viscosity and viscosity of the ink.
The ink pile caused by ink emulsification is first affected by the printing plate and the ink on the ink roller, and then it is developed in two directions, up to the ink fountain, down to the blanket and then transferred onto the paper. If the degree of ink emulsification is slight, it will not hinder, and if the ink is emulsified, it will cause a pile of blankets and an ink roller phenomenon. If the ink emulsification is too severe, the structure of the ink will be destroyed, resulting in the inability to print. However, what is easily overlooked is the progressive ink emulsification phenomenon, which is neither minor nor severe. At the beginning, there are no obvious signs of change. When the moisture content becomes larger and accumulates to a certain degree, the ink will accumulate little by little on the blanket. At the same time, the ink roller is gradually transferred to the ink transfer system. The phenomenon is that the ink layer on the ink roller slowly thickens, but it does not reach the extent that affects the ink transfer and transfer. At this point, if you do not pay attention to adjust the balance of ink and water, miscalculate the root causes of the ink, and improper measures, it is prone to accidents.
With regard to the problem of non-powdered ink additives causing the ink to accumulate blankets, the feedback information and related materials need to be comprehensive, and then be demonstrated to draw proper conclusions, and to implement product function improvement according to the actual situation.
(1) Remove any residual dust that adheres to the components of the printing press. If you use powder-free ink additives, it should be completely removed.
(2) Regularly replace the dampening solution while thoroughly removing the sediment under the water tank and scrub the cabinet. The reverse development in the printing process is not only unique to the "three heaps" phenomenon, but it is also found in dampening fluids, but it has not yet attracted people's attention. When encountering problems, the following methods can be used to detect the fountain solution: 1 After the fountain solution in the tank is left to stand for 4 hours, the fountain solution in the tank will be divided into upper, middle and lower layers. 2 Mix the dampening solution in the water tank, and take out 150ml of glass that has been poured into 200ml. After standing for 4 hours, pour the upper and middle layers of water first (be careful not to stir the sediment at the bottom). The lower part of the water was poured out, and the precipitate left on the bottom was taken out and placed on a glass slide. After drying to 80 percent, the microscope was used for observation. If you do not have a microscope, you can use a 30-fold magnifying glass to observe carefully and you can find the reason.
Low winter temperatures are external factors that make the ink thicker. Under the influence of temperature, the thick change of the ink (primary ink) is a physical phenomenon, but the change is the morphology, not the essence (the basic performance of the ink).
The ink is too thick and the viscosity is large, but it is best not to use thinner or varnish to adjust its viscosity. Because when the user needs to mix ink, the total amount of various additives that can be contained by the original ink produced by the ink manufacturer is limited. Exceeding the limit amount, even if it can be used, the basic performance of the ink is weakened and the printing is affected. quality. In addition, the viscosity and the consistency of the ink are related. Here it refers to its properties and not to its phenomenon. In practice, this is often the case. The ink has a large consistency, but its viscosity is small and its fluidity is still large. Therefore, inks with high consistency do not necessarily have high viscosity, and inks with large viscosity do not necessarily have large consistency.
The phenomenon of ink thickening caused by temperature can be solved by the following methods: (1) The original ink is placed on the radiator or next to the heating, so that the temperature rises slowly and gradually returns to the original state. (2) External heating can be performed with boiling water in emergencies. The specific method is to pour boiling water into the basin, and then put the original barrel (box) ink in water, but to prevent water vapor from immersing, until the water temperature drops to around 27 degrees Celsius Take it out, open the lid and stir it to use. The temperature of the printing shop is preferably kept at around 27 degrees Celsius.
The ink is also thick at normal temperatures because the consistency of the ink reflects the rheological properties of the ink to a certain extent. If it is not due to external factors caused by the phenomenon of thickening, can be summarized as the following two reasons: First, due to the strong thixotropy in the original structure of the ink caused by, but after stirring to restore the original state, can still be used; two expired ink or Deterioration inks due to improper storage cannot be used.