Answers to the application problems of the most po

2022-08-13
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With the practical application of the alternative product of the powder spraying process - composite offset ink additive in all parts of the country, some results have been achieved in the alternative powder spraying process, and users are satisfied with the whole printing process, the overall (comprehensive) printing quality and the post printing process. On the other hand, according to the feedback information, there are sometimes some problems in ink accumulation blanket. Now this problem is summarized and solved as follows

problem feedback

(1) when printing to about 4000 sheets, ink stacking began to occur, but there were no abnormalities in the ink transfer system and printing plate of the machine

(2) when printing more than 5000 sheets, ink piling occurs, and other aspects are normal

(3) when printing 9000 sheets, everything was normal and there was no ink piling

cause analysis

the main causes of ink stacking are: raw and auxiliary materials, environmental conditions and other factors. The phenomenon of ink piling has certain rules. When problems occur, if we carefully observe its development trend, change progress, the location involved and the degree of damage to the quality of printed matter, we can judge the following conclusions through the phenomenon

1. Clockwise ink stacking

ink stacking roller, printing plate, blanket stacking, and ink stacking from top to bottom can be called "three stacking" phenomenon. It is mainly caused by two single physical properties. One is that the ink itself dries too fast or adds too much dry oil (especially red dry oil), which will not only cause ink scaling, but also cause ink texture to coarsen; Second, the pigment particles in the ink are thicker and heavier

2. Anti clockwise ink stacking

"three piles" phenomenon starts from the ink stacking phenomenon of blanket, which is mainly caused by the correlation of the properties of two substances. One is the surface strength of paper, which is mainly used to detect the mechanical properties of three materials. The other is the viscosity and viscosity of ink. Of course, if the viscosity of ink on the printing machine increases greatly, it is another matter. In the process of this problem, the surface strength of paper is the decisive factor compared with the larger viscosity and viscosity of ink

the ink pile caused by ink emulsification is first affected by the ink on the printing plate and inking roller, and then develops in two directions, up to the ink bucket, down to the blanket, and then transferred to the paper. If the ink emulsification is slight, it will not matter. If the ink emulsification is too serious, it will damage the ink structure and make it impossible to print. However, what is easy to be ignored is the gradual ink emulsification, which is neither slight nor serious. There was no obvious change at first. When the moisture content gradually increased and accumulated to a certain extent, the ink would accumulate on the blanket bit by bit. At the same time, it is gradually transferred from the inking roller to the inking system. The phenomenon is that the ink layer on the inking roller thickens slowly in detecting such impact damage, but it is not enough to affect the ink transfer and transfer. At this time, if you don't pay attention to adjusting the ink balance, make a wrong judgment on the root cause of it, and take improper measures, accidents are easy to happen

as for the problem of ink accumulation blanket caused by powder free ink additives, it needs to be demonstrated to draw appropriate conclusions after the feedback information and relevant data are relatively comprehensive, and the product function improvement is implemented according to the actual situation

two suggestions

(1) remove the residual dust attached to all parts of the printing machine. If powder free ink additives are used, they should be completely removed

(2) change the fountain solution regularly, and thoroughly remove the sediment under the water tank and wash the box. The reverse development in the printing process is not only unique in the "three piles" phenomenon, but also in the fountain solution, but it has not attracted people's attention. In case of problems, the following methods can be used to detect the fountain solution: ① after the fountain solution in the water tank is left standing for 4 hours, the fountain solution in the water tank will be divided into upper, middle and lower layers. ② Mix the fountain solution in the water tank, take out 150ml and pour it into a 200ml glass. After standing for 4 hours, pour out the water in the upper and middle layers first (be careful not to stir the sediment at the bottom), then slowly pour out the water in the lower part, take out the sediment at the bottom, spread it on the glass, dry it for 80% and observe it with a microscope. If there is no microscope, you can also use a 30 times magnifying glass to observe carefully, and you can find the reason

ink problem

low temperature in winter is the external factor of ink thickening. Under the influence of temperature, the thinning and thickening of ink (raw ink) is a physical phenomenon, but the change is the form, not the essence (the basic performance of ink)

the ink is too thick and sticky, but it is best not to adjust its viscosity with diluent or inking oil. Because when users need to mix ink, the total amount of various additives that can be contained in the raw ink produced by the ink manufacturer is limited. If it exceeds the limit, even if it can be used, it will weaken the basic performance of the ink and affect the printing quality. In addition, the viscosity of ink is related to consistency, which refers to its nature rather than its phenomenon. In practice, this is often the case. The ink consistency is large, but the viscosity is small, and its fluidity is still large. Therefore, the ink with high consistency does not necessarily have high viscosity, and the ink with high viscosity does not necessarily have high consistency

the thickening of ink caused by temperature can be solved by the following methods: (1) put the original ink on or next to the radiator to slowly heat it up and gradually return to its original state. (2) In case of emergency, boiled water can be used for external heating. The specific method is to pour the boiled water into the basin, and then put the original barrel (box) of ink in the water, but to prevent the immersion of water vapor, take it out when the water temperature drops to about 27 ℃, open the cover and stir evenly. The temperature of the printing workshop should be maintained at about 27 ℃ in the global delivery of new aircraft

the ink also has thick phenomenon under normal temperature, because the consistency of the ink comprehensively reflects the rheological properties of the ink to a certain extent. If the thickening phenomenon is not caused by external factors, it can be summarized into the following two reasons: first, it is caused by the strong thixotropy in the structure of the original ink, but it can still be used after being stirred and restored to its original state; Second, expired ink or deteriorated ink caused by improper storage cannot be used

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