Application of zinc oxide plate in printing indust

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Talking about the application of zinc oxide plate in the printing industry and the problems that should be paid attention to

speaking of the beginning of the application of zinc oxide plate, we should go back to the late 1980s and early 1990s, when it was the transition period from letterpress printing to offset lithography printing. In addition, the universal application of computers at that time set off a revolution from "water and fire" to "light and electricity" in the printing industry. In this environment, printing plates used with computers have emerged. One is PS version, and the other is zinc oxide version

the zinc oxide version originally used has many sizes and models. Commonly used are: split, four open and eight open. Folio plates are used in 08 and 01 offset presses. Because the previous edition is simple and suitable for short edition printing, it is deeply welcomed by the printing units of various organs across the country. Quarto offset printing machine also has zinc oxide version, but not too many. Octavo offset press should be the most widely used. We have carried out experiments on the octavo offset press. A good octave plate can generally print 10000 to 20000 sheets under the condition that the pressure and ink adjustment are appropriate to tighten the belt. We have recorded that when the largest piece of zinc oxide letterhead was printed, the plate was still intact when the printing sheet reached 24000

the conditions for the initial use of the zinc oxide plate are limited. Even the fountain solution of the zinc oxide plate must be matched by itself. Four kinds of powders and one kind of glycerin need to be purchased from the pharmaceutical dangerous goods store. At that time, each printing manufacturer had a balance to match and weigh the bought powders. When there is a dirty version in printing, add more citric acid to the potion when matching the fountain solution. In order to promote the use of folio zinc oxide plates throughout the country, some manufacturers, such as the manufacturer of 01 offset press, specially make and provide supporting plate clips. Because the manufacturer of 08 offset press did not provide such plate clips, the text printing units all over the country transformed themselves, or imitated each other, and quickly promoted them

but with the passage of time, zinc oxide is not suitable for the open plate on 08 offset press and 01 offset press, and then it is gradually eliminated by the market. The main reasons are:

⑴ the plate has too strict requirements on the dry and humidity of the climate, and the plate will wrinkle in the printing process if there is any discomfort. The reason is that the components made of tepex can pass the updated and more rigorous collision test experiment, which shows the printing quality problem

⑵ the produced plate will also wrinkle immediately. As the plate is made by photography, the carbon powder is hung on the plate and then solidified on the plate at high temperature, resulting in the loss of water and the reduction of balance after the plate is baked at high temperature. Pleating caused by immediate printing cannot be used

⑶ the size and area of the folio plate are too large, and it is easy to wrinkle after being pressed by the printing machine

⑷ because the plate is paper, after a period of printing, due to the erosion of the liquid medicine on the plate, plus the pressure of the machine itself, as well as the impact and pressure of the water roller and the ink roller on the plate, the plate lengthening has the problem of uneven positive and negative alignment of the printing paper

for the above reasons, the author has taken many methods:

⑴ before plate making, put the plate in a separate room, put a few pots of water on the ground, hang the plate above the basin, and humidify the plate

⑵ after plate making, put the plate in a sealed room, and then hang the plate for humidification. If there is no humidifier and the conditions are limited, the unit will pull the rope in the bathroom and hang the plate for cold plate treatment

⑶ cut the rear part of the plate into a dovetail groove with a length of 10 ~ 20cm and a bottom width of 2cm. Fold the plate itself and drive it out of the dovetail groove at the back of the printing plate together with the machine pressure and the pressure sensing of the ink roller, so as to achieve the effect that the plate does not wrinkle

after the above methods were tested, the above problems were still not solved, so the major printing units stopped using this kind of plate one after another. There are not many applications of zinc oxide plates in four offset press, and they are basically not used now

octavo zinc oxide small offset press, which has been widely used and has strong stability, 1800, 450, 3445 and a3+500 of horizontal feeding paper produced now, have been widely welcomed by printing manufacturers because of its simple version, fast printing speed and stable plate performance

features of octave offset press:

⑴ the machine drum is small, and the layout of zinc oxide plate is relatively small, which provides favorable conditions for the tensile properties of plate. The erosion and elongation of potion will not be as big as that of folio plate

⑵ plate making is simple, and there is no need for a large photographic plate making machine and a large electric oven to fix the plate. When making plates with a copier, you can add a small fixing machine

⑶ the current fountain solution does not need to be prepared by yourself. You can buy finished medicinal powder at any time at the printing material store, and then you can use it after you prepare water in proportion

⑷ the fountain solution prepared by zinc oxide plate powder can be used for PS plate printing (Note: PS plate fountain solution zinc oxide plate cannot be used during printing)

due to its convenience and rapidity, zinc oxide plates have always been popular on octavo offset presses. The form of paper feeding, whether horizontal or vertical, has been widely praised by the printing industry

in the past 20 years, the author's unit has used zinc oxide plates in many octave offset presses, and some conclusions have been drawn in production practice:

⑴ ink problem. Some manufacturers use a barrel of ink for many machines. When cleaning the machine, the fountain solution used for printing with other plates, such as PS plate printing electro-hydraulic servo universal experimental machine, a high-precision experimental instrument combining light, machine and electricity, is recycled into the ink barrel through the unused ink. At this time, if the ink with PS plate fountain solution is used and then used for zinc oxide plate printing, the two fountain solutions are mixed, resulting in chemical reaction, and it is easy to dirty the plate. It is recommended to use the octavo offset press of zinc oxide version "for one ink only", and do not mix multiple machines

⑵ in summer, the temperature is relatively high, resulting in high ink fluidity and prone to dirty versions, especially the golden red ink is more prone to dirty versions than other color inks. As the weather turns cold and the temperature decreases, the problem of dirty version of golden red ink gradually gets better, and winter is the best time to use it. It is suggested that the proportion of fountain solution should be appropriately increased in order to solve the problem of dirty plates under high temperature printing conditions

⑶ in summer, the printing workshop opens windows and doors, and the air circulation is large, resulting in dry and dirty plates. It is recommended to close the doors and windows and turn on the air conditioner to achieve the effect of cooling. It is best not to turn on the fan, because the fan will dry the printing plate, causing the ink on the plate to be unbalanced and dirty

⑷ the water roller on the plate and the transfer water roller are too dirty, and the ink accumulates too much on the flannelette cover of the water roller, resulting in insufficient water supply and easy to dirty the plate, affecting the printing quality. It is recommended to check the flannelette cover of the water roller every day. If excessive ink accumulation is found, it should be cleaned immediately

⑷ regularly check whether the plate and string of the plate water roller meet the standard requirements. The circumference of the water roller should also be checked frequently. If it is too thick, it is easy to damage the plate, shorten the service life of the zinc oxide plate, and if it is too thin, it will cause dirty plate and paste plate

⑥ in winter, the temperature is low, the air is dry, and the ink fluidity is small. During printing, additives should be added to the ink to increase the fluidity of the ink, but the additives should be appropriate, not too much. Too much will cause too much liquidity, which is easy to cause dirty plates and affect the printing quality. Too little will not work. It is recommended to increase the indoor temperature. If possible, manufacturers can install air humidifiers in the workshop to maintain the indoor dry and humidity balance. (7) after working every day, the machine must be cleaned and wiped clean when cleaning. Whether you use car washing water or gasoline and kerosene, you can't wipe it clean after washing the machine. When you start printing the next day, once gasoline, kerosene and car washing water are mixed with ink or fountain solution to produce a chemical reaction, it is easy to cause dirty plates and directly affect the printing quality. It is suggested to develop good working habits and work carefully and meticulously. At the same time, the cylinder, rubber cylinder and imprint cylinder should be kept clean every day

(8) the tightness of the flannelette cover of the water roller on the plate should be appropriate. Too tight is easy to cause difficulty in installation, too loose is easy to string, run and stretch, and lose its function. There are nylon water roller sleeves and pure cotton chemical fiber blended water roller sleeves on the market. The characteristics of nylon water roller sleeves are: no hair loss of resin based composite materials, and it is better to print color parts, but the disadvantage is that it is easy to stretch, resulting in insufficient water supply. Because zinc oxide plate is mostly used in text printing, it is not suitable for nylon flannelette cover. Pure cotton chemical fiber blended water roller sleeve has good water absorption performance, and will shrink when it meets water, so it is firmly sleeved on the water roller. Nylon water roller sleeve does not have this function. It is recommended to use it according to actual needs

⑼ strictly pay attention to the changes in the use of zinc oxide plate fountain solution powder purchased every time. Every time a new fountain solution powder is purchased, it should be printed and compared with the last purchased fountain solution powder with the same ink, the same plate material and the same dispensing ratio, so as to identify whether the composition of this purchase fountain solution powder has changed, and decide whether to purchase this manufacturer's fountain solution powder. Because there are 4-5 chemical components in the powder of fountain solution, the decline in the price and quality of each powder will directly affect the quality of printing plates in printing, such as inexplicably dirty plates and pasted plates, and there is no way to adjust the machine. It is suggested to pay attention to observation and strictly control the quality procurement of fountain solution and powder

⑽ the font software used in zinc oxide plate making should be thick strokes. For example, Huaguang software is different from some other brand software. For example, the words in Huaguang software font are relatively thick. After printing, it gives people a feeling of thick ink, solid printing and ink foot. Some brand software word libraries have beautiful lines, which are better used in the process of film production, sulfuric acid paper and PS version making, but it is easy to have a sense of false lines and insufficient ink on the zinc oxide version. Although the software itself has the function of bold lines, it can not meet the requirements of printing plants. It is suggested that when purchasing and using software, appropriate selection should be made according to actual needs

based on the above problems, the printing factory will adjust the indentation size of the water roller and ink roller, the pressure requirements of the plate cylinder and rubber cylinder, rubber cylinder and impression cylinder, and then adjust the paper feeding and receiving according to the operation and commissioning procedures of the offset press, so as to achieve a satisfactory printing effect

information source: printing quality and standardization

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