I. Introduction
Litho Graph (Offset) printing is originated from the lithographic ink-repellent printing method invented by Austrian Xue Feileer A. Senefelder in 1797. Lithographic printing is different from other relief printing, intaglio printing, and screen printing to produce printing patterns. Other printing methods only use one kind of flowing ink to produce the print and transfer and fix it on the object. The lithography must use two fluids to produce the printing pattern. The printing pattern (oil) ink can not distinguish the printing pattern on the printing plate (except for the horizontal version), and the printing plate must be coated with water to make the non-printing. The printed part is covered with a layer of water, and the printed part is excluded due to oiliness. When the ink is applied, the printed part is oily and there is no water adhesion, it is easy to make the ink flow on the printed oil On the contrary, in the non-printed part, because there is moisture in advance, the ink layer cannot stick, but only the printed part with grease remains. In printing, the printing ink is taken away by the blanket to reduce it, but the non-printing part of the water is also partly taken away by the blanket. Transfer, rarely notice the fact that the moisture of the non-printed part is transferred, and even the effect of the moisture of the non-printed part remaining on the surface of the printed medium is not noticed, which will cause post-printing ink Difficulties in transfer. If you carefully analyze the water used for lithographic printing, the function is to reject the transfer of ink. The water film layer transferred from the non-printed part of the previous color on the printed medium and remaining on the surface of the printed medium also causes the lower printing ink. When attached, there will be a chance of rejection. Unless there is a well-absorbed paper medium, with sufficient time to absorb, there will be a "dry" printing surface with less moisture for the transfer of the next color ink. Therefore, there is only the Zhangye offset printing machine, which is changed from the one-unit two-color system to the design of a modern offset printing machine with one unit per color. There is no longer a two-color one-unit design.
In theory, everyone says that lithography uses the principle of immiscible mixing of oil and water to achieve the effect of distinguishing prints from non-prints. In fact, this statement has its basis, but not both are 100% unmixed. Often the ink will be transferred to the water supply system, but the ink layer on the printing ink supply system is transferred to the printing plate, blanket and paper surface printing ink, then more or less contains some moisture, unless there is no horizontal printing Probably only 100% ink does not contain water. The reason is that the ink must have a certain percentage of compatible water content to make compromises. The situation is as if there are more or less female estrogen in the male body. If there is too much estrogen, the male has obvious feminine characteristics, otherwise Women are like male hormones, but not too much, otherwise girls will grow beards. The lithographic ink must contain about 5 to 28% of emulsified water. This is a normal phenomenon and a necessary safety zone for buffering. Just like North and South Korea, there is a line separating the two sides along the 38 ° north latitude line. Same as non-military buffers. Police officers are often not enough to catch criminals to solve crimes. Police officers must be present in the underworld's “netizens†to make it easier to control. They may find clues to solve crimes from the inside, otherwise it is difficult to maintain the ecological balance of law and order. . If the lithographic ink is 100% water-repellent, the water-ink balance of lithographic printing is very difficult to balance as if walking on a steel cable. As long as there is a little more water, the printed part will not be removed at all, otherwise A little less water, the non-printed parts all become full version. For lithographic printing, it is easier to control the balance of water and ink. Generally, lithographic printing inks must have a maximum water tolerance of 18 ~ 35%. This is not recommended for printing. When operating, the maximum upper limit is used, because as long as the upper limit of moisture tolerance is passed, not only many emulsified white spots are generated on the print during printing, but even the ink will disintegrate to no viscosity and lose its ability to transfer, but not On the plate ink roller and the printing plate, the printing ink transfer function is completely lost. The ink supply system must be washed and re-inked to print.
In order to make the lithographic printing operation easier, some printing machine manufacturers use the waterless offset method to print in small and small size printing such as plastic cards. This is the printing plate that uses the horizontal ink The rejected silicone rubber layer is used as the surface of the non-printed part, so the ink will not adhere to the surface of the low-dyne material such as the silicone layer when inking to form the print, and will only produce ink on the printed part without silicone When the attached print is transferred for printing, a single fluid printing method is formed. It is only necessary to control the temperature of the printing plate and the ink supply system very accurately, in order to avoid the failure of the ink transfer of the printed part due to the low temperature, or the contamination of the non-printed ink due to the high temperature. Because horizontal printing is a single-fluid printing method, there is no trouble with the ink-and-water dual-fluid printing. It developed in the 1980s, and there are still many supporters. KBA also designed Cortina large water-free printing Machine, it has the advantages of quality, operability, rapid printing start, and less waste, and there is a very new development trend. [next]
2. Uniformity of ink supply and water supply system
If you want to balance the water and ink of the lithographic printing machine, from the ink supply system, water supply system, from the ink tank roller, the water tank roller, to the plate facing (touching) the ink roller closest to the printing plate, you must have a very flat diameter and roller The roundness of the cylinder surface, otherwise the diameter of these rollers is inconsistent, and the surface of the roller is concave and defective, even if the best technician wants to adjust these two systems, it is impossible. As long as the diameter thickness is inconsistent, the surface is depressed, and the deterioration will cause unevenness of the water supply and ink supply, the water supply will be uneven, and the driest place must be kept, and it will not be dirty due to insufficient water. The wettest place must Too much water supply is prone to emulsification problems. If there is less water, it will cause stains due to insufficient water. The unevenness of the water roller is not only a mechanical size, but if each water roller is under the composition of ink or ink mordant (Fan Lishui), it will also make the water supply system partially water-free or water-filled. Reduce, the situation is the same as the broken surface of the water roller. The same is true for the ink roller. The diameter is out of shape, the roundness is not good, and the surface is broken until the surface of the ink roller is stained with hydrophilic colloid. When the water is wet, the ink will be deinked. It is not dirty, but the ink color becomes lighter, and even the whole ink supply area has no ink. Uniformity, no defect on the surface, no adhesion to the water or ink transfer attachments, etc., are all very important conditions in the balance of water and ink, in order to have a smoother printing.
The proper hardness and proper roller pressure adjustment of the water roller and ink roller are also important factors for the transfer of water-based ink, because many people apply the ink roller, water roller, and even the printing cylinder to the full version of the ink to see the touch The width and narrowness can be used as a reference to determine the pressure of the printing machine to adjust the roller pressure. This is only relative accuracy, but not absolute accuracy. As for what is relative accuracy? For example, the touch width of 5mm is too heavy! If it is adjusted to 4mm or 3mm, it must be light, while 6mm is the heavier touch. However, if the diameter of the roller or the printing cylinder is different, the same contact amplitude does not mean that the pressure is the same. If the diameter is doubled, the contact amplitude must be doubled to be the same. Calculated by reducing its exposure, the pressure can be appropriately generated without being too heavy. In addition, all the rubber ink rollers and printing rollers of the lithographic printing machine are arranged in a hard and soft phase, and the soft rubber roller or the rubber cylinder equipped with a rubber cloth is used as a shrinking elastic body when pressed. These rubber elasticity and hardness (Shore Hardness) Shore hardness values ​​also affect the pressure. With the same large contact depth or amplitude, the hard rubber roller will generate greater pressure, and the soft rubber roller or blanket and The liner produces a smaller pressure response, so the intrusion pressure of the hard liner can only have a pressure of 0.05 ~ 0.07mm, the medium-hard type can have a pressure of 0.12 ~ 0.15mm, and the soft liner can reach an intrusion pressure of 0.2 ~ 0.3mm. Otherwise, the ink transferability of the full version will be poor. As for insufficient pressure, due to poor water transfer and ink transfer, an extremely thick water layer and ink layer are needed to transfer between abnormal gaps. Naturally, there is no real need for ink and water supply layers. Water or ink supply. If abnormal production is carried out under the emulsification of a large number of thick-film inks, not only will the ink transfer properties be poor, but also the prints on the printed matter will swell, delay drying, and backprinting will occur, and the ink color will be dull and the dots expanded. It is common for many ink rollers and water rollers to be used for a long time. The rubber of the roller is thinned due to the release of the material, resulting in insufficient pressure of the ink roller and water roller, and must be shut down for inspection. On the waste plate that is no longer preserved after printing, put down four contact ink rollers or a water roller against the printing plate. At least you can check the pressure of the final pass to the plate. Can it be stored normally? After the machine is stopped, press the normal rotation or reverse rotation according to the inch, and see if the traces of the lateral touch amplitude on the surface of the roller are consistent, and the touch amplitude is moderate? However, the method of the rollers inside does not work. Therefore, the method of touching the screen to see the pressure of the printing machine has its convenience and reference, but the diameter and hardness of the test object are also another reference index. If the pressure of the ink roller is too large and the width of the ink is too wide, it will not only change the amount of ink transfer, but also make it easier to soften the heat of the ink, which may cause emulsification and reduce the amount of ink supply. Injury problems.
The ink roller must have oleophilic rubber in order to keep the printing ink attached, and it is not easy to be deinked due to the adhesion of the colloid of moist water. On the other hand, the water roller needs softer hydrophilic rubber. If the ink roller oleophilic rubber is used, the water supply will be greatly reduced, and it is easy to cause ink staining to affect the water supply. More importantly, the water roller does not If the ink is evenly stained, it is necessary to increase the amount of water so that the lowest water supply block has enough water, then the area without water will be too much water! Severe emulsification of the area occurs, this kind of uneven water supply, the degree of unsmoothness is not less than the deformation of the diameter of the water roller.
Ink rollers are generally divided into two or three different rubber hardness levels. The rubber near the upper part of the ink tank roller and the riding roller is harder, about 35 ° Shore. The ink roller on the layout should be softer to reduce impact streaks. And the plate head is smooth with 28 ~ 30 ° Shore, and the other is between 30 ~ 35 ° Shore. The water roller uses very soft hydrophilic rubber with a hardness of about 18 ~ 22 ° Shore. If the water roller is too hard, the water supply will decrease due to the increased pressure. At present, many manufacturers have changed the water tank roller from chrome plating to a water tank roller on the ceramic surface. On the one hand, it can avoid the formation of chromium oxide and hinder the hydrophilicity of the chrome roller. On the other hand, the ceramic water roller maintains good and long-term hydrophilicity. According to this, IPA isopropyl alcohol is reduced or not used, and a more environmentally friendly purpose is achieved. [next]
3. Temperature control and additives of water supply system
Water is a liquid state. After reaching the critical point of molecular disturbance due to the absorption of heat, when the vapor pressure in the air is small, it quickly escapes into the air. Conversely, when the water absorbs the same heat but the vapor in the air reaches 100% humidity It is difficult for water to be converted into steam and escape into the air, and it needs more heat to evaporate. From this example, we can understand that in the water-ink balance, if the water supply is the same, the closer the humidity in the air is to saturation at low temperature, the less water will evaporate and the more water will be retained on the layout. Conversely, high temperature, low humidity in the air, low vapor pressure, and the faster the moisture evaporates, the lack of moisture will occur. These will cause a lot of changes in the balance of water and ink during the operation of the lithographic printing machine, which causes the moisture on the printing plate. A large amount of evaporation is insufficient, resulting in dry spots where the printing ink accumulates in the non-printed part. In addition, due to moisture under low temperature and high humidity, excessive emulsification of the water supply occurs. If printed on white paper, it will be a large amount of paper that absorbs water. , Will also increase the consumption of humid water; printing copperplate paper with less water absorption, even plastics, synthetic paper, and metal foils that do not absorb water, then the moisture consumption is equal to zero, so that the moisture becomes too much, so Water consumption is divided into three aspects: one is the size of the page, the temperature and humidity, the printing speed, the size of the layout is large, and the printing speed is fast. It increases in proportion to the water consumption, and the speed is fast, the temperature may increase and the evaporation of thermal disturbance increases, the other The reason is that the increase in the printing speed and the increase in the printing volume will increase the water taken away by the paper and the water taken away by the emulsification of the ink. (The consumption ratio of the two is because the emulsified water is used when there are many prints. Increased, due to the increased water absorption of non-printed white paper and increased water consumption). The temperature of these ink rollers rises due to the viscous drawing of the ink, or heat is generated because the ink roller swings the rubber roller, which quickly generates a temperature increase and changes the water-ink balance. Generally, lithographic printing absorbs a large amount of heat due to a large amount of water evaporation, but it is generally appropriate to use 25 ° C. Therefore, all lithographic machines currently use a humidified water cooling system to reduce water evaporation and maintain ink in the ink supply system. The layer reduces emulsification due to good astringency. But as the speed of the printing press becomes faster and faster, from 6,000 to 7,000 sheets per hour to 15,000, 16,000, 18,000 sheets per hour, it is impossible to keep the temperature of the ink supply system stable simply by the low temperature of the humid water, so Most Zhangye offset printing machines today use hollow steel rollers to circulate cooling water to reduce the temperature of the ink supply system. As long as the temperature rises above 150 ° C, the ink hardness will be softened, the resistance to splitting will be reduced, and the ink viscosity will be reduced. Reducing the amount of transferred ink becomes less, and it is easy to emulsify, which is the main reason that the printing ink color is lightened on the paper surface under high speed and long rotation. Due to the softening of the ink, the mid-tone dots increase and the version tone cannot be controlled. Unlike the normal performance of the initial printing chiller, the mid-tones do not change due to the increase of the dots and the darkening and lightening. On the contrary, the ink density of the full version and the dark tone decreases. The quality of the lightening is reduced. Therefore, not only the horizontal printing machine, but also the general horizontal printing machine. In addition to the water roller system in the water tank to reduce the water temperature control, the ink roller system is also equipped with a cooling water cooling system, through the ink roller or ink tank roller The center absorbs heat to keep the temperature of the ink roller from rising.
Some acidic substances and colloids must be added to the tank liquid. In the past, ammonium nitrate, ammonium phosphate or ammonium dichromate was used. Among them, in addition to maintaining the acidity of the water quality, ammonium dichromate can prevent the ink from becoming alkaline due to the tank liquid. Grease is "saponified", and the ink decomposes and dissolves into water, causing fat and pigment pollution. The plate surface adsorbs dichromic acid molecules to form a surface that is not easily oxidized and dirty. Before the PS version was developed, it was a very serious problem. Useful anti-oxidation, anti-paper powder rubbing the layout, a very effective way to keep non-printing clean. At the beginning of the PS version, the aluminum plate surface was not anodized. After printing textbooks for thousands of revolutions, the aluminum material will be absorbed by the bath liquid. Too much alkaline chemical substances on the paper surface will cause corrosion and cause the print to fall off. Later, after switching to anodizing treatment, not only the layout increased to 9 degrees high hardness and wear resistance, but also the ability to resist alkaline chemical corrosion has also been greatly enhanced. Therefore, most of the water tank liquid is mainly maintained at an acidic environment of 4.5 ~ 5.5PH, but the printing press rotary machine is produced in a weak alkaline environment above PH7 because the printing ink is not very saponified. In order to resist the contamination of the alkaline substances dissolved from the paper surface, and the acidity of the plate surface can maintain the convergence of the ink, the print will not increase, adding acidic substances to fight against is an important component of the current hydrophilic liquid. The pH value buffer is added to the tank liquid to maintain the value from the normal pH 4.5 to 5.5, so the true pH data is often not measured, but only to maintain a certain degree of action, so there is a conductivity detection method, which is based on resistivity Detect the true content of the acid value of the moist water and no longer be affected by the buffer. In the past, when the quality of the printed paper was poor, there was a thin layer of gum arabic on the printing plate surface to improve the printing surface and have better hydrophilicity. However, when there are many paper wool and paper powder, the printing surface will be smoothed and lose the best. Hydrophilic water content, so it is necessary to rely on the colloid contained in the tank liquid to supplement the consumption of the arabic gum layer. Now almost no glue is added, because the PS version and CTP version are all treated with hardened oxygen polarization to form alumina hard The film is very abrasion-resistant, so the modern water tank is composed of hydrophilic treatment liquid, interface active agent, PH control and buffer, and then IPA isopropyl alcohol.
Today, a humidified water system without IPA is added to avoid evaporating VOCs and affecting the environment, but how to deal with the lack of IPA? First, we must filter and remove calcium, magnesium, iron, manganese and other minerals in the water, so that the water quality is softened, there is a greater wetting capacity, and the oil quality and pollutants in the water should also be removed, and the good wetting power close to "pure water" is always maintained. Some even use UV lamps for photocatalytic sterilization to reduce the occurrence of suspended matter and mold in the water, which affects and blocks the smoothness of the water pipes. Now, alcohol-free humidified water systems are also popular and are the development direction under the demand of environmental protection. [next]
4. The printing ink supply layer is a fixed-height drum with balanced water and ink
Water and ink balance is the interrelation of water layer and ink layer to maintain the least ink layer to print the appropriate color, and the thinnest water film, plus a little safety factor to keep the printing plate clean, is the best for water and ink balance in principle. But the seemingly easy operating conditions, in actual operation, the new printing machine is generally easier to achieve ink and ink balance, the main reason is that the ink roller, water roller each flat, good roundness, and the rubber elasticity is good Claim. Therefore, the thickness of the ink layer on the left and right sides is easy to be uniform and the ink and water layers are accurately transferred. The ability to reflect ink and reduce ink and water and water is as fast and accurate as expected. In an old printing press, first the rubber hardens, bulges, and shrinks, and the pressure changes unevenly. Even two of the four plate rollers are inked on the printing plate, and the left and right pressures are not uniform, resulting in ghosts, The streaks and the ink layer are also rough because there is no good ink leveling, which is easy to stain on the back. If the color is insufficient, the ink layer should be thickened to achieve the ink color, and the water and ink will be out of balance. The same situation occurs when the water supply system with only one plate water roller is more serious, so many large printing press manufacturers today return to the previous emulsified ink and water configuration. The first ink roller is a method of mixing water and ink. Produces greater tolerance and elasticity in the balance of water and ink. Therefore, every three or four months (now the rubber is more stable than before), the pressure of the water roller and ink roller must be checked and adjusted. The surface of the water roller must be smooth grease combined with alkaline detergent. Similarly, the surface of the ink roller often becomes smooth without pores due to the mordant cured resin layer in the ink, and loses the traction of the rubber surface of the surface and the ability of drawing ink to transfer ink to drawing, and its ink uniformity and ink supply capacity are reduced. Even more advanced, the No. 1 and No. 2 plate ink rollers close to the water roller, and the hard swing roller driven above, if the surface is coated with colloid, it is easy to produce a segmental hydrophilic deinking phenomenon when there is much moisture , Making the ink supply extremely uneven. This situation often occurs in the water roller. If the ink layer adheres to the section, the total water supply must be increased to obtain the amount of water in the ink-blocked section, that is, the water in the minimum and minimum water supply section is still not available. Insufficient, it will avoid the occurrence of plate blotches, but when there is too much moisture, some parts will exceed 50% and 100% of the standard! The ink tank roller has an ink key to control the amount of ink change in the section. On the contrary, the water roller does not currently have a section control key, and only blows the ink roller section to evaporate the emulsified water of the ink roller in the section as excess water. Balance function. Therefore, the pressure adjustment of the ink roller and water roller, the rubber surface retains its own lipophilicity, hydrophilicity, and elasticity and roundness, which will affect the section and even the overall water-ink balance. Some printing machines, especially above the plate ink roller, have gears to drive the oscillating ink roller, but because the ink roller of the cleaning ink roller presses the ink on the surface, after a long time, the diameter of the oscillating ink roller becomes smaller due to wear, making the ink roller The surface speed becomes slower, which does not conform to the normal speed of the plate roller surface, which causes the "? X car" phenomenon during operation. This will also cause dirty streaks and ink stains. Some water must be turned on to reduce its slow sliding. The stains, which also affect the basic water-ink balance, should be cleaned and processed to remove the hard ink rollers.
It is easy to talk about water and ink balance when the water roller and ink roller of the printing press are in normal conditions, otherwise the water and ink balance is in "abnormal balance" under abnormal conditions. The operator should always pay attention to the water content, but not too much, but less Insufficient dirt and dry ink spots cannot occur in the moisture section. Today's modernization CIP 3 / CIP 4, to send the information of the pre-press layout to the ink key section, the original juice, the original flavor to the printing machine, there must be a set of different ink properties, printing machine room temperature and humidity, paper, printing pressure According to the requirements of customers, the ink key opening of each color and each ink key area is converted. This conversion curve changes every printing company, every different printing machine, and even every printing machine has its own experience. The conversion curve of the value is placed on the computer software plug-in of the ink control system of the printing press for the most suitable conversion. Then, after the printing is started, the ink supply of each ink key zone should have a very consistent and stable continuous ink supply, without excessive and Insufficient, compared with the previous master to use the percentage of the cumulative value of the printed patterns on the printing plate to adjust the ink key, it has its absolute advantages and advantages. But the premise is that the zeroing and leveling of the ink tank key must be done well, otherwise Gaoming Technology is built on the inconsistent starting point, and it is easy to change in a small amount of ink supply area, especially 5 to 10% of the ink keys Errors will cause many data to be confused. Originally, the opening degree of the ink fountain key is inversely proportional to the amount of ink transferred from the rotation angle of the ink fountain roller, so the average opening of the ink key is large, and the output amount of the ink fountain roller should be correspondingly small; on the contrary, the average opening of the ink key is small; the ink roller The transfer ink should be opened relatively large, so the average opening of the ink key of the printing machine that is not accurate to zero is larger to reduce the interference of the error value. In the previous edition, the ink key responded to the distribution of the printing pattern, so that the ink layers in the upper section of the ink supply system showed different ink layer thicknesses. It must also be adjusted before the next section of printing. Otherwise, it will affect the color change during proofreading. Therefore, some printing machines have an intelligent leveling function. When this version prints to 10 to 20 sheets of mantissa, the ink tank key will be averaged, such as the average ink supply of 10% and 15%. The ink key area with large ink consumption takes away more ink layers, leaving a relatively even ink layer for the next print. If the ink volume is even, the ink consumption is less than 15%. It is not necessary for this pattern to smooth out the unevenness of the ink supply layer above.
Unlike the gravure printing machine, which has extremely fixed ink supply thickness and flexo printing machines and flat printing machines equipped with Anilox Roller micro-cavity roller ink supply, Anilox Roller's ink cavity distribution and depth determine the thickness of the ink supply layer on the layout In addition, in letterpress printing and lithographic printing, the ink layer distributed from the gap between the ink tank and the ink tank key is transferred five to seven times before the cloth ink is generated at the print on the surface of the printing plate, so the ink layer The flow of ink from the key gap to the plate surface and the thickness of the ink layer on the plate itself can not only show the printing density, but also form a water supply. Whether it is a key factor to form a clean and suitable color printing ink balance, and this ratio relationship from the ink layer to the water supply layer cannot be operated invariably. It also depends on the ink layer thickness change and temperature change of the ink supply system. It is improved due to the dryness of the ink skin, the mixing of paper powder and paper wool. On the other hand, the situation of water supply includes changes in temperature, evaporation of water, contamination of the water roller, PH value, water absorption of printing paper, and humidity in the air, which affects how much water evaporation changes. Therefore, the main reason is how much ink is supplied, and there are still many factors that affect the changes of the balance between water and ink. [next]
Fifth, the moist water went there in the end of printing
Most printing workers and printing company managers, although they are very careful in managing the ink they bought for a lot of money, where did they go, whether there is good color reproduction and printability performance, but they rarely pay attention to it Where is the humid water priced in tons using tap water? Where to get moisture: (1) Paper absorption, which is different due to different materials. Smooth coated paper absorbs little moisture, followed by snow paper, lightly coated paper is more, non-coated paper is quite much, and porous Non-glued cotton paper and newsprint absorb more, while synthetic paper, plastic, paper with gummed film, and foil paper hardly absorb moisture. For the same type of paper, the high humidity itself absorbs relatively little water, and the low humidity relatively absorbs more water, and the total amount of moisture absorbed by the paper will increase in direct proportion to the printing speed (print volume). (2) Evaporation is a very important part of water consumption. The more the printing plate surface is evaporated, the more closed the flat press is, which reduces the ratio a lot. Instead, there is a non-printed part with moisture on the surface of the blanket and the pressure roller It is a large part of the evaporation of water, especially the double-diameter and triple-diameter pressure rollers. When there is no paper, the size of the roller is large, which causes a greater percentage of water evaporation. (3) The evaporation of the emulsified water in the ink layer on the ink roller is also an indirect water evaporation. In addition to the evaporation of the printing area, the three types of evaporation will not increase due to the increase in printing speed. The evaporation itself is closely related to the air pressure, wind disturbance, temperature, and humidity in the printing machine room. This also causes a major factor in the change of the ink and ink balance. Usually the temperature is high, the moisture of the natural moisturizing water in the water roller, ink roller emulsified water, plate surface and other parts not printed on the cylinder surface will increase the evaporation. High humidity will reduce the evaporation of water from all parts. Today, due to the cooling of the ink roller, the freezing temperature control of the water supply system, and the temperature control of the printing machine room, the temperature has little change factor throughout the year. On the other hand is the humidity factor, which is often a variable that is not easily noticed by the printing machine room and less noticed by people, but it often affects the water balance of the printing machine. Many people mistakenly think that the addition of a cooling air conditioner is an air conditioner. In fact, only A single tool for lowering the temperature of the printing machine room sometimes has the effect of removing excess water from the air. The real air conditioner should have four functions: cooling, heating in winter, dehumidification and humidification. Therefore, the functions of the dehumidifier and humidifier are very important in the air conditioner. It is not only the cooling of the air conditioner, but also the air conditioner is expected to shoulder the role To remove excess water, the winter room temperature is only 13 ° C and the relative humidity is 90%. This is also a very difficult printing condition, and the paper will stretch and deform. Therefore, it is not suitable to use the air conditioner to dehumidify. It should be equipped with a cold exhaust dehumidifier. Not only dehumidification but also the function of raising the room temperature is a good method. In summer, the air conditioner has the functions of cooling and dehumidifying, killing two birds with one stone, keeping the humidity of the printing machine room stable, and increasing the balance of printing ink and printing quality and the stability of printing quality. If the printing machine room is cooled in the summer thunderstorm or rainy season with a 50 to 60 ton air conditioner, you can see that the water in the air is like a third of the flow of the tap, because the water in the outside atmosphere, and two or three In a four-color flat printing machine, the evaporated water is in the spectrum of five or six hundred liters per day, so it is nothing special for an air conditioner to remove 800 to 1,000 liters of water a day. It can be seen that keeping the humidity of the printing machine room at 50 to 60 % Is more appropriate in Taiwan, but 45 ~ 55% is more appropriate in winter. If the printer is too dry, the water consumption will increase a lot.
Some people think that the faster the speed of the printing press, the higher the water supply. Some people think that the scale of the water supply on the printing press should be reduced. This sounds very contradictory, but each has its own argument and basis, and there is not necessarily a conflict. Basically, the faster the speed of the printing press, the greater the number of prints. Regardless of the ink emulsification, paper absorption, and temperature increase of the printing press, the thermal disturbance increases, and it is a fact that the amount of water used for evaporation increases. But on the other hand, the evaporation of water on the surface of the outer cylinder of the printing plate and printing paper has not increased, so the speed is increased, and the water demand will increase, but there is no proportional increase. If the water receiving roller takes water once for each printing, or Take two waters at a time, then the faster the printing speed, the more water will be taken, and the specific consumption will be OK. However, when the unequal consumption is evaporated, the extra water will cause extra problems. On the contrary, if the continuous water supply always sends the water to the humidification system, then the ink emulsified water, paper absorption water and heat disturbance increase more and need water, so we need to increase the water supply by using the fast water tank roller speed, otherwise the water supply It will be insufficient, and there are different opinions on how to write this program. [next]
6. Some changes in lithographic printing plates
Ink and moist water are the main roles in the lithography process, they play a dynamic blending work and role. But do n’t forget that the more important thing is the “printing plateâ€. This piece can both distribute and absorb water, and at the same time, it can absorb ink at the “printed part†of the place to be printed. This is an extremely important platform for water and ink to balance the performance. .
More than two hundred years ago, this platform was built on the limestone of Austria and the southern Alps of Germany. This milky white porous limestone board has good water absorption. But after accidentally dropping the candle, use a cloth with grease and water. When wiping, it is found that not only the wax has not been wiped off, but the water and oil are separated by the water and oil. It also promotes the principle of semi-physical and semi-chemical printing methods in which lithographic printing can separate non-printed and printed parts with a single plane. Although there has been a long and glorious era of hand-printed color printing, hand-printed color lithographs in Japan, lithographic posters in Shanghai, and lithographic posters in Europe and the United States, lithographic prints are still popular today, but heavy lithography can only be manual and mechanical Platform printing can not enter the list of high-speed printing. It was only in 1903 that Mr. ZW Rubel of the United States invented the current indirect printing method Offset Zhangye lithographic printing machine, which used zinc metal lithography. The zinc lithographic material itself is almost between hydrophilic and lipophilic, so the non-printed part of the printing plate is not easy to get dirty with water, and the lipophilic part of the printed part is also medium, which is better than copper Much worse. In addition, the zinc plate material is easy to oxidize. Once oxidized, it becomes a non-hydrophilic and ink-free zinc oxide. This kind of wall-riding substance that is very incompatible with printing is placed on the non-printed part and becomes a gray spot. In the printed part, the white spots are not full, so the work on the zinc plate needs to use more water to keep the non-printed part of the plate clean. On the other hand, it is necessary to prevent the plate material from making before the plate and The zinc material of the printing surface of the printing plate after plate making, printing, and preservation is oxidized. Zinc printing plate grains are coarser than aluminum material, easy to wear, and are also unfavorable for long printing. The aluminum plate is now used, which has a very good effect in terms of hydrophilicity. In addition, the grain (grain) of the plate is very fine, but it is deeper and has a larger water content. With the anodizing treatment, the oxidation The hardness of aluminum is as high as 9, which is higher than that of most gemstones, second only to diamonds, and besides the strong wear resistance of the oxygen-polarized aluminum oxide layer, it has more porous microstructures, forming a triple-type non-imprint with large water content. With less moisturizing water, reasonable water-ink balance printing can be done on the grain part. Changing from zinc to aluminum for printing plate is very helpful for lithography, easier to operate, less dirty, and aluminum is lighter than zinc a lot of.
In the early development of the PS version in the 1970s, 3M also introduced unpolished aluminum plates, which are difficult to control the moisture of the plate surface, so they were unsuccessful. Another multi-layer plate is used for lithographic printing and is also a very successful printing plate, which can withstand millions of sheets for packaging and metal printing. The outermost layer of the multi-layer version is chromium metal with excellent hydrophilicity. As the non-printed part, the bottom is red copper (red copper) which has good lipophilicity. There are three layers in the production, some are made of steel, and the surface is first plated with copper and then chrome. The plate is printed with a positive film in the form of a flat gravure. The red copper layer is exposed. When printing in the future, the chromium plating layer can absorb moisture, and the printed copper layer can absorb oil, forming a fully metal stable and high-efficiency printing plate, and the wear resistance is three to fifty times that of the general printing plate. Materials such as zinc and aluminum. The double-layer full version is made of chrome-plated copper, but the plate is not resistant to printing mechanical impact, so the steel-based three-layer version is more practical, but no one has introduced it in Taiwan. Because the cost of the plate is very high, the printing volume is not large enough Enough to use this type of printing plate.
Nowadays, with the PS plate and CTP plate as the mainstream plates for lithographic printing, there are many difficulties in the early PS plate. For example, the printing pattern is not resistant to the acid and alkalinity of the paper. Too much acid and alkali will fall off. The change is due to the fact that the paper coating layer and pulp filler chemicals dissolved from the printing paper surface will be wet from the wet blanket surface, and will be traced back to the printing plate, water roller, and water tank, forming a chemical hoard, As a result, the printing pattern is corroded and is not durable. As soon as thousands of sheets will be out of print, it can not be used. Therefore, it is effective to replace the printing paper by baking the plate to glaze the printing pattern, or to replace the sink liquid and clean the wetting system. I remember that when I printed a classmate's record in the factory, I printed three or four sets per hour (manually installed), and printed three to five hundred at a time. I used a plate water roller to wet and dissolve the glue on the plate for half a day. , The printing pattern will not be inked, mainly because there is too much water glue and acid is too strong, so that the ink of the ink supply system loses a lot of oiliness due to too much glue mixed, so the manual plate washing is used to remove the glue and clean the ink roller , Water roller, restart printing to work smoothly. If the water tank is not used for a long time, it will tend to ferment and grow mold, which is not conducive to the effect of moistening water.
The non-printed part of the plate must be glued before printing, so that a thin layer of arabic acid glue is attached to it to exert the long-term water absorption of colloidal molecules, so it is said that flat printing is not only the physical incompatibility of water and ink In addition to the principle, there are many meta-chemical principles.
How to maintain the good water absorption of the non-printed part of the plate, in addition to the above-mentioned plate alloy composition, grinding, acid etching and anodizing the surface hydrophilicity of the aluminum plate, the plate is coated with light and heat After the development of the coating layer that forms the print, if it is not completely clean, and there are coating layers and coating films remaining, then the water resistance of the printing plate will definitely be affected. A large amount of water can be used to keep the printing plate clean. Therefore, in addition to maintenance and repair of the plate developing machine, it is very important to maintain the temperature and strength of the developer. It is very important to replace or replenish the developer. Otherwise, if the temperature is insufficient and the drug is too weak, it will become dirty due to insufficient development. On the contrary, if the medicinal properties are too high and the temperature is high, the printed part will weaken and the printed part will become thinner after developing for a long time. Compared to insufficient development, the negative and positive plates will get dirty regardless of the negative type, then the negative version of the PS and CTP versions will not be exposed, will not get dirty, and will only make the combination of prints insufficient and easy to fall off Version. The positive plate type is a light decomposition type. When the PS plate UV light is insufficient or the light source is weak, the CTP plate speed is too fast or the light source is degraded, it will affect the underexposure. Once the underexposure will cause a residual coating layer after development Dirty conditions make printing difficult. As for the post-exposure positive plate after the completion of the printing plate, once the post-exposure print pattern becomes weak, it is the result of multi-sensitivity and decomposition of the coating layer. On the contrary, the post-exposure of the negative plate has a combined effect of strengthening the print pattern. The coating layer will become more dirty, which is not good for printing and water distribution in the future, which is not beneficial to the printing plate. Therefore, the condition of the plate material and the absorption of ink on the printed and non-printed patterns formed by the printing plate, The water-absorption boundary must be handled very carefully so that the work can be smoother and more enjoyable, and the good quality of lithography can be maintained. [next]
7. Conclusion
An excellent lithographic printing machine operator, to today's technologically advanced era, although it has many advanced precision machinery, motors and electronic equipment, under the control of many hardware and software, even the very difficult ink roller swing amplitude and swing phase are all You can do fine-tune change control on the console. Others such as turning mechanism, the phase change of the front and rear printing press cylinders, and the bite claws are opened and closed from the normal paper receiving, and the torsion turning to catch the tail of the paper back and forth, these are extremely accurate and The complex control work can be done by modern printing machines, not to mention the size of CIP 3 / CIP 4, the reception and presetting of ink key information. Therefore, Manroland changed the flat press to only press a Start key, and all the projects were executed under the programmed system. However, the advantages of our lithographic printing machine, using thin and cheap aluminum materials, and high-precision 2400dpi, 3000dpi high-precision CTP plate-making machine, can produce a printing plate from 500mm to 2860mm, all with very good overprint accuracy, printing plate from Enter to install fully automated.
The engineering of the printing machine takes four to fifty years, and find ways to measure the thickness of the wet film on the printing plate. According to the visual observation passed by the previous teacher, the gloss of the side of the printing plate is viewed at a side of about 10 ° to estimate the amount of moisture in the non-printed part of the printing plate. With the banner surface of the printed sheet, it is easier to see Blocks that lose moisture are added for monitoring. Keep the prints clean in this area to reduce the total water supply. If the dryness of the test immediately appears dry spots, it means that the water supply has reached the critical point of the lower limit of this danger zone. It is necessary to increase the water supply a little higher to make it difficult. Defective output. And the teacher often depends on the weather changes. At noon and afternoon, the temperature is increased and the water is reduced on rainy days. When a wind blows from the window, the printing plate will dry off near the window. Quickly sprinkle water to make up the water. Observe that, with the slow and poor production rhythm at that time, it is feasible to control the monochromatic machine and the two-color machine, because these have a deep understanding of a certain environment and the ink and ink balance characteristics of each block of the machine, and are formed according to the countermeasures. A "work" that can be produced. Today, the Zhangye offset printing machine is not only four-color, six-color, but also eight-color and ten-color. It is not only impossible to manually look at and visually inspect the water film distribution of each printing plate on the cylinder, and the printing machine is now in a small amount. In a variety of production environments, it is not allowed to observe the water supply of various printing plates manually, but based on the speculation of the workers. This is a big door to the high-cost and high-productivity lithographic machines worth tens of millions and hundreds of millions. It is also very ironic that the normal printed sheets were printed in the last minute, and after 250 or 550 sheets in the next minute, a pile of waste printed matter that was too dry and too wet was produced! This very drastic change does not exist in the production of high-speed gravure and flexographic printing presses. Therefore, using optical methods, infrared measuring instruments, microwave reflection and other technologies, I want to measure the R & D technology of the water film thickness of each block on the lithographic printing plate. Although there are so many high-tech measurement procedures, there is still no success today. , Gong enters practical control. Even the horizontal printing method using Anilox Roller ink supply roller has a more uniform ink layer printing method, but it has not succeeded in simply controlling the water-ink balance, and special inks must be used to print normally. It can be seen that the difficult scene of ink and ink balance is still conjectured on the basis of experience on high-tech lithographic printing machines. This is hundreds of thousands of lithographic press operators. Every day, this speculation is enough and insufficient to operate production. High-quality products and high-yield prints are facts and extremely frustrating. Therefore, we should adjust the water supply, ink supply and elasticity, precision, pressure, and surface conditions of the printing press, and then seek to improve the ink and water conditions of the printing plate, and control the temperature and humidity of the printing machine room, as well as the ink and consumables. Quality management, plus CIP 4 data distribution, I believe that under desperate conditions, we may still have to continue printing in lithographic mode for another 50 years or 100 years. This history of the struggle of ink and ink balance will continue to be written. Go on.
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