Analysis of Continuous Change Supply of Printing and Moist Water

1. Lithography, ink balance principle Lithography uses moist water to keep the non-printed part clean. This is the principle and method that has been used for more than two hundred years. How much water supply directly affects the quality of lithographic printing, too little water can not keep the non-printed part clean, small and fine anti-white words will get rid of or dragging the edges of the word, and even the whole film of ink spots, and vice versa. For a long time, the ink became lighter, the full version had white spots, or the entire white water mark was in the printed area, and even the last line and text disappeared first, and the printed ink had a feeling of being completely washed away.

UV ink drying is more affected by water. Over-emulsified ink layer will be cured by irradiation and other problems. Even if it is generally non-forced drying ink, it is not easy to dry under too much water and excessive emulsification. In fact, the ink on the ink supply system of the typographic printer will also cause too much water in the ink due to too much water for a long time, which will cause the viscosity of the ink to drop, and the ink on the top will not move down. The ink only transfers a small part to the lower layout ink roller to the printing plate, resulting in serious ink color reduction, even hard steel roller, copper roller will have deinking phenomenon, and the printing quality can not be used.

2. Water Consumption Analysis Let's first discuss where is the moisture on the typographic machine? The first is the consumption of ink emulsification, the second is the consumption of evaporation, and the third is the consumption of paper.

The first ink emulsification can only be between 15 and 20%. If 8000 four-color prints are finished per hour, three kilograms of ink and five liters of moist water are used, meaning emulsified water, only 0.45- 0.75 liters may be consumed with the ink consumed on the plate, so this amount is 9-15% of the total moisture consumption, the third paper absorbs, if 8000 sheets are calculated with a basis weight of 100g/M2, and 342 kilograms 0.4% more paper. For the weight of water, its excess water of 1.37 kg of water is consumed from the wet system. The second evaporation consumes about 2.88 to 3.18 liters of bulk drugs, accounting for more than 50% of the wet water.

In addition to layout evaporation, the blanket surface, pressure roller surface, and ink supply system will evaporate more or less. Although the printing plate area does not change due to the speed of printing, the ink supply system of the printing press is accelerated due to the speed increase. As the temperature rises, the evaporation rate increases. However, if the ink supply system is equipped with a constant-temperature cooling water device, this will not happen.

The faster the printing speed, the greater the wind disturbances on the drum surfaces and the more evaporation, and the biggest problem in the management of moist water is that there are too many variables involved in evaporation water changes (including the above-mentioned high-speed ink roller heating The combination of wind, wind disturbances, atmospheric temperature, humidity changes, and the total combination of wind direction in the printing room, etc.) creates a logical pattern of how much water supply is extremely complex and variable, which is the focus of this article.

3. Environment and typographic machine conditions Many typographer operators cannot understand the changes in these internal mechanical structures and control and external conditions. Therefore, under certain conditions, they can still produce, but as long as the internal and external factors are generated. , they panic and can not be strained, resulting in low quality, even unsuitable use of poor printing conditions.

A. The best conditions The best conditions are the constant temperature and humidity of the factory, and the printer itself also has a constant temperature ink roller and wet water device. The printer operators are faced with changes in the absorption of water of different sizes and different papers. , embossing ink size embossing, and the speed of high and low printing amount of water consumption change. Of course, changes in size and speed of printing can be used for predictable arithmetical problems. As for paper, paper, white paper, molded paper, and doline paper are more absorbent, micro-coated and light-coated, followed by snow. Paper is next. Glossy coated paper is very hygroscopic. Mirrored paper, full paper, and plastic sheets are barely absorbed. Therefore, the water consumption may be a quarter-to-quarter gap, and the problem is not obvious.

B. The printing room has a constant temperature and humidity condition. The printing room has a constant temperature and constant humidity. However, the printing machine only has a constant temperature for the water and the ink does not cool the constant temperature device. In this case, the temperature of the printing press to the ink system at high speed operation will be It rises, but under the cooling of the moist water and absorption of evaporation heat, the long-term operating temperature will increase by 5 to 10°C, which will affect the evaporation of water. At the same time, the ink will soften when the temperature rises, and it will be more easily stained. As for printing plates, the amount of water is also increased. Therefore, it is necessary to increase the water compensation setting at high-speed printing. Others work under the condition of A.

C. The printing room has air-conditioning and humidity-free conditions. The printing room has air-conditioning, but there is no constant-humidity addition and subtraction humidity device, and the printing machine has only a cooling and constant temperature device for moist water. Basically, the adjustment condition of A+B is very similar, only In the dry season in autumn and winter, wetting water should increase, while wet weather and more humid weather in northwestern China during the summer, originally evaporating water accounted for 50% may be only 15 to 20%, so it must be greatly adjusted in response to the humidity in the air. The factors cause moisture vaporization of the moisture and cause the printer plate, blanket, pressure roller and ink roller surface water to change.

D. There is no air conditioning in the printing room. The printing room is open without air conditioning. The printing machine only humidifies the water and has a cooling thermostat. In this environment, it can be said that it is not conducive to long-term work. The temperature rise during printing is about 5 to 10°C in half an hour. In between one hour and two hours, if it is possible to reach 15°C outside in the summer, the cooling effect of moist water will not be significant, and if it is in autumn and winter, the increase can be reduced. Imagine 27 to 28 degrees Celsius in the summer morning. Once it rises to 42 to 43 degrees Celsius, plus heat dissipation from the motor, pump, and cooling water, it will cause serious problems on the motor side. The plate will have different heat on the left and right sides. Different evaporation ratios occur, and the motor side is more prone to dry spots.

However, openness is not only caused by a single temperature increase, but also by factors such as near-window drying, uneven drying, and disturbed sunlight. It is not easy to do quality uniformity because the operator must be fine because of temperature rise, wind disturbance and Changes in the external temperature caused by changes in order to do a good job in normal production.

E. No air-conditioner low-speed feeder condition There is no air-conditioner printing room, plus printing conditions with only shallow tray sink and no temperature cooling control, at present, there are few, but there are still some low-speed feeders, fixed at 3000 per hour Because of the slow speed and the constant speed printing, the temperature increase is relatively small, which is relatively easy.

However, the surface of such printing cylinders is large, and the models are relatively open. In particular, the distance from the wet water roller to the ink roller is wide, and the distance from the last ink roller to the blanket cylinder is also long. Therefore, the cause of the change is also more. Power saving and heat dissipation often cause the printing press to move to the window under such conditions, but it often causes changes in morning, afternoon, and evening sunshine, and there is a difference in color temperature and illuminance. At the same time, the wind blows out of the window. Because it is also another unpredictable failure factor.

In addition to the environmental factors, materials, printing quantity, printing machine conditions, printing speed, and other factors mentioned above, the adjustment mechanism for the water supply volume of the printing press itself and the continuous or intermittent water supply mode will produce water at the same scale due to different speeds. There are inconsistencies.

4、A variety of water supply mode classification A, scale A section of water supply to adjust the scale or number of teeth of a section of water supply, is used to transfer water roller water supply method, this is only suitable for use in low speed type gearless lithography machine, due to outside In the environment and paper changes to increase or decrease the processing of teeth, but in the increase of the two teeth scale water shortage, increase the three teeth scale water quantity and too much enthalpy situation, can still use the scraper response. If you use a variable speed lithography machine, most of the low-speed water is insufficient and the high-speed water is too much. The reader will have doubts that the high-temperature temperature rises to increase the evaporation of water, and how high the amount of water at high speed will be?

There are two factors that increase the amount of water: one is the transfer of the water roller, the slow speed of printing at low speed, inertia is small, so the inertial force when it is in contact with the sink roller is very small, drag only half gear, otherwise the speed from 3000 to 6000 When the original three-toothed scale was set, the inertia may become larger and the sink roll may be dragged by 1.5 teeth. Then, the moisture content is more than 30%. Originally, the printing speed is doubled and the water is doubled. The printing surface has as much evaporated water. The moisture content is already too large, and now it has increased by 30% due to inertia. Therefore, some mechanical stones are designed to make contact with the front roller deceleration function to create a gentle inertial effect.

Another factor is the sink roller. The water film on the low speed running sink roller is thin. The water film with high speed due to the running of the sink roller is thicker, and at least more than 60% when the speed is doubled. It is also an additional cause of control, and one of the main causes of the increase in water content during high-speed printing.

B. The independent motor controls the continuous supply of water and the two-stage independent motor controls the water supply. If there is a cooling system for ink and feed water under good constant temperature and humidity, then there is almost no need to regulate the water supply because, It is used to calibrate the quantitative water supply. Some printing presses have recently increased the school edition to 7,000 sheets per hour. This is not the maximum printing speed of 1,6000, which is a quarter of 4,000 sheets. In the unlikely event of a paper feed, Feida still “slows” at nearly half the speed. This two-stage high-speed section is often adjusted on the discharge plate with a rotary knob or control panel in a digital manner. If there is a dry spot, just turn the knob to the end to provide quick water supply. Just focus on the high-speed water supply button.

C, curve set water supply continuous water supply, speed tracking curve setting method, and the above B is very similar, but the press can set its own speed and water supply relationship H, M, L and other curves, H The difference between high and low speed water supply is the largest. The low speed water supply starts at a low point. Its highest point may be 1.5 times the water supply at a low point. The operator selects the appropriate curve to perform the water supply according to the paper and weather conditions (humidity is the main factor). When the speed changes, it can increase or decrease the water supply according to the curve change. As long as it uses programs, this is one of the most ideal ways.

D, perceptual water supply-sensing water supply methods are also based on continuous water supply, but there are infrared or other ways to sense the thickness of the printing plate surface water, feedback to the continuous supply of water to the drive motor to adjust the water volume changes, although ideal, but so far Still not popularized practically.

5. The need for safe water supply and its cause Because the logic of safe water supply cannot be eliminated in the driest zone, the “dryest” zone should be kept in sufficient water to keep the printing plate clean. The section with more water supply may have more than 40-50% of the water, so if you want to dry too dry and not too dry spots, and you can not have too much emulsification to make the ink drop sharply or produce water droplets white spots, then this It is necessary to keep the pressure of the water roller uniform and adjust the appropriate amount of the small roller. The surface of the water roller should not be stained with ink as much as possible, so that the printing plate is very clean and evenly watered from left to right.

In the old-fashioned water supply system, sometimes the water was not enough, the operator had an emergency remediation method for adding water to the area. In the past, the sponge was used to sway the water, and then the plastic oiler was used to make up the water, but the water was often lost between the sprinkler and the water droplets. Causes water or acid-containing water to splash on the bearing or bearing seat of the water roller. This part of the machine is easily rusted and worn and loosens. If the water supply on the operating side is normal, the water supply on the drive side is insufficient, plus the drive The existence of motor, pump, and frozen wet water mechanism also makes it easier for the temperature to rise and the evaporation to increase. As a result, the ink balance between the operating side and the driving side is further increased.

Therefore, it is necessary to add maintenance, repair, or pay attention to the auxiliary spraying of water droplets. If the use of waterproof butter is applied in advance, it will still prevent rust and prevent loosening. However, most of them use continuous water supply, and there are independent motor-driven sink rollers. The increase in water supply can be independently accelerated by the control button. It does not cause loosening of water droplets due to erroneous spraying, and there is a lot to maintain the uniformity of water supply over the entire surface. Great benefit.

The surface of the water roller is easily deformed due to the action of alcohol and moist water. This means that for rolls without water fleece, precise diameters are required to maintain the overall uniformity of water supply in order to maintain the uniformity of the water or the area. Some water roller materials have long-lasting durability up to two