3 Ink and ink Water and ink are the conditions on which the quality of printing depends, and the best water-ink balance can ensure the reproduction of the gradation, color reproduction and good definition of the printed product. Once the water and ink balance is destroyed, a series of printing failures will occur. It is very important to grasp the balance of ink and wash, but it is also the most difficult. There are dedicated water supply and ink supply mechanisms on the printing presses. Their working conditions have a direct impact on the water and ink balance. Correctly understanding and mastering the working principle of the water and ink mechanism has a positive significance for the realization of water and ink balance. 3.1 Inking mechanism The function of the inking mechanism is to supply ink uniformly, stably and continuously to the surface of the printing plate. The inking mechanism is composed of several parts: the ink fountain and the ink fountain roller, the ink transfer roller, the ink inking roller, the ink leveling roller, the heavy roller, the inking roller and the inking roller's clutch and pressure regulating mechanism. The function and working principle of each part are analyzed in detail below. 1. Ink fountain and ink fountain roller. The function of the ink fountain is to hold ink. The function of the ink fountain roller is to take out the ink in the ink fountain and transfer it forward. The roles of the ink fountain and the roller are interdependent and cannot exist independently from one side, as shown in Figure 3.1. The ink is actually stored in the groove between the ink fountain and the ink fountain roller, and the ink transfer of the ink fountain roller is performed through the gap between it and the ink fountain. The overall function of the ink fountain and ink fountain roller is to supply ink to subsequent ink paths. The amount of ink supply is determined by the graphic distribution on the surface of the printed product. So how to control the amount of ink at the ink fountain roller? According to the schematic diagram, it can be seen that the amount of ink output is related to the gap between the ink fountain and the ink fountain roller. The larger the gap, the greater the amount of ink output; the size of the ink output is also related to the rotation angle of the ink fountain roller. The larger the amount of ink, assuming that the amount of ink output is represented by S, the gap between the ink fountain and the ink fountain roller is represented by T, and the angle of the ink fountain is represented by A, then S = A × T. When the ink output is insufficient, the A value or T value can be increased; when the ink output is excessive, the A value or T value can be decreased. When the ink output is constant, A and T are inversely proportional, that is, A increases, T decreases or A decreases, and T increases can ensure the normal ink output. In normal printing, the ink output S is not allowed to change, that is, the product of A and T is a constant. Can the choice of A and T be arbitrarily chosen according to their inverse relationship? From the perspective of ink leveling, the thinner the ink layer, the better the effect of ink leveling; from the perspective of ink separation, the thinner the ink, the better the separation effect; from the perspective of ink supply control, the thinner the ink, the more control The more sensitive it is. So in a word, try to make the ink layer as thin as possible. Changing the thickness of the ink layer can only adjust T, the gap between the ink fountain and the ink fountain roller. The adjustment can be made by the following jacking wire. The value of T decreases and the value of A must be increased to ensure the ink supply. Therefore, the adjustment principles of the ink fountain and ink fountain roller are: a. The smaller the gap between the ink fountain and the ink fountain roller, the better; The reduction of the gap between the ink fountain and the ink fountain roller is limited, and the smaller the ink is, the more difficult it is. After the size, impurities in the ink fountain can easily block the lower ink, and the increase in the angle of the ink fountain roller is also limited. Therefore, the adjustment principle should be changed to: under the condition of ensuring sufficient ink supply, the gap between the ink fountain and the ink fountain roller is as small as possible, and the rotation angle of the ink fountain roller is as large as possible. Different printing plates require different amounts of ink, and different positions of the same printing plate require different amounts of ink. Therefore, the ink supply of the ink fountain must be adjustable in the axial direction. This adjustment is mainly achieved through different gaps between the ink fountain and the ink fountain roller at different positions, that is, S1 = A · T1, S2 = A · T2, ... Sn = A · Tn. Use a small A value, that is, a small ink fountain roller angle, and adjust T1, T2, ... Tn, and then increase the A value uniformly to achieve the required ink supply. If you use a larger A value (that is, a larger corner) at the beginning, it will cause too much ink drop, and it is very troublesome to remove these excessive ink amounts. For places that do not require ink, ie S = 0, how to adjust it? Since the A value is common, the T value can only be reduced to zero. It is difficult to strictly reduce the T value to zero. If you are a little careless, the ink fountain and ink fountain roller will rub against each other and scratch the surface of the ink fountain roller, so you ca n’t reduce the T value here to zero, but it can only be slightly larger than the zero value, there is a layer of ink on the ink fountain roller Just a film, this layer of ink film can actually play a role in lubrication. The rotation of the ink fountain roller is driven by a set of link mechanisms. However, the tensile strength of the connecting rod is limited after all. If the T value becomes a negative number, one or both of the connecting rod and the ink fountain roller must be damaged. Usually, the indentation will be left in the circumferential direction of the ink fountain roller. 2. Ink transfer roller. The function of the ink transfer roller is to transfer the ink on the ink fountain roller to the ink cross roller (or uniform ink roller). Because the ink layer on the ink fountain roller is unevenly distributed along the axis, this causes great difficulty in transferring ink. The thicker the ink film, the worse the uniformity. Therefore, from the perspective of ink transfer, the ink film of the ink fountain roller is also required to be as thin as possible. Each part of the ink transfer roller must be taken care of during ink transfer. This can only be achieved by increasing the contact pressure. The pressure between the ink transfer roller and the ink fountain roller is controlled by a spring, which can be adjusted by adjusting the spring force. To change the pressure. However, the pressure should not be too large, and excessive shocks will occur at the moment of contact with the ink fountain roller. The pressure between the ink transfer roller and the ink transfer roller can also be adjusted, but it must be noted that the pressure should be as consistent as possible to achieve uniform ink delivery. [next] 3. Ink roller. The function of the ink inking roller is to distribute the ink in both circumferential and axial directions. Only in this way can we ensure that the ink volume of the printing plate is always uniform, and the effect of the cross-inking effect directly affects the uniformity of the ink on the printing plate. The following detailed analysis of its ink-crossing process. The ink roller moves from left to right and from right to left. At the switching point from left to right or from right to left, the speed of the axial movement of the ink inking roller must be zero, so no ink inking can be performed at these two points. In the process from left to right or from right to left, the speed of the axial movement of the ink fountain roller gradually reaches the maximum from zero, and then gradually decreases from the maximum to zero. The higher the speed of the shaft string, the better the effect of ink string. Obviously, the ink in the middle is the best. The tandem roller's tandem movement is generally achieved by an eccentric wheel driving the pendulum mechanism, so its speed change is approximately sinusoidal, as shown in Figure 3.2. An ink reciprocation can be divided into six areas. Obviously, the ink inking area 2 and 5 are the best, and the ink in the other four areas are similar. Therefore, in the printing process, the area 2 and 5 should be used as much as possible. In two places, the outer circle of the plate cylinder is flattened, as shown in Figure 3.3. Obviously, there is no need to transfer graphics in the gap of the printing plate, so the place has the lowest requirements for cross-inking. Graphics and text should be transferred on the surface of the printing plate, which has the highest requirements for ink-crossing. Connect the requirements of the ink on the surface of the printing plate to the effect of the ink on the ink roller: the left and right reversal points of the ink roller should be carried out at the gap of the printing plate, and the place with the largest amount of ink ink should be related to the printing The effective parts of the effective parts are printed relative to each other. If the graphic on the printing plate is close to the first half of the printing plate, the reversing point of the ink inking roller can be moved to the trailing position of the printing plate, so that when reaching the printing plate, the ink inking roller is already in zone 2 and 5. Zone, if the effective part of printing is in the trailing edge, you can place the reversal point on the gripper of the printing plate. When the trailing edge is reached, the ink inking of the inking roller is already in Zone 2 or Zone 5. It can be seen from the above analysis that the change of the ink volume of the ink inking roller directly affects the uniformity of the ink on the printing plate. The reversal point can only appear on the non-printed parts of the printing plate, generally in the gap of the printing plate. It can be seen from this that the inking cylinder turns from left to right and the plate cylinder rotates one circle; from the right to left, the inking cylinder rotates one more round. In other words, the inking roller traverses back and forth for one week, and the plate cylinder rotates twice. A large amount of ink-crossing of the ink-crossing roller is good for ink-crossing, but the amount of ink-crossing should not be too large because the axial motion of the ink-crossing roller actually relies on friction to evenly distribute the ink. The friction will generate heat, the temperature will increase, the viscosity of the ink will decrease, the print will be easily deformed, and it will easily cause the emulsification of the ink. The greater the amount of ink inking, the worse the unevenness of the distribution, as shown in Figure 3.4. Therefore, the amount of ink crossover is not easy to be too large. If the ink volume is too small, the ink can not be opened axially, and it can not play the role of ink distribution. Therefore, the ink volume must be moderate. From the perspective of the ink roller and ink, the thinner the ink layer, the easier it is to even out. The amount of ink inking is directly related to the picture and text. The smaller the area of ​​the picture and text, the smaller the requirement of the ink flow; the larger the area of ​​the picture and text, the greater the requirement of the ink flow. Therefore, the amount of ink crossover required for the bright tone part is small, the amount of ink crossover required for the dark tone part is large, and the amount of ink crossover required on the ground is the largest. When printing packaged products, especially when printing some lines, sometimes it is necessary to print several colors on a color group at the same time. At this time, the cross-linking of the ink-crossing roller cannot be allowed, that is, the cross-talk is adjusted to zero. At present, most of the ink inking on the machine uses reverse ink inking, that is, the ink inking rollers go from top to bottom, one to the left and one to the right at the same time. The result of such a string is that the maximum dots and the minimum dots overlap, and the effect of the ink string is not good. If their maximum points cross each other and their minimum points cross each other, the ink leveling effect is better. This is the so-called phase cross-inking. The roughness requirements of the ink roller surface are very high. If the surface beats too much, the blackening effect will be significantly deteriorated. The surface accuracy of the ink roller is an important standard for inspection before leaving the factory. In general, it must be processed by a grinder. Ink transfer rollers pass ink, not water, so the surface should be oleophilic and water-repellent to prevent water from returning to the ink path and causing emulsification of the ink. 4. Leveling roller. The ink leveling roller has the following functions: (1) Evenly distribute ink in the circumferential direction This is the main function of the ink leveling roller. In theory, the thickness of the ink layer transferred to the surface of the printing plate should be uniform. This requires that the ink be smoothed in both the axial and circumferential directions. (2) Transfer ink and change the ink path to distribute the ink roller as a bridge between the ink rollers, naturally it should play the role of ink transmission. The greater the number of rollers, the less ink is distributed to each roller, and the fewer the rollers. The more ink that is distributed to each stick, the effect of changing the distribution of the ink path can be achieved by changing the number of ink leveling rollers. (3) It can compensate for the processing and installation errors of the ink roller. The ink rollers are rubber rollers. When they are under pressure, they can closely contact with other hard rollers to complete the transfer of ink. (4) Buffer vibration absorption Because of the unevenness of the surface of other hard rollers, there is vibration on the surface during movement, and the results of these factors are converted into the elastic energy of the ink roller, which is generated when contacted and released when detached, thereby putting the vibration And shock was absorbed. (5) Safety function Because the surface of the ink leveling roller can be compressed and deformed, when a foreign object enters the ink path, the surface of the ink leveling roller is greatly deformed, while the surface of other hard rollers is not deformed, thereby avoiding damage to the hard roller. The movement of the ink leveling roller is driven by the friction of the ink roller. From the perspective of ink transfer, there should be no slippage in the place where it is relatively in contact. That is, the maximum static frictional force of its rotation should be much greater than the frictional resistance or ink viscosity that hinders the rotation of other parts. 5. Heavy roller. The role of the heavy roller is: (1) Make reliable contact between the ink leveling roller and the ink cross roller. In fact, the heavy roller presses on the surface of the ink leveling roller, and the vibration energy of the ink leveling roller is transferred to the heavy roller. Due to the heavy weight of the heavy roller, its speed is very small, which is in accordance with the law of energy conversion, as shown in Figure 3.5. It can be clearly seen in the actual process that after the heavy roller is installed, the vibration of the ink roller is significantly reduced. (2) Change the role of ink path and ink distribution. This effect actually exists with the ink leveling roller, as shown in Figure 3.6. The heavy roller on the left is not in the ink transmission line, so it can only change the ink distribution. The right roller is located in the ink transmission line, so it plays a role in changing the ink path. Since the heavy roller participates in the ink distribution and transfer process, it is not allowed to destroy the uniformity of the ink. From this point of view, the heavy roller surface must be clean. [next] 6. Inking roller. The inking roller has the following four functions: (1) Supplying ink to the plate cylinder This is one of the most basic functions of the inking roller. During printing, the ink on the printing plate is continuously transferred to the paper. If no ink is supplied subsequently, printing cannot proceed normally. In fact, as much ink is missing on the plate cylinder, the inking roller should replenish as much ink, so it can also be said that the inking roller plays a role in making up for the loss of ink on the plate. (2) Make up the unevenness of the surface of the printing plate and the surface of the inking roller. If the inking roller cannot be in close contact with the two, the ink cannot be transferred well. The uneven deformation of the surface of the rubber roller must be used to compensate for its unevenness. (3) When the damping vibration absorption ink roller is in operation, it receives the force from both the ink roller and the printing plate. The force of the printing plate on it is constantly changing. In addition to the force generated by the unevenness of its surface, and each time the position of the notch and non-notch is exchanged, the impact is the largest. The tandem and tandem of the ink roller will cause the ink roller to vibrate. These forces continuously transfer energy to the inking roller, which in turn continuously absorbs and releases it, thereby acting as a shock absorber. (4) Safety effect When a foreign object enters between the inking roller and the printing plate, the deformation caused by the foreign object becomes the deformation of the surface of the inking roller, while the other surface is not damaged, so it plays a safety role. There are generally more than two inking rollers, and four are currently popular, so does each one have the same effect? Practice has proved that it cannot be the same. If the diameter is the same, as shown in Figure 3.7, the ink sticks will appear at the same place in the circumferential direction of the printing plate when the four ink sticks are inked. If the amount of ink on each stick is the same, that is, the amount of ink on each stick is 25%, it cannot play a complementary role, because from the perspective of the printing plate, the ink on the surface must be uniform. Therefore, inking on the printing plate should be able to play the role of inking and leveling, which is exactly the same in the actual process. The amount of ink supplied by each inking roller can be determined by the ink separation rule. The separation rule of ink is more complicated, but it is transmitted in order in the ink path approximately according to the principle of "half meeting". According to this rule and the arrangement diagram of the ink path, the inking amount of the inking roller can be obtained. As shown in Figure 3.8, it can be seen by calculation that the amount of ink applied to each root is different. The first and second roots are 42%, and the third and fourth roots are 80%. It can be seen that the first two rollers mainly play the role of inking, they provide 84% of the ink demand on the printing plate, and they are called the main inking rollers. The last two rollers have a relatively small amount of ink, mainly for the purpose of ink leveling, more precisely, more replenishment and less replenishment. This is because the ink layers on the first two rollers cannot be completely consistent after the ink is applied. Some places are less than 84%, some places are greater than 84%, and some places are even greater than 100%. Less than 84% need to replenish ink to reach 100%, and more than 84% and less than 100% also need to replenish ink to reach 100%, but only a little less. No more than 100% of the ink can be refilled, and the excess ink should be recovered. If it is more finely divided, the main function of the third inking roller is to assist ink supply (filling level), and the fourth roller is mainly used to stop ink, level ink, and collect ink. This is more prominent in the modern popular Mo Lu. The inking volume of the first and second rollers is 44%, the inking volume of the third roller is 9%, and the inking volume of the fourth roller is 3%. 7. Ink roller adjustment. The adjustment of the inking roller is very important, because it is directly related to the transfer of ink, and once an error occurs, it cannot be compensated. So how to adjust the inking roller? If a round roller is placed on a flat surface, as shown in Figure 3.9. Obviously, no matter what angle the round roller is placed with the plane, as long as it is in the plane, its contact state with the plane is the same, it can be said that it is not sensitive to changes in position. If the lower plane is changed into a cylinder, as shown in Figure 3.10, when the position of the round roller changes on the upper side, the sensitivity is higher than that of the plane, but as long as the position is not far apart, it can be said that the sensitivity is still very low . If the large cylinder is changed into a small cylinder, as shown in Figure 3.11, when the position of the roller changes, its sensitivity to the position increases significantly, and some places are out of contact. The results of the above analysis are applied to the inking roller, inking roller and plate cylinder, as shown in Figure 3.12. It can be seen that the sensitivity between the inking roller and the inking roller to position changes is high, while the sensitivity between the inking roller and the plate cylinder to position changes is low. In terms of installation requirements, the axis of the plate cylinder and the axis of the inking roller are still parallel. If the contact relationship between the inking roller and the inking roller has been adjusted, the contact relationship between the inking roller and the plate cylinder can also be guaranteed, and vice versa. However, due to sensitivity, the axis of the inking roller is probably not completely parallel to the axis of the plate cylinder, and therefore cannot be parallel to the axis of the inking roller. Therefore, when adjusting the pressure, you must first adjust the pressure between the inking roller and the inking roller (raise the ink landing gear), and then adjust the pressure between the inking roller and the plate cylinder (put the ink landing gear down). This is exactly what is required. The eccentric mechanism is used to adjust the pressure between the inking roller and the inking roller. At present, almost all machines use the worm gear mechanism to drive the movement of the eccentric wheel (the inking roller is installed on the eccentric wheel). The eccentric wheel must be at the same time to ensure that the axis of the inking roller and the axis of the inking roller are parallel to each other, and can be checked with (0.20mm thick) plugs. An eccentric wheel or other similar mechanism is used to adjust the pressure between the inking roller and the plate cylinder. The pressure exerted by the inking roller on the printing plate depends on the spring and its own ability. At the same time, the spring also plays a role in buffering the vibration absorption. The pressure between the inking roller and the inking roller should not affect each other, but this condition must be established under the premise that the three axes are completely parallel. If the pressure between the inking roller and the plate cylinder is inconsistent, the pressure between it and the inking roller will be affected. (Figure 3.12) There are different opinions on how appropriate the pressure between the inking roller and the printing plate is. However, from an ideal state, it is best to be in line contact, but this is actually impossible, because the imprint must be smooth and smooth. If this is not possible, the printed product looks unrealistic, so there must be some printing pressure. If printing pressure is required, there must be a contact surface. The ink line width is usually about 4-5mm. The movement of the inking roller is driven by the friction between the inking roller and the plate cylinder. If it is not suitable, it may cause a slip on the surface of the printing plate, thereby expanding or sliding the dots. The landing mechanism of the inking roller is to control the clutch between the inking roller and the plate cylinder. The requirements are: when leaving, the distance between all the rollers and the plate cylinder is the same; after closing, all the rollers should also be the same as the distance between the plate cylinder. The position change caused by the ink roller pressure adjustment is small compared with the clutch amount. Some equipment adopts a clutch mechanism. When the amount of clutch is found to be inappropriate, it can be adjusted by the jacking wire on the landing gear. Some equipment uses strict calculations to ensure that the amount of clutch is consistent, but it requires processing and installation requirements. Very high. The ink and wash mechanism must be stable and reliable. When it is time to close, it should be closed when it is time to leave, to ensure the normal operation of the machine. [next] 8. Wiper. The function of the ink scraper is to scrape off the unnecessary ink in the ink path. The squeegee is generally in direct contact with the squeegee roller. Since the squeegee roller is a hard roller, the front opening of the squeegee is made of rubber material, and generally the thick rubber is used, as shown in Figure 3.14. The position and pressure of the wiper directly affect the quality of the wiper. (1) If the position is too high, the rubber cannot reach the ink, see Figure 3.14. (2) If the position is too low, the blanket will bend and the ink will stay on the ink roller, so the appropriate position should be the rubber on the tangent line of the roller. The above points should be considered during the use process. At present, the position of the wiper is generally fixed, and some pressure equipment must be adjusted every time it is used, and some equipment need not be readjusted after being adjusted once. , Very easy to use (this is actually not difficult to do). As versatile in design as in concept, the Variable Balans is the perfect instrument for the ever-changing demands of today's work places and lifestyles. Work becomes a breeze as the upright, "alert" posture promotes concentration and activity. Chairs For Kneeling, Kneeling Office Chair, Kneeling Office Chairs Ningbo YINGBOTE Trading Co.,Ltd , http://www.intelligentoffice-cn.com
(Figure 3.1)
b. The larger the angle of the ink fountain roller, the better.
(Figure 3.2)
(Figure 3.3)
(Figure 3.4)
(Figure 3.5)
(Figure 3.6)
(Figure 3.7)
(Figure 3.8)
(Figure 3.9)
(Figure 3.10)
(Figure 3.11)
(Figure 3.13)
(Figure 3.14)
(3) If the pressure is too large, the rubber will bend and the ink will stay on the roller, see Figure 3.15.
(4) If the pressure is too low, the rubber and the roller will not evenly contact, some places can scrape off the ink, and some places can not scrape down, as shown in Figure 3.15. Therefore, too much pressure or too little benefit.
(Figure 3.15)
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