The Influence of Network Control on Print Quality (2)

10) Effect of ink

1 Select the appropriate ink. The texture of the ink is required to be fine, smooth, good in flowability, proper in viscosity, without the disadvantage of retardation, vivid in color, and the ink is preferably translucent. The cohesive force of the ink with too low fluidity is too strong to be evenly milled, thereby reducing the transferability of the ink; if the fluidity is too large, the adhesion of the ink may be poor, and the printed dots will be flattened, dull, and spread from the base to the periphery. The phenomenon affects the quality of the product. 2 Reasonable emulsification of ink: Compared with offset printing and other printing methods, it is often due to the emulsification of the ink that the color saturation is not enough. Therefore, everyone in the actual production is trying to reduce the emulsification of the ink in order to achieve a more vivid ink effect. . However, the actual situation is that without proper emulsified ink, it can not be well transferred between the ink roller, the ink roller and the printing plate, and between the printing plate and the blanket. (The reason is that water forms a water film on the ink surface and hinders the ink transfer. ), the direct consequences will lead to the deformation or emptiness of the outlets. The ideal emulsification value is kept at 26%. However, if the emulsification value of the ink exceeds 30%, a clear boundary between the water film and the ink film will be lost, and edges, blurs and the like will occur at the edge of the dot. The more serious consequence is that the pigment particles in the ink are precipitated from the resin. The accumulation of blankets on the plate will also affect the ink transfer.

11) Influence of pressure

The pressure should be based on the premise that the printed materials have strong dots, clear graphics, vivid colors, and adequate darkness. The excessive pressure causes the ink on the printing plate dots to spread and deform under the pressure; the small pressure will directly lead to ink transfer. The rate drops and the ink transferred to the substrate is small and thin. However, if substrates with relatively smooth surfaces (such as textured paper, embossed paper, and newsprint) are used, the printing pressure must be increased to compensate for the unevenness of the surface of the substrate and improve the ink transfer efficiency so as to ensure the transfer of dots. Under the premise of ensuring the quality of the printed matter, the smaller the amount of pressure applied, the better. In addition, the impact on the outlets is also affected by the pressure of the water roll. The pressure of the water roll can only make the water transfer to the printing plate smoothly and evenly. The pressure is too large or too small to find the printing unfavorable. When the pressure is too large or too small, it is unfavorable for printing. When the pressure is too high, it will cause the water roller to jump at the mouth of the mouth and cause friction. Under the pressure of the water, the mesh point will be squeezed smaller or deformed. Of course, the consequences of too little pressure are obvious, and the amount of water cannot be transmitted normally. 2 The effect of the ink roller pressure: The ink roller pressure should be flat and light, the pressure is excessive, the network points are easy to press and paste, affecting the quality of the printed product.

12) The effect of ink and water balance

Controlling the balance of ink and ink can improve the quality of printed products. Avoid large ink and large ink during offset printing. Too thick ink layer will cause dot gain, control 3% to 5% bright tone area, small dot is not lost, 5% middle tone dot does not expand, do not stretch, dark tone area 95 The large network of 97% to 97% is not ambiguous. The control standard for the amount of ink is as follows: the network of points is solid and clear, and the ink hue of the ink is printed with as little ink as possible.

13) Influence of Plates

1 The printing plate coating glue should be thin and even. If the glue is too thick, it will not be easy to clean after drying, and it will easily damage the dot. 2 When the printing plate is not in use, try not to place it in the sun. If you shut down for a long time, you should pay attention to the protection of the coating glue. When cleaning the printing plate, be careful not to scratch the printing plate. 3 When the machine is down for a long time, care should be taken not to place the long roller directly on the plate, and to prevent the plate from being damaged due to prolonged contact with the fountain solution. The failure of these tasks will have a great impact on the printing sites.

14) Printing presses and other effects

1 The normal working condition of the printing machine: to ensure the normal working condition of the printing machine is the key to the printing and copying outlets. In a normal printed matter, a dot gain of approximately 15% occurs due to a normal embossing or the like, which is a normal phenomenon and compensation can be made during prepress processing. However, when the printing machine is abnormally vibrated, for example, due to improper meshing of the printing roller gear, excessive clearance between the roller bearing and the bearing pad, excessive printing pressure, and bouncing of the water roller and ink roller, etc., this can cause dots in the printing process. Transmission occurs when the dot deformation (this deformation may be a dot increase, or simply the shape of the dot changes), resulting in overlapping changes in the dot, an abnormal jump in density. Changes in these outlets will directly lead to failures such as bars, ghosting, merging, and loss of outlets. 2 Sanqin: In the operation of the machine, it must be ensured that Sanqin is used to mix the ink fountains (guarantee certain fluidity of the ink), and the printing samples (based on the amount of ink used on the proofs) are used to proofread the ink on the prints. , Observe the amount of water on the ground (this is the constant monitoring of the water control we mentioned earlier). These operations can better ensure the transfer and reproduction of outlets during the printing process.

3 Dot distortion compensation

Dot distortion has a great influence on the entire copying stage of a print. However, when we can more accurately predict the changes in the transmission of outlets between devices, we can effectively compensate for the changes that will take place before the outlets change before the outlets will undergo changes. This requires us to conduct data management, standardization, and standardized management. For example, through data detection on the processes and equipment used by us, and understanding of the basic data for each process, we can consider it comprehensively at the beginning of the process setting, taking into account network change factors caused by technological reasons, and make network point compensation. Settings. For example, the following changes occurred in the copy process of a certain print product: the copy of the positive image network was reduced by 2%; the sunburn spot was reduced by 4%; the printing network was increased by 15%; and the optical point was increased by 12%. After addition and subtraction of mathematics, we will find that as long as the network points are pre-compensated by 21% before the network starts to transmit, we will just get the effect we want after delivery. Although the actual dot compensation is not as simple as mentioned above, this compensation and dot change is not just a linear relationship, and different percentages of dot changes in the replication process are not the same. The operator only needs to inform the software of the changes that will occur at the outlet (typically, the rate of change of the outlets at 50%), and the computer can compensate the entire printing system according to a certain algorithm.

In short, due to the numerous process links involved in the transmission of outlets, the quality of the outlets directly affects the reproduction of the print and the level of printing. Therefore, it is necessary to control every link in the entire printing process to avoid network reduction or to reduce the number of outlets as much as possible. The degree of reduction. This requires truly standardization of management and standardization of operations. Only strict implementation of management standardization and standardized and data-oriented operations will be possible in image processing and network point compensation before printing.

Source: PACK.CN Author: Xia Bin