First, the classification of the lining Offset printing plate cylinder and blanket cylinder (rubber roller) surface lining, blanket cylinder roller lining can generally be divided into the following three categories. 1, hard pack liner Generally, a few sheets of paper under the blanket constitute a hard lining. This kind of lining is relatively hard, the elastic modulus of the lining is large, and a small amount of deformation can produce a great printing pressure. Therefore, the use of this type of lining reduces the amount of compression of the lining, that is, the amount of deformation of the lining is small, and the dot enlargement and deformation are also small. Therefore, the hard lining is better for the transmission of dots, which is conducive to the reproduction of color and gradation, and is suitable for the printing of reticular prints. However, special attention should be paid when using such a lining. The lining compression should be controlled within 0.2mm, preferably around 0.1mm. If the compression of the lining is too large, it will not only be detrimental to the machine, but will also cause other failures, and it will also be bad for the transmission of the dots, losing the advantage of using a hard lining. Therefore, the use of rigid lining requires high precision of the machine and accurate printing pressure adjustment. Otherwise, it will not only reflect the advantages of rigid lining, but will also bring about new shortcomings. In other words, the rigid bag is lined with its unique conditions of use and application and cannot be used everywhere. At present, it is unscientific for some printing companies to blindly use hard liners. 2, soft lining The soft lining is generally under the blanket and it is added with several thin papers. The software lining is just opposite to the hardware lining. Its elastic modulus is small, and the lining compression required to produce the same printing pressure is relatively large. Generally, the compression amount is controlled between 0.2mm and 0.3mm. The soft lining has less transmission to the dots, but the contact area is wider when the soft lining is imprinted, and the contact is relatively good. The ink is relatively full and full, especially when it is printed in real products. It is suitable for printing text, color blocks, field prints. In addition, the soft lining cushioning ability, the blanket is not easy to crush, and the machine accuracy and printing pressure adjustment accuracy requirements are relatively low, so the soft lining is suitable for use on the old machine or the new machine with low precision . 3, neutral packing Neutral lining is generally composed of rubber blanket under the blanket, its elastic modulus is centered, so its performance is also in the middle, and its use occasion is also in the machine between the new and old machines alternately stage, can also be used on new and old machines, This kind of lining is more general, and the performance is also OK. Second, the determination of roller lining The determination of the lining category can be determined according to the above description. The following principles should be taken into account in determining the total lining thickness: 1, determine the principle 1 No relative sliding principle on the drum surface (synchronous rolling condition) The offset press has three rollers for each color group. When printing, the three rollers are in contact with each other. To ensure the product quality and other requirements, it is required that the roller contact surface be a pure roller. There can be no relative sliding friction, but because the three rollers are through gears. The angular velocity of the transmission is equal. To ensure that the surface does not slide, the rolling radius (rolling R) of each roller is required to be equal. When the drum is a rigid body, the rolling radius of the drum is equal to the free radius of the drum (R-self), and the blanket cylinder is provided with an elastic wrapping, which cannot be treated as a rigid body. The impression cylinder and the printing plate cylinder can be regarded as a rigid body, so the blanket The rolling radius of the drum is not equal to the free radius of the drum. Studies have shown that the rolling radius of the elastic roller is related to the amount of compression of the lining on the elastic roller. The general relation is as follows: R roll = R from + λ, λ is the compression amount of the elastic roller. 2 Circular roller tangential cutting principle (central distance condition) Between the rollers on the offset press, power is transmitted through the gears. To ensure the smoothness of the transmission and reduce the wear of gears, it is required that the gears mesh in tangential engagement with the pitch circle, that is, the center distance between the rollers is the index of the two roller gears. with. However, in practical applications, some people tend to adjust the center distance of the drum too large, resulting in a large gear meshing backlash, a drastic reduction in the smoothness of the transmission, and aggravation of gear tooth wear. This will not only reduce product quality, but also reduce the product quality. Reducing machine life is a problem that should be worth paying attention to. 3 pressure suitable principle The contact pressure between the plate cylinder and the blanket cylinder is called the platen pressure, and is represented by λp. The contact pressure between the blanket cylinder and the impression cylinder is called the printing pressure, that is, the printing pressure, which is expressed by λi, and the printing pressure is generally required. Pressure greater than the plate pressure 0.05mm ~ 0.1mm. The appropriate pressure is the first principle to determine the drum liner. With regard to stress, special attention should be paid to preventing excessive pressure. Some people will increase their pressure blindly when they encounter problems, and the pressure will become too large. The edition pressure is most sensitive to dot gains, and the edition pressure has caused the dot expansion to be serious, which has affected the color and level reduction of printed products. 2, determine the method The above principles cannot be met at the same time. In practical applications, only some of the conditions can be satisfied, or the above conditions can be satisfied as much as possible so that the difference is not too great. The specific determination methods are as follows: 1The lining determination method emphasizing synchronous rolling conditions This method can meet the simultaneous rolling conditions under a fixed paper thickness, but does not meet the center distance conditions, such as paper thickness changes, does not meet any conditions, so this method is only applicable to the case of long-term printing fixed thickness paper products. Set the paper thickness to h, the platen pressure to λp, the press pressure to λi, λp, and λi. Set the specific data according to the type of lining beforehand. Hard lining: λp=0.1mm, λi=0.15mm, software package lining: λp = 0.2mm, λi = 0.25mm, neutral liner: λp = 0.15mm, λi = 0.2mm, according to the synchronous rolling conditions: RP roll = RB roll = Ri roll, can be derived as follows: RP to =Ri+h Plate cylinder lining is δp = RP from -Rp RB from = RP From - λ λ can be replaced by λp Calculate λ = λp Rubber roller liner δB=RB self-RB Plate-rubber roller center distance A (PB) = 2R B from + λ - λp = 2R B from the rubber-embossing cylinder center distance A (IB) = 2R B from + λ - λi ≈ 2R B since Plate-rubber pillow clearance H (PB) pillow = A (PB) - RP pillow - RB pillow Rubber-embossing roll gap H (IB) pillow = A (IB) - RI pillow - RB pillow From the above computer formula, it can be seen that δP and δB are all functions of paper thickness h. When h is changed, the thickness of the lining is changed. In actual production, changing the paper lining when changing the paper thickness is inconvenient, so the bag determined by this method is determined. The lining data is applicable to the case where the paper thickness is fixed or the paper thickness does not change much in the long-term or most cases. In addition, we can see from the formula that the roller center distance A (PB), A (IB) is approximately 2R B since, very close to the sum of the two roller indexing circles, that is, the center distance condition is approximately satisfied.