How to solve the problem of paper sticking rubber

How to solve the problem of paper sticking rubber in small offset press

in the offset printing process, paper sticking rubber refers to the phenomenon that the surface fibrous substances of paper are adhered to the surface of blanket by ink in the printing process. This phenomenon is relatively common. Generally, paper adhesive rubber appears when printing, which significantly improves the comfort, reduces the material consumption, and when the full plate is on the spot and the amount of ink is large, especially when printing coated paper, when the ink layer of the print is thick and the amount of ink is large, the phenomenon of paper adhesive rubber is easy to occur. It affects the reproduction of pictures and texts and the integrity of points of printed products, making printing impossible, and printing ink paste flowers, resulting in waste products. If it is not found in time, the blanket will be depressed or the paper adhered to the surface of the blanket will be transferred to the ink roller through the plate cylinder, so that the printed matter adheres to the paper scraps and ink residues, and the printing will be interrupted. Improper adjustment of the paper delivery mechanism of the offset press is one of the reasons for paper sticking rubber. There are also the following aspects

1. The biting force of the paper teeth of the imprint cylinder is not enough

when offset printing, especially printing thick and high-grade coated paper, textured paper, offset paper, etc., when encountering large field area, large amount of ink is used, the ink layer is required to be full and thick, and the paper is prone to stick to rubber, which is mainly caused by the insufficient biting force of the paper teeth of the imprint cylinder

solution: the insufficient bite force of the paper teeth of the imprint cylinder will cause the problem of inaccurate printing overprint. Increase the bite force of the paper teeth of the imprint cylinder. You can use the bite force of the paper teeth to make the bite force of each paper tooth uniform. If the overall biting force is still insufficient, the strength of the support springs on both sides can be increased; If the bite piece or the paper adhesive rubber caused by the too smooth pressure pad on the 300 ton tensile testing machine can be solved by sticking fine gauze on the tooth pad to make the bite paper tooth pad rougher, then the paper can be bitten, so as to prevent the insufficient bite force of the bite paper tooth from causing the paper adhesive rubber failure

2. The handover time between the paper teeth of the drum and the paper receiving teeth is incorrect

in the offset printing process, there must be a certain handover time between the paper teeth of the drum and the paper receiving teeth from swinging the paper teeth to completing the printing process, and then to the paper receiving teeth, so as to ensure the accuracy of overprinting and the continuity of the paper transmission process. At this time, if the handover time between the paper teeth of the drum and the paper receiving teeth is too short, the handover time is too early If it is too late or incorrect, it will lose control of the paper in an instant, causing the paper to stick to the rubber

solution: adjust the position of the tooth opening plate at the joint of the paper receiving teeth and the roller teeth, and control the handover time between the two within the range of 3 ~ 6mm based on the principle of not biting and tearing

3. The biting force of the paper receiving teeth is too light

when the paper receiving teeth bite the paper, the rear end of the paper does not separate from the drum, and the paper will still be in the rolling state. If the biting force of the paper receiving teeth is small, it is impossible to bite and bite the paper, and the rear end of the paper is easy to adhere to the surface of the blanket, which will also cause the paper to stick to the blanket

solution: the biting force of the paper receiving teeth depends on the elasticity of the four support springs on the paper receiving teeth shaft. If the biting force of the overall paper receiving teeth is too light, the four support springs can be pressed at the same time to increase the biting force, and then adjust the biting force of each tooth. Stretch 60g/㎡ kraft paper into the teeth and pull it out for testing, so that the biting force at the middle and both ends of the tooth row is uniform. If the biting teeth or tooth pads are too smooth, resulting in paper sticking rubber, The fault can be eliminated by sticking fine gauze on the tooth pad or adhesive tape on the bite pad

4. The pressure between the rubber drum and the embossing drum is too high

in the offset printing process, the excessive printing pressure will cause the paper to stick to the blanket. When the fault occurs, even if the biting force of the drum biting teeth and the receiving teeth is increased, this phenomenon occurs from time to time, especially in the case of thick printing ink layer and smoother coated paper on the paper surface. At this time, the friction tension caused by the excessive printing pressure is greater than the biting force of the biting teeth, This reason causes the paper to stick to the blanket, which makes the paper adhere very firmly to the surface of the blanket, and it is very difficult to tear the paper by hand, which indicates this reason

solution: the whole offset printing process is to solve the contradiction between ink and paper. If you want to transfer the image and text coated with a certain thickness of ink on the printing plate to the printed paper, you must apply a certain amount of pressure in the image and text transfer process. People often say that "no printing without pressure" fully illustrates the importance of printing pressure

since the printing pressure is so important, is it the greater the pressure, the better? Of course not. Generally speaking, whether the printing pressure is appropriate or not is often shown by the printing quality of the printed matter. The printing pressure should be based on the premise that the printed matter is a little strong, the graphics and texts are clear, the color is bright and the shade is appropriate, and the smaller the application is, the better

in order to avoid the paper sticking rubber caused by excessive printing pressure and make the printing point clear and complete, the minimum pressure should be used and neutral and soft lining materials should be selected

5. The positioning of the receiving teeth shaft is incorrect

generally, the positioning of the receiving teeth shaft of the offset printing machine is basically correct before leaving the factory. However, there will inevitably be some errors in the processing of the receiving teeth row shaft head cover. In the process of adjusting the paper receiving teeth, it is impossible to keep the position of each row of paper receiving teeth consistent with the tooth pad. When it intersects with the paper receiving teeth of the embossing cylinder, it reflects that the distance between the paper receiving teeth and the front edge of the embossing cylinder is inconsistent. If some distance is too large, it will cause the paper receiving teeth to bite the paper or bite the paper too little, resulting in paper sticking rubber

solution: for the paper receiving teeth with incorrect positioning, it is necessary to replace the new shaft head cover and reposition it by the operator through the routine maintenance of the material change testing machine. For the paper receiving teeth and tooth pads with improper adjustment, they should be readjusted to make each row of tooth pads on the same parallel line

6. Paper adhesive rubber caused by high viscosity of ink

the viscosity of Y, m, C and BK four color common inks overprinted by offset printing is BK> C> m> y, the viscosity of black ink is high, and the viscosity of yellow ink is the smallest. Therefore, when offset printing darker color inks, due to its high viscosity, paper adhesive rubber failure is easy to occur

solution: ① in order to make the ink have good printability, it is often necessary to add some auxiliary materials to adjust the viscosity of the ink according to the requirements of the print. 6 ＃ inking oil can be added. 6 ＃ inking oil is an oily fluid substance with a certain viscosity and yellowish color obtained by heating and refining dry vegetable oil. 6 ＃ inking oil can play two roles: A, it plays a dilution role in the ink; b. It plays a role in reducing the viscosity of the ink. When 6 inking oil is added to the ink, it reduces the viscosity and concentration of the ink, increases the fluidity and paintability of the ink, and enhances the printability of the ink

② add debonding agent in the ink under the guidance of Canadian Standards Association. Debonding agent is a mixture of wax paste, which is an auxiliary material to adjust the viscosity of ink. Without increasing the fluidity of the ink, it can reduce the viscosity of the ink and shorten the silk head of the ink

to sum up, the failure of paper adhesive rubber is caused by many factors. The problem of paper sticking to rubber in work should be comprehensively analyzed and treated differently. In addition to the faults in the paper feeding, receiving and transmission of offset press, the poor printability of raw material paper and ink is also one of the reasons

source: printed in Shenzhen