Maintenance of the paper delivery tooth row of the

2022-08-17
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Roland four-color machine - maintenance of paper delivery teeth

Roland four-color sheet fed offset printing machines produced before the 1990s mostly have a structure of two groups, and the two groups are connected by multiple rows of paper delivery teeth. The teeth play an important role in accurate and stable paper transmission. Once damaged, the consequences are unimaginable

a 1985 Roland four-color machine, once the operator violated the operating procedures when filling the next color group with ink. Without pulling up the inking iron roller, he directly patted the ink on the running ink roller with an ink knife, causing the ink knife to roll into the ink roller, squeezing a heavy roller into the chain track, and bending two rows of paper delivery teeth. Therefore, it is extremely difficult to find the original paper delivery tooth row in China in order to operate more safely. Even if you contact the German manufacturer to find spare parts of the same model, the cost of spare parts alone (about 100000 yuan per row) is prohibitive. After inquiring about the printing factory that repaired the paper delivery tooth row, I learned that: first, the maintenance cost is high, about 150000 yuan for two rows; Second, the effect after maintenance is not ideal

with the idea of trying, the maintenance personnel began to repair carefully. Since the base point of the bottom of the tooth row and the processing surface at the tooth pad are not two parallel planes, and the degree of the angle between the planes is unknown, it can only be roughly calibrated after the tooth row (this machine has 10 paper transfer teeth row) trial printing. It was found that there were two inaccurate overprinting every eight sheets, one of which was facing away from the body, and the other was facing outward. Engel machinery (Shanghai) Co., Ltd. on both sides showed that the world's first infusion drip bucket one-step injection molding was inaccurate and the difference was more than 1mm. At first, the maintenance personnel tried to solve the problem by adjusting the size of the teeth row opening, changing the handover time with the embossing cylinder, and adjusting the teeth row with inaccurate overprinting with other teeth rows, but the phenomenon of inaccurate overprinting has not been improved at all

can the roller of the problem tooth row be adjusted to eliminate the fault with the widespread use of computer technology to make its joint position different from that of other tooth rows? We know that the precise connection between the tooth row and the embossing cylinder depends on the short fork on the chain gear shaft, one on the left and one on the right. The short fork forks the tooth row roller when the tooth row approaches the embossing cylinder and takes its teeth, making it separate from the inaccurate movement of the chain and enter the specified gear movement state, so that each row of tooth rows are in the same position and realize the connection with the embossing cylinder. Therefore, whether it is placed vertically or laterally, the roller diameter of a certain tooth row should be changed to make its distance from the impression cylinder different from other tooth rows, so as to achieve the purpose of adjusting the overprint error of a certain tooth row. Although there are still some problems in theory, in fact, the maintenance personnel used this method to eliminate the fault

it is worth noting that great care must be taken to change the diameter of the tooth row roller. If it exceeds the allowable range, it may cause serious consequences at any time. First, calculate the amount to be changed in advance. The specific calculation process: the included angle between the two forks of the fork is 44 °. According to the trigonometric function relationship, when the roller diameter increases by 0.5mm, the tooth row will move forward (compared with the position before the change) by about 1.2mm. First look at the error values of one group and two groups of overprint, and then decide the amount of increase or decrease in the diameter of the tooth row roller. Second, after replacing the roller, turn the gear. Pay attention to check the contact between the roller and the fork at any time. If the top is tight and the vehicle weight is at the same time, it indicates that the changed roller diameter is inappropriate. Remove the roller and readjust it until it is appropriate

although this is only a special case and not universal, I hope it can enlighten the self maintenance of imported equipment and help more printing plants solve practical production problems. (text: Deng Qi)

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