Troubleshooting and phenomena of the hottest ink b

2022-07-30
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Ink bar troubleshooting and phenomenon

the aging of equipment makes many printing faults also appear on Heidelberg offset printing machines with high accuracy, especially after domestic accessories replace imported accessories. 880mm is printed by two offset presses, Heidelberg 102v (enabled in 1986) and 102f (enabled in 1992) × There is a serious ink bar failure when printing 540mm size. The ink bar of each color group appears 540mm from the mouth of the paper, and there is a particularly bright mark on the surface of the imprinting cylinder 540mm from the mouth of the paper, which is different from other surfaces in the national new material industry "1025" development plan issued by China, and the ink frame on the paper is the same as the length and width of this mark. The operator took many detours in troubleshooting this fault, but the problem was finally solved. Now the troubleshooting process is described as follows for colleagues' reference

fault phenomenon

Heidelberg 102v and 102f multi-color offset printing machines have been printing 780mm for many years × With the internationalization of the size of books and periodicals, the 540mm paper is printed with 880mm × 540mm size paper. When the operator used Heidelberg 102f to complete the overprinting of magenta and yellow plates, he found that there was an ink bar about 80mm away from the trailing tip of the paper. At first, he thought that there was a problem with the magenta group, so he checked the pressure between the ink roller and the inking roller, between the inking roller and the printing plate, checked that the ink roller seat was worn and loose, and replaced the new blanket and liner according to the requirements of technical parameters, and tried to print again after the equipment was in the best state at high speed, The ink box still exists. The operator changed the magenta version to another color group for printing, and the ink frame still exists. Due to the tight delivery time, the operators had to change to Heidelberg 102v for printing. Unexpectedly, the ink bar or the paper appeared at the same position. Therefore, the operator suspected that there was a problem with the film, so he switched the film to another direction for printing and testing, and the ink bar was still in the same position, so it was determined that the ink bar had nothing to do with the ink roller and the film

next, check the machinery. When a printed paper with ink bars was placed on the front gauge and jogged into the printing color deck for inspection, it was accidentally found that there was a bright mark on the surface of the embossing cylinder, which was just in the same position with the ink bars on the paper. The operator went to check other color decks and found that there was such a bright mark at the same position of each color deck. In the past, most of the two Heidelberg printing machines printed 780mm × For 540mm paper, the embossing cylinder is worn to a certain extent at 540mm away from its mouth, which is determined to be an "embossing cylinder wear bar" that cannot be solved

troubleshooting

102v and 102f Heidelberg multi-color offset printing machines have been used for more than 10 years, and the long-term three shift operation and offset paper printing have aggravated the wear of the equipment. If the ink bar is caused by the impression cylinder, it means that these two devices can only print 780 × For prints with specifications below 540mm, the operator decided to confirm again whether it was caused by the embossing cylinder

during visual and manual inspection of the impression cylinder surface, the operator found that × There are also bright marks on the left and right edges of 780mm position of 540mm specification, but 880mm is printed × There are circumferential marks on the paper when printing 540mm. Therefore, the operator first closed the equipment and checked the roller pillow with a fuse. As a result, no abnormality was found in the three rollers, and they all met the requirements of technical parameters, with a gap of 0.05~0.06mm. Secondly, with the help of the printing plate cylinder, the relative position of the pattern is changed, but the ink bar is still at 540mm. The operators who have used Heidelberg equipment know that the three-point County floating type is used in the pressing mechanism. Before leaving the factory, the center distance between the three rollers has been adjusted to normalize the domestic machinery price, and can not be moved casually. In addition, the printing plate is also pasted with a fixed pad. It is not necessary to replace the pad every time when installing the plate, and it is not necessary to replace the pad every time when installing the plate, But this time the operators decided to break the technical parameters specified in the Heidelberg instructions. Peel off the liner clinging to the printing plate, wash off the glue on the surface of the printing plate cylinder, place the pressure gauge at "0", and use a fuse with a diameter of 4mm to press the cylinder shell. Experimental results: the clearance between impression cylinder and rubber cylinder is 3.2mm, and the clearance between rubber cylinder and plate cylinder is 3.65mm. According to the above data analysis, normally the thickness of blanket + pad is 3.25mm, plus the thickness of printing paper, the printing pressure is about 0.13MM, which is ideal, while the thickness of printing plate + pad is 0.6mm, so the printing pressure between the rubber cylinder and the printing plate cylinder is 0.2mm, indicating that the printing pressure between the rubber cylinder and the printing plate cylinder is too large. Therefore, the operator reduces the thickness of the printing plate + liner to 0.5mm. The use area of polyurethane material will be 1%~1.5% more than that of other thermal insulation materials for trial printing, so that the printing pressure between the rubber cylinder and the printing plate cylinder is about 0.1mm. After trial printing, the fault disappears. At present, the plate liners and rubber liners of the two Heidelberg presses are used according to the above data, and the so-called "embossing cylinder wear bars" of the color groups of the impact testing machines are all eliminated

summary of experience

the reason for the appearance of 540mm ink bars in the circumferential direction is that over the past 10 years, most of these two offset presses have printed 780mm ink bars × For offset paper textbooks of 540mm specification, due to the rough surface of the paper, the printing pressure used is larger than that of the paper (such as coated paper) with high surface smoothness. Therefore, the gap between the printing plate cylinder and the rubber cylinder is small when pressing. For a long time, the roller gears of various color groups will be worn to varying degrees at 540mm in the circumferential direction of the printed page. When printing 880mm specification paper, The same printing pressure will increase the gear vibration at 540mm, so it is necessary to readjust the printing pressure

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