Analysis and elimination of the pull gauge failure of offset printing machine
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A Heidelberg 102ZP two-color printing press often has a phenomenon that the pull tab is not in place when printing books. Although the paper pulling effect will be better after the pressure of the zipper spring is increased, there is still an error. This problem is not for all papers. If it is positive paper or four-open paper, the pull paper will be better, and the larger the paper size, the more accurate the pull gauge is. Printing two-color prints will have positive and negative errors, although this will not affect the quality of the product too much, but when printing four color pages, due to the pull gauge error will cause a lot of waste.
When printing four color pages at a time, considering the condition of the printed matter, the pull gauge used the outermost edge of the printed matter, and the error of the pull gauge was also more serious, and had to be stopped for inspection.
Fault check
First, increase the pressure of the spring, remove the upper part of the pull gauge, clean the bearing with gasoline and kerosene, add a little oil, and make the bearing flexible, but the effect of the test machine after installation is not significantly improved. Check the pull time of the pull gauge, no problem, adjust the eccentric shaft of the pull gauge bearing, from the smallest to the largest test machine, the results are not ideal. Finally, it is found that the gap between the pressure plate on both sides of the puller bearing and the magnetic plate in the groove on both sides of the lower plate of the bearing is too small, and the gap is gradually reduced from the middle to the outer transmission surface (in this case, the transmission surface pull gauge is used) ). Because the gap is too small, when the pull gauge bearing is pressed onto the paper to start pulling the paper, the pressure plate on both sides of the bearing is also pressed against the paper to generate resistance, preventing the pull gauge from pulling the paper and making the paper not in place. Since the gap between the pressure plate and the magnetic plate is gradually reduced from the middle to the transmission surface, the resistance is gradually increased from small to small, which is reflected that the paper is gradually inaccurate from small paper to large paper.
Failure analysis
The upper part of the pull gauge consists of a bearing and bearing bearing on both sides of the bearing plate, the lower part is a patterned pull plate under the bearing, fixed on a bottom plate sliding back and forth through the chute, and one with the transmission surface The drive links are connected and the drive rod provides the power to move back and forth. Due to the long use time, the bottom plate and the sliding groove rub against each other and wear and thin, the pulling plate fixed on the bottom plate also drops, the pull bearing and the pressing plate are pressed downward, and the magnetic plate in the pull tab groove is worn. It is small so that the gap between the pressure plate and the magnetic plate becomes small. Although it is worn at the same time, since one end of the transmission surface is connected to the transmission link and is subjected to the transmission force, the force receiving portion of the transmission surface is more worn than the intermediate end without the force receiving end, that is, the zipper plate is lowered by the intermediate transmission surface. Gradually increase, so the gap between the pressure plate and the magnetic plate is gradually reduced from large to large, reflecting that the resistance to the paper is increased from the middle to the transmission surface, and the pull gauge is gradually inaccurate.
Troubleshooting
If you replace the new one, it is more troublesome to disassemble and install, and the time is too late. Finally, it is decided to adopt a padding method to solve it. The specific method is as follows: firstly, a thin steel sheet with a thickness of 0.06 mm and the same length and width as the puller plate is added between the pull plate and the bottom plate; due to the serious wear of the transmission surface, a length of about 15 cm, a thickness of 0.15 mm, and a pull are separately added. Small steel sheets with the same width as the gauge plate cannot be completely padded at this time, otherwise the middle will be much higher. After the processing is completed, the test machine is printed, the pull gauge returns to normal, and the problem is solved, but it should be noted that the padding should not be too thick, otherwise the pull plate will be too high and the pull gauge will be inaccurate.
In addition, the same method can be used to repair the pull tab. If this phenomenon occurs on the four-color offset press in Heidelberg, it will not affect the four-color overprint, but it will affect the positive back error, but it can also be handled by this method.