Heidelberg 102 four-color machine corner troubleshooting
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The relocation, installation and commissioning of a Heidelberg 102 four-color offset press, the machine has been in production for more than half a year and has been working well. However, a number of 157g/m2 large-scale offset paper printing has been accepted recently. The layout has a large-color four-color overprinted background and is covered with anti-white text. After the printing, the third unit of the machine has obvious “corner angle” phenomenon, which leads to partial overprinting of the reverse text.
When the equipment was relocated, the author personally overhauled the machine. In particular, the paper and the impression cylinder teeth and the dental pads were carefully adjusted and replaced. It is estimated that there will be no problems. Therefore, it was first suspected that there was a problem with the printing pressure and the drum lining, but at that time the machine operator was very sure that the pressure adjustment and the plate cylinder and the blanket cylinder lining were absolutely in compliance with the standard, and there was no problem.
Therefore, we focused our attention on the transfer roller and the impression cylinder, but after careful inspection and adjustment, the problem has not been solved. At this time, we suspected that the ink viscosity of the three units was improperly adjusted. At that time, the printing color sequence was: K, M, C, Y. Therefore, we changed the ink color sequence of the third unit and the second unit to become the regular color sequence of K, C, M, and Y, but the results still did not improve.
We carefully measured the "transfer value" of each roller and found that the transfer values of the rubber drum and the plate cylinder of the third unit were significantly larger than those of the other three units, and it was considered that the "double row cylindrical roller bearing" at both ends of the drum was worn. The reason. At this point, everyone thinks that the cause of the fault has been found, and it is necessary to replace the worn bearing. However, the cost of replacing the bearing is too great. Secondly, the parking time is long and the production is delayed. Moreover, the author has experience, although the roller shift value is too large, sometimes it will lead to the horn, but from the measured roller detachment value, The horns should not be so severe, and the roller bearings of the third color group are not likely to wear out without cause.
Once again, we focused our attention on the rubber roller lining and opened the blanket. It was found that the rubber drum lining of the third unit was 0.10mm more than the standard thickness, and the other three units fully met the requirements. The Heidelberg offset press uses a hard pad, and the rubber roller lining has an extra 0.10mm, which has a great influence. After the machine operator recalled, it may be that when the package is lining, the operation is sloppy, and a lining paper is added, so that the two-shift system is produced and used for nearly half a year. In this way, it is not surprising that the roller bearing wear is severe. Re-lined, trial printing, corner failure is obviously improved, although the bearing wear still has a slight corner phenomenon, but after careful adjustment, it can basically meet the requirements of the job, and the overprint of the reverse text is more accurate.
We found a few batches of printed parts printed in the machine for half a year, and found that the corner phenomenon has already appeared. When the package lining is wrong, it appears, but the requirements for the job are not very strict, from the point of view of the job itself. It is not very obvious, so it does not cause the attention and attention of the machine operators and relevant management personnel.
The warning of this corner failure:
1 machine operator must have a high degree of responsibility and skilled operation skills. The adjustment of the equipment, especially the adjustment of the lining and printing pressure, must be carefully calculated and carefully carried out, not allowed to be sloppy. After adjustment, you must try to print, and carefully check and analyze the printed sheets, check the adjustment results, and find out the problems in time.
2 The workshop and other relevant management personnel should also be conscientious and responsible, diligent in management and inspection, especially the signing personnel and quality inspectors should be serious and careful when signing and checking the quality of printed products, and must not be basically consistent with the printing at that time. Requirements, customer approval, neglected some seemingly insignificant faults. The long-term existence of hidden dangers often leads to serious consequences and ultimately causes greater economic losses to the enterprise.
3 When troubleshooting, you should not blindly believe the situation reflected by the operator of the machine, so as not to bias the bias, misunderstand the problem, and take unnecessary detours.