Troubleshooting of angle swing of the hottest Heid

The author once participated in the relocation, installation and commissioning of a Heidelberg 102 four-color offset press, which has been in good operation for more than half a year since it was put into production. However, a batch of 157g/m2 large folio coated paper printing has been undertaken recently. The layout has a large area of four-color overprint background color, and is full of anti white text. After printing, the third unit of the machine has obvious angle throwing phenomenon, resulting in inaccurate overprint of anti white text

during the relocation of the equipment, the author personally overhauled the machine, especially carefully adjusted and renewed the teeth and tooth pads of the paper transfer and imprint cylinder, and it is estimated that there will be no problems. Therefore, it was first suspected that there was a problem with the printing pressure and drum lining, but at that time, the machine operator was very sure that the pressure adjustment and the plate cylinder and rubber drum lining were absolutely in line with the standard, and there was no problem. Therefore, we focused on the teeth of the paper transfer drum and the imprint drum, but after careful inspection and adjustment, the problem has not been significantly solved. At this time, we suspect that the ink viscosity of unit H 3 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 into the conventional color sequence of K, C, m and y, but the result is still not good, but the pollution is extremely serious

we carefully measured the deviation value of each drum, and found that the deviation value of the rubber drum and plate cylinder of the third unit was significantly higher than that of the other three units, which was believed to be due to the wear of the double row cylindrical roller bearings at both ends of the drum. So far, everyone believes that the cause of the fault has been found and the worn bearing should be replaced. However, for one thing, the cost of replacing the bearing is too large, and for another, the parking time is long, delaying production. Moreover, based on the author's experience, although excessive drum clearance sometimes leads to angle rejection, from the measured drum clearance, the angle rejection should not be so serious, and the drum bearings of the third color group cannot be worn out for no reason

we once again focused on the rubber drum lining to open up domestic and foreign markets, opened the rubber blanket for inspection, and 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. Heidelberg offset press uses a hard liner, and the rubber drum liner is 0.10mm more, which has a great impact. Later, the machine operator recalled that it may be that the operation was careless when changing the bag lining, and an additional lining paper was added. In this way, the two shift production and use of nearly half a year. In this way, it is not surprising that the roller bearings are seriously worn. Re lining, trial printing, angle rejection failure has significantly improved. Although there is still slight angle rejection due to bearing wear, after careful adjustment, it can basically meet the requirements of live parts, and the overprint of anti white words is also relatively accurate

we found several batches of prints printed by the machine within half a year, and found that the phenomenon of corner throwing had already appeared. When the lining was wrong, it appeared, but the requirements of live parts were not very strict at that time, and it was not very obvious from the live parts themselves, so it did not attract the attention and attention of machine operators and relevant management personnel

warning of this example of angle swing failure:

① the machine operator must have a high degree of heart and skilled operation skills. The adjustment of the equipment, especially the adjustment of the lining and printing pressure, must be carefully carried out after accurate calculation, and no carelessness is allowed. After adjustment, you must try to print, carefully check and analyze the printed sheets, check the adjustment results, and eliminate problems in time

② the workshop and other relevant management personnel should also be serious and responsible, be diligent in management and inspection, especially the sample signing personnel and quality inspectors should be careful and careful when signing samples and carrying out print quality inspection, and must not ignore some seemingly insignificant hidden troubles because the prints basically meet the requirements and customers' approval at that time. The long-term existence of hidden dangers will often lead to serious consequences and eventually cause great economic losses to enterprises

③ when troubleshooting, you should not blindly believe the situation reflected by the machine operator, so as not to be biased and mislead the problem. 1 nm is the change-over switch, which should be turned to the "load" position 1 billionth of a meter (10 ⑼ m), and take unnecessary detours