It is not uncommon for various printing houses to take over and tear paper during the production process. The occurrence of this kind of trouble not only brings some trouble to the operator, but also affects the quality of the product. Paper tearing faults are sometimes simple, and will be resolved soon after adjustment, and sometimes they are more complex, which can be solved by fumbling. In order to allow the operator to avoid detours when troubleshooting the tearing paper, we will introduce our approach as follows for reference.
Our factory has a J2108 offset printing machine that does not tear paper when printing paper of more than 100g / m2, and tears when printing paper of less than 80g / m2; tearing paper at high speed and not at low speed. After this situation appeared, it added a lot of trouble to maintenance personnel. Before it appeared, it was mainly used to print cover, color photos, maps and other fine products because of its better precision. As the service life increases, the accuracy decreases, and this printing machine is changed to print the text of books and periodicals. In the printing process, the phenomenon of tearing paper appeared. At the beginning, the inspection found that after several years of use of this machine, the dental pads were worn seriously, the height was uneven, the gripping force was inconsistent, and the size of the teeth was uneven. Therefore, we have carried out the replacement and adjustment of accessories, but after the test machine, the failure has not been resolved. It seems that the problem is not on the paper teeth, is it related to the handover time?
Observed by the low-speed operation, the paper runs straight, and the time before the arrival is appropriate. The swing arm gripper teeth open uniformly, the gripper paper amount is 7mm, and the gripper paper strength is not small. Swing arm teeth and embossed teeth hand over smoothly, at the right time, without tearing paper. There is no abnormality in the connection between the embossed teeth and the paper-receiving teeth. After repeatedly putting the paper and jogging the machine, it was found that there was a pick-up tooth lined up during the handover, and the sound of hanging paper could be heard, and a few small tears appeared at the mouth. Based on this situation, we conducted an analysis and concluded that there is an error in the delivery time between the delivery tooth row and the impression tooth. The delivery tooth row closes the tooth a little early. The time for the two teeth to transfer and hold the paper to run synchronously is short, and the impression tooth When the teeth have not been opened yet, the paper-receiving row has moved forward holding the paper, and the paper snatch appears, so it will tear the paper. According to the handover principle of the printing press, the paper needs to be accurate and stable during the handover. That is to say, after the two rows of teeth hold the paper, there is a distance of constant speed operation, which is about 2 ° ~ 3 °. In order to pick up the paper, you can take the paper away. The time can't be early or late. Otherwise, it is not like tearing the paper as mentioned above, or the handover is unstable, and there is some inconsistency or a paper drop in the air.
Why doesn't the thick paper tear the thin paper and the high speed tear the paper at the low speed? Because thick paper has more pulp than wood, it bears a high tensile force, good toughness, and is not easy to tear. Compared with thin paper, the quality of paper is not as good as thick paper, wood pulp, toughness and tensile strength are poor, brittleness is greater, and it is easy to be torn. The high-speed tearing of the printing press and the low speed of the paper are not tearing, mainly because the vibration makes the operation smooth during high-speed operation, the transfer time is short and fast, and has a large impact force and inertia. When the transfer is slightly uncomfortable, it will tear the paper; and The low-speed operation is stable, without inertia and impact, and the transfer time is slow and long, so it is not easy to tear.
According to the above analysis, it is determined that the problem is on the opening plate of the take-up roller. The opening plate should be adjusted to postpone the opening time of the delivery line, but the opening plate has been adjusted upward to the limit. We took off the open tooth plate and used a round file to lengthen the hole file by 6mm according to the direction of adjustment, which increased the adjustment margin. The modified open tooth plate was installed on the machine. good.
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