Offset printing machine tearing paper failure
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In the production process of various printing plants, the phenomenon of handing over tearing paper is a common occurrence. The appearance of such a failure not only brings some trouble to the operator, but also affects the quality of the product. The tearing paper failure is sometimes simpler, and it will be solved soon after adjustment, and sometimes it is more complicated and can be solved by groping. In order to make the operator take less detours when troubleshooting the tearing paper, our practice is described below for reference.
A J2108 offset printing machine does not tear paper when printing paper of 100g/m2 or more, and paper tearing occurs when printing paper of 80g/m2 or less; tearing paper at high speed and not tearing paper at low speed. After this situation appeared, it added a lot of trouble to the maintenance staff. Before the advent, due to the accuracy of the machine, it is mainly used for some fine products such as printed cover, color photos and maps. As the age of use increases, the accuracy decreases, and this Yintian machine is changed to print the text of the book. In the printing process, the phenomenon of tearing paper appeared. At the beginning, it was considered that after using this machine for several years, the dental pad was severely worn, the height was unbalanced, the strength of the crepe paper was inconsistent, and the size of the open teeth was uneven. Therefore, we have replaced and adjusted the accessories, but the fault has not been solved after the test machine. It seems that the problem is not on the paper, will it be related to the handover time?
After observing at low speed, the paper runs straight, and the time before reaching the front is appropriate. The arm of the swing arm is the same, the amount of paper is 7mm, and the strength of the paper is not small. The swing arm and the impression tooth are smoothly connected, the time is right, and there is no tearing paper. There is no abnormality in the intersection of the impression tooth and the delivery tooth. After repeatedly moving the paper and jogging the machine, it was found that there was a paper receiving tooth at the time of handover, and the sound of the hanging paper could be heard, and several small tears appeared at the mouth. According to this situation, we carried out an analysis and thought that there was an error in the delivery time between the delivery tray and the imprinted gums. The delivery teeth were a little early, and the two teeth were connected to hold the paper synchronously for a short time. When the teeth have not been opened, the delivery paper has moved forward with the paper, and the paper is robbed, so the paper will be torn. According to the transfer principle of the printing machine, the paper needs to be accurate and stable when it is handed over, that is to say, the two rows of teeth have a constant speed after the paper is jammed, about 2°~3°, and the embossed crepe paper is opened. The paper can only take the paper out, the time can not be too late or not late, otherwise it is not the tearing paper as mentioned above, that is, the handover is unstable, there are some inconsistencies in the paper, the paper is inconsistent or the paper is dropped.
Why does thick paper not tear thin paper torn, high speed tear paper does not tear paper at low speed? Because thick paper is more than wood pulp, it has a large tensile force, good toughness, and is not easy to tear paper. Compared with thin paper, the quality of paper is not as good as thick paper and wood pulp, and the toughness and tension are poor. It is brittle and easy to be torn. The high-speed tearing of the printing machine does not tear the paper at low speed, mainly when the high-speed operation, the vibration makes the running smooth, the handover time is short and fast, and there is a great impact force and inertia. When the handover is slightly uncomfortable, the paper will be torn; It runs smoothly at low speed, has no inertia and impact force, and the handover time is slow and long, so it is not easy to tear.
According to the above analysis, the problem is determined on the opening plate of the delivery roller. The opening plate should be adjusted to delay the opening time of the delivery tray, but the open plate has been adjusted to the limit. We will remove the open plate, according to the direction of adjustment, use the round file to increase the hole length by 6mm, increase the adjustment margin, and the modified open plate is installed on the machine. good.