Ink bar troubleshooting
We are a big printing company in Shenzhen China . We offer all book publications, hardcover book printing, papercover book printing, hardcover notebook, sprial book printing, saddle stiching book printing, booklet printing,packaging box, calendars, all kinds of PVC, product brochures, notes, Children's book, stickers, all kinds of special paper color printing products, game cardand so on.
For more information please visit
http://www.joyful-printing.com. ENG only
http://www.joyful-printing.net
http://www.joyful-printing.org
email: info@joyful-printing.net
The aging of the equipment has caused many printing failures to occur on the Heidelberg offset press, which has a higher precision. Especially after the replacement of imported parts by domestic parts, the fault phenomenon is particularly obvious. Serious ink breaks occurred when printing 880mm × 540mm prints on two offset presses from Heidelberg 102V (enabled in 1986) and 102F (enabled in 1992). The ink bars of each color group appeared at the mouth of the paper. At 540mm, there is a special bright mark on the surface of the impression cylinder that is different from the other surface at 540mm, and the ink frame on the paper is exactly the same length and width as the trace. When the fault was eliminated, the operator took many detours, but the problem was finally solved. The troubleshooting is now described below for reference by peers.
Fault phenomenon
The two multi-color offset presses of Heidelberg 102V and 102F have been printing 780mm × 540mm paper for many years. With the opening of the book, the paper has been printed to 880mm × 540mm. When the operator used Heidelberg 102F to complete the magenta and yellow plate overprinting, it was found that there was a ink bar about 80 mm from the paper tip. At the beginning, it was considered that there was a problem with the magenta group, and the ink roller and the ink roller were inspected and inked. The pressure between the roller and the printing plate, check the ink roller seat for stagnation and looseness, and replace the new blanket and pad with the technical parameters, re-test the device after the machine is at the highest speed, and the ink frame still exists. . The operator switched the magenta version to another color group and the ink frame still exists. Due to the tight delivery time, the operator had to switch to Heidelberg 102V for printing. Unexpectedly, the ink stick appeared on the same position as the paper. Therefore, the operator suspected that there was a problem with the film, so the film was changed to the direction of the test machine, and the ink bar was still in the same position, so that the ink bar was determined to be independent of the ink roller and the film.
Next, I started to check the mechanical aspect. When a piece of printed inked paper was placed in the front gauge and entered into the printing color group inspection, I accidentally found that the surface of the impression cylinder had a brighter mark on the other surface. Just in the same position as the ink stick on the paper, the operator went to check other color groups and found that there was such a bright mark in the same position of each color group. In the past, the two Heidelberg printing presses mostly printed 780mm × 540mm paper. The impression cylinder had a certain degree of wear at a distance of 540mm from the 叼, and it was judged as an “imprint roller wear bar” that could not be solved.
Troubleshooting
The two Heidelberg multi-color offset presses, 102V and 102F, have been in use for more than 10 years, and long-term three shifts and offset paper printing have increased wear and tear on equipment. If the ink bar is caused by the impression cylinder, it means that the two devices can only print the printing of 780×540mm or less, so the operator decides to confirm whether it is caused by the impression cylinder.
When visually and hand-measuring the surface of the embossing cylinder, the operator found that there were bright marks on the left and right sides of the 780 mm position of the 780 mm × 540 mm gauge, but when printing the 880 mm × 540 mm size print, there was a circumferential trace on the paper. . Therefore, the operator first presses the device and checks the roller with a fuse. As a result, the three rollers are not abnormal, and all meet the technical parameters, and the gap is 0.05 to 0.06 mm. Secondly, with the plate cylinder, the relative position of the pattern is changed, but the ink bar is still at 540mm. The operators who have used Heidelberg equipment know that the three-point county floating type used by the pressing mechanism has been adjusted at the center of the three rollers, and it cannot be moved casually, and the plate is also fixed. Pads, each time the plate is installed, it does not need to be replaced like a domestic offset press. Each time the plate is loaded, it does not need to be replaced like a domestic offset press, but this time the operator decided to break the technical parameters specified in the Heidelberg specification. The liner immediately attached to the printing plate was peeled off, the glue on the surface of the plate cylinder was washed away, the pressure gauge was placed at the “0” position, and the roller housing was pressed with a fuse having a diameter of 4 mm. Experimental results: the gap between the impression cylinder and the blanket cylinder is 3.2 mm, and the gap between the blanket cylinder and the plate cylinder is 3.65 mm. From the above data analysis, the usual blanket + pad thickness is 3.25mm, plus the thickness of the printing paper, the printing pressure is about 0.13mm, and the printing plate + pad thickness is 0.6mm, then the blanket cylinder and the plate cylinder The printing pressure between them is 0.2 mm, indicating that the printing pressure between the blanket cylinder and the plate cylinder is too large. Therefore, the operator reduced the plate + pad thickness to 0.5 mm test print, so that the printing pressure between the blanket cylinder and the plate cylinder was about 0.1 mm, and then the test was printed, and the failure disappeared. The plate liners and rubber liners of the two Heidelberg presses are now used according to the above data, and the so-called "imprint roller wear bars" of each color group are all eliminated.
Lessons Learned
The reason for the appearance of the circumferential 540mm ink bar is that for more than 10 years, most of the two offset printing presses printed the 780mm×540mm offset paper textbooks. Because of the rough surface of the paper, the printing pressure is higher than that of the surface smoothness paper ( For example, coated paper, etc.) should be too large, so the gap between the plate cylinder and the blanket cylinder is small when the pressure is combined. For a long time, the roller gears of each color group will be subject to different degrees of wear in the circumferential direction of the printing web at 540 mm. In the case of 880mm paper, the same printing pressure will increase the vibration of the gear at 540mm, so it is necessary to readjust the printing pressure.