A case of ghosting troubleshooting during printing

I company introduced a Taiwan and France Goss Universal 45-type rotary printing machine in 2005, with two towers and a folding machine. This year it has had a tough problem that has been bothering us for a long time. After continuous analysis, exploration, troubleshooting and testing, I finally found the cause of the failure and successfully solved the failure. Below, the author will share the specific exclusion process for everyone.

Fault phenomenon

When the newspaper was printed, it was found that there was a ghost image having a width of about 10 to 15 cm at the axial fixed position of the newspaper. The ghost image did not appear when it was first turned on, and it began to appear when printing about 60,000 copies of newspapers, and as the printing time went on, the phenomenon of ghosting became more and more obvious.

Troubleshooting process

First of all, it is suspected that there are problems with bearings, gears and other active and passive transmission mechanisms. After investigation, it was found that these devices have no obvious damage, and the errors and gaps are within a reasonable range.

Then, it was suspected that there was a problem with the blanket or blanket cylinder liner. Because the blanket or blanket cylinder liner can not restore the flatness in time due to long-term use or poor quality, and the temperature of the blanket will continue to increase during the printing process, these may cause ghosting. . So, we replaced the new blanket, the new blanket cylinder liner, but the fault still exists after the boot.

Later, it was considered that the rubber roller may cause a jump at the notch of the plate groove due to the unsatisfactory rotation of the bearing or the insufficient expansion and contraction force of the cylinder, thereby causing the rubber roller to slightly slide on the printing plate, thereby causing a ghost phenomenon. Therefore, the bearings and cylinders of each of the rubber rollers were inspected one by one, but after the boot, it was found that the fault still existed.

Finally, when the machine was being serviced once, it was accidentally found that the lock nut at both ends of the roller-clamping link was loose. To prevent printing pressure instability, we checked the roller gap

The inspection method is as follows: a cardboard paper with a quantity of 180g/m2 is placed between the blanket cylinder and the plate cylinder, and after pressing, the flashlight is illuminated from the side of the drum to the middle of the two roller cones, and the transmission is viewed from the other side of the drum. Whether the bolster clearance on the side and the operation side is the same. During the inspection, we found that there was a section of the light that was transmitted through the area when the machine was jogged.

Therefore, we suspect that it is possible that the roller gap is uneven due to the wear of the roller, which makes the drum unstable during operation, resulting in ghosting. Because the cost of replacing the roller is too high, we have reduced the overall roller gap of the unit to a small extent. After the power is turned on, the ghosting fault is solved.