Mechanical troubleshooting for Beiren J2205 offset press
When a Taipei J2205 split single-sided two-color offset press printed a batch of 450g/m2 thick cardboard, and then printed a single-sided coated paper two-color drug label with a basis weight of 80g/m2, it appeared on the printed product. The second color imprint has a large range of vertical ghosting (from the print mouth to the ruled midline position), and the distance between the lower and the deep blots is 1.5 mm. In addition, there are also the drawbacks of irregular paper feeding in the two sides, which seriously affects the quality of the products and cannot be produced normally.
In response to the above situation, the author summarizes the causes of the problem as follows.
(1) In the process of printing 450g/m2 thick cardboard, the impression cylinder is working under high load for a long time, which causes the fatigue of some of the crepe small compression springs to fail, the force drop and the crepe paper are unstable. Causes a ghost.
(2) After the printing material is changed from thick cardboard to thin paper, the pressure adjustment, the lining measurement and the coating operation between the rollers are improper.
(3) The pressure is too large when printing thick cardboard. In continuous printing, when the working surface of the drum is exchanged with the neutral surface, a large impact vibration is generated, resulting in loose or damaged related parts, resulting in ghosting and uneven feeding on both sides. .
According to the above analysis, the author first carried out a comprehensive inspection of the impression cylinder gripper, and replaced some fatigue-failed small compression springs to ensure that the angles of the grippers were in place, the length of the flaps was consistent, and the force was consistent. Next, strictly follow the standard technical parameters of the machine, carefully correct the gap of each drum shell, recalculate, measure and install the lining to ensure the pressure between the rollers is normal. After the boot test, the ghosting phenomenon was alleviated, but it was not completely solved.
To this end, we inserted the sled rod into the drum casing to swing back and forth, and inspected the transmission mechanism of the second color group blanket cylinder and the plate cylinder, and found that the plate cylinder had a large longitudinal movable gap. Remove the front and rear (upper and lower) micro-adjustment plate-making mechanism support blocks one by one, remove the transmission plate N73-20507, and find the transmission between the small shaft N73-20504 and the gear holder N113-20521 that drives the plate cylinder to rotate. The matching clearance is large, so that the plate cylinder generates a large swing during the rotation.
The fixed plate cylinder gear and the gear seat on which the transmission shaft is mounted are removed. It is found that one of the two M6 hexagon socket screws of the fixed transmission shaft has been broken, the other one has been loosened, the displacement is large, and the transmission is small. The fit between the shaft and the gear seat is a clearance fit. In order to ensure the reliability and stability of the transmission mechanism, during the maintenance process, we measure the fixing hole of the drive small can on the gear base, and carry out spraying and grinding on the corresponding installation parts; the small shaft and the gear seat of the transmission The fit between the two is changed to tight fit; when two M6 screws are installed, anti-loose rubber is applied. After the installation and adjustment, the test machine is printed, the ghost image disappears completely, but the phenomenon of irregular paper feeding on both sides still exists.
In this regard, we believe that it is likely due to the impression cylinder being loose and causing longitudinal displacement during rotation. According to the assembly drawing of the impression cylinder and its related transmission mechanism, the transfer paper cam N73-20106 is removed, and the positioning pin and the fastening screw are found to be severely loosened. After the screwing, the various parts of the machine are reinstalled, and the printing is started, and the ghosting and the two sides are not The failure of regular paper feeding is completely eliminated.