Damage to printing quality caused by bearing failure of the cylinder for rotary printing
Through the analysis of the failure of the cylinder for rotary printing bearing, it can be seen that to prevent the loss of the accuracy of the cylinder for rotary printing bearing, first select the type of lubricating oil used by the printing machine and replace it in time; secondly, keep the tension system of the printing machine in normal working condition, often maintain the tension system of the printing machine, make the tension output stable, so as to reduce the paper in the printing process The occurrence of winding drum with fracture. In addition, the selection of appropriate raw materials is also one of the effective ways to reduce the failure of printing press roller bearings.
The bearing accuracy of the cylinder for rotary printing and the printing accuracy of printing machine
Before the roller bearing of rotary printing breaks down, it will be reflected in operation and products indirectly or directly, but it has not attracted our attention. Sometimes, the method of increasing cylinder lining is adopted to solve the problems of printing pressure, uneven ink color, etc., but the printing machine will not be able to reproduce more than 80% of the dot level.
There are two kinds of faults in IKO roller bearing of the printing press: one is that the support frame is broken, the track surface of the inner ring and the outer ring is peeled off, which makes the ball movement not smooth and causes the mechanical lock. This kind of fault is obvious. Only after repair can the printing press operate normally. In fact, this kind of fault existed in another kind of fault before causing serious mechanical lock: the wear of the track surface of the support frame, inner ring and outer ring. This kind of fault is not obvious, which mainly affects the printing quality. It is also a fault that it is often not easy to attract people's attention to the maintenance of the printing machine because the printing machine can operate normally at this time. In the process of web printing, when the paper tape breaks and wraps around the drum, the force on the wrapped part will suddenly increase, resulting in lubrication failure, local bearing damage, increasing the clearance of the damaged part of the bearing, causing uneven pressure on the printing surface.
If the lubrication is in a half failure state for a long time, the bearing clearance will increase seriously due to the long-term wear of the track surface of the inner and outer ring of the bearing, which is usually manifested as insufficient printing pressure, uneven ink color of the printed matter, on-site roughening, etc., in serious cases, less than 30% of the dots of the printed matter will be lost, and more than 70% of the dots will be pasted. It is more common that after offset press is used for a long time, especially for the roller without running the roller pillow, its motion impact vibration is large, and the bearing is easy to produce wear, which makes the gap between the journal and the bearing increase and the sleeve is loose. When the roll is simply closed, its mouth vibrates due to the separation, resulting in sliding friction and forming a "bar". Especially when the load is not normal or the lubrication is not good, the wear of the shaft head and the shaft sleeve of the drum is intensified, and the "bar" is most likely to be generated near the mouth of the drum.
Secondly, the sundries or wear in the bearing, bearing seat and bearing lock of the water and ink roller can also cause obvious axial movement and radial run out of the water and ink roller in the movement, thus producing the "bar". Especially when the shaft sleeve or transmission gear of the ink roller is worn, the vibration produced by the meshing of the roller gear affects the normal water, ink, and transmission of the roller, leading to the appearance of the "bar".
It can be seen that the stability of the bearing is of great importance to the printing. Periodic maintenance is not needed. The authenticity of the bearing must be strictly controlled. If a fake bearing is damaged in the process of reprinting, the consequences will be incalculable!