Rotary Printing Breaking Causes and Prevention

For rotary presses, stopping the paper during the printing process or causing equipment failure is a very thorny issue. According to several years of work experience, the author summarizes and analyzes the causes and preventive measures, and discusses with peers here.

1, the harm of rotary printing broken paper

Most rotary printing products are large-volume print products, and the printing speed is fast. The paper undergoes a relatively large tension in the printing process. After the printing, it is also folded. The paper paper must maintain a certain paper surface tension during the entire paper feeding process. Adapt to the needs of rotary printing. There are many factors that affect the paper surface tension in the printing process. The faster the printing speed is, the greater the tension is, and the higher the probability of paper breakage is. Whether it is manual paper-cutting or automatic paper-feeding, it takes 10 to 20 minutes for the paper to be re-threaded and then printed on the printer. Not only increase the labor intensity, waste of paper, affecting the printing speed and quality stability, if broken due to equipment failure, damage to mechanical components, rolling bad blankets, but also need to stop maintenance, so that the timeliness of newspaper printing requirements is difficult to guarantee . Therefore, we must pay full attention to the issue of paper breaks and try to avoid the occurrence of paper breaks.

2. Analysis of causes of web breaks caused by rotary printing

(1) Web quality problems and improper handling

When the printing paper tape is normal, the entire paper path should be relatively stable, the paper surface tension distribution is relatively uniform, and the small fluctuation of the paper can be controlled by the tension control system to control the paper force within a certain range. If the quality of the web does not meet the requirements, such as inconsistent tightness, uneven thickness of the paper or improper transport causes the web to be deformed and the paper core shifts. During the printing process, due to the inconsistent radial size of the web, the web is at a high speed. When the dancer roll is difficult to adjust the tension to the normal printing range, severe breaks may occur during printing. Therefore, when selecting a web supplier, we must choose a factory with high reputation and stable quality. Although the price of a small factory is cheap, if it causes breaks, it will not be worth it.

(2) The startup speed is not stable

When the printer is turned on, the printing speed is fluctuating, which inevitably causes the force of the paper strip to suddenly increase or decrease. As a result, the adjustment function of the tension balance system is greatly weakened, and paper breakage occurs easily. Therefore, when starting up, you should accelerate slowly and quickly.

(3) excessive dust accumulation in the paper guide roller

The ink scale and dust accumulation cause the radial size of the paper guide roller to increase. If the set tension does not change, the actual tension of the paper tape will increase, and the paper surface tension will be unevenly distributed, which is very likely to cause paper breaks. Periodically clean the paper guide roller during routine maintenance.

(4) Improper operation

In the printing process, there are many factors that affect the strength of the paper. For example, the adhesion of the blanket to the paper during printing, the peeling force of the ink on the paper, and the wetting of the dampening solution on the paper will cause the surface strength of the paper to decrease to varying degrees. When the influencing factors exceed the adjustment range of the tension control system, Paper breaks easily. For example, when the printing plate is stopped and replaced, the condensed water droplets on the machine baffle are not cleaned, and excessive water accumulation will flow to the plate cylinder. When the printing is started, the water droplets are transferred from the roller to the paper. The excessive amount of water absorbed by the paper causes the mechanical strength of the paper to be greatly reduced, which can easily cause breaks.

(5) aging blanket

Due to the erosion of the ink fountain solution and paper residues, the surface of the blanket is prone to problems such as aging, swelling, and convex cracks, and the ink transfer performance of the blanket is reduced. In particular, cracks appear on the edge of the blanket, and the pressure of the blanket is applied when the paper is imprinted, which results in a significant drop in the tension of the paper, which can easily cause breaks. The blanket should be replaced on a regular basis according to the print situation.

(6) Influence of Ambient Temperature and Ink Viscosity

The environmental temperature of the workshop or other factors may increase the viscosity of the ink, increase the adhesion of the paper to the ink and the blanket, and increase the peeling tension of the paper. The faster the printing speed, the greater the peel force will be when the tension is exceeded. When the system adjustment range is suppressed, it is extremely easy to cause paper breaks.

(7) Mechanical failure

Some mechanical parts in the printing have failed. For example, a break in the tension control mechanism, a break in the web break mechanism, a paper break in the paper breaker, and the like may result in a web break.