Analysis of the Eight Causes of Beer Foil Cap Standard Overprinting (I)

In the process of gravure printing beer foil caps, overprinting is not a very common fault. In particular, with the increasingly fierce market competition, products with more than five colors have been increasing, customers have higher and higher requirements for print quality, and printing overprint problems have become more prominent. At present, a considerable part of the printing loss is caused by overprinting. Therefore, if we want to improve the printing quality of beer foil caps and reduce the production cost, we should effectively control and reduce waste caused by overprinting.

The thickness of aluminum foil used in beer foil caps is only 0.0115mm. The main ingredient is pure aluminum and its texture is very soft. In the gravure printing process, due to the long printing route, due to tensile deformation, thermal expansion and contraction, and other factors, aluminum foils will continuously produce overprinting errors. If these errors are not corrected in time, the accumulation will exceed a certain limit. Will cause the product to be scrapped.

The reason for overprinting errors is constantly changing. Therefore, to improve overprinting accuracy, these errors must be continuously monitored and corrected in a timely manner. For the low-speed aluminum foil cap gravure press, the overprinting error can be corrected by visual inspection and manual adjustment. The correcting mode is divided into two types according to the different models: one is through the compensation roller adjustment, and the other is through the plate roller. Phase adjustment. The high-speed aluminum foil cap gravure printing machine mostly uses the method of phase adjustment of the printing roller.

Manually controlled overprinting is not suitable for high speed and high quality due to the disadvantages such as high labor intensity and large human error. Therefore, modern high-speed aluminum foil cap marking machines have generally used automatic registering systems to print overprints of various color groups. Tracking, detection and correction are all done automatically by the system. Automatic register system is mainly composed of electronic control device, electric eye (photoelectric scanner), pulse generator, overprint adjustment mechanism, oscilloscope (monitor), etc. The basic principle is through the electric eye (photoelectric scanner) for each color group The Mark line (register mark detection mark) is tracked and detected in real time. After the electronic control device analyzes and contrasts the signal, the overprint error is discovered in time, and the corresponding control signal is sent out. The overprint adjustment mechanism completes the overprint error correction.

There are various reasons for inaccurate stamping of gravure foil caps. In order to effectively reduce the occurrence of misprints, it is necessary to understand and analyze these causes, and take corresponding measures according to the actual situation.

There are several reasons why the overprinting of aluminum foil caps is not allowed.

1. Foil wrinkles cause misregistration

Aluminum foil is very soft, it is easy to wrinkle during the printing process, resulting in overprinting is not allowed. The causes of wrinkles in the aluminum foil and the corresponding countermeasures are as follows.

(1) The printing pressure is not uniform and the embossing roller is high on one side and low on one side. At this time, the embossing roller should be adjusted so that the pressure on both sides remains uniform.
(2) The embossing roller surface is uneven or ink is adhered on both sides. The solution is: 1 Remove the uneven surface of the rubber roller, replace the smooth, flexible, flexible rubber roller, uneven rubber roller can be re-processing; 2 the adhesive on both sides of the roller to clean the ink.
(3) The roller is uneven or adhered with ink. Aluminum foil printing requires high requirements for each guide roller. A slight deviation in parallelism can cause wrinkles during printing. Therefore, it is necessary to adjust the guide roller. In addition, the ink easily adheres to the guide roller, which causes the aluminum foil to move unevenly and wrinkles. Therefore, the guide roller must be inspected and cleaned regularly to ensure the smooth printing.
(4) During the printing process, the aluminum foil unwinding tension is too large to cause bouncing, or the unwinding tension is too small to cause the uneven force of the retractable roll to cause wrinkles. The solution is to adjust the tension of the retracting roll so that the tension is consistent and reasonable.
(5) Problems with aluminum foil itself, such as inconsistent thickness on both sides, or wrinkles on its own. In this regard, the aluminum foil material needs to be replaced.
(6) The fluidity and drying speed of the ink and the hot air temperature of the oven will also have a certain influence on the aluminum foil. Therefore, when aluminum foil wrinkles occur during the printing process, these factors must also be checked.

2. Misalignment of imprinting roller pressure causes misregistration

During the printing process, the pressure at the two ends of the imprint rubber roller should be kept the same. If the air pressure is insufficient (such as the air system leak) or the pressure adjustment at both ends is unbalanced, the imprint rubber roller will jump up and down during the printing process. The solution is: to check the air system, such as air leakage, replace the air leakage pneumatic components or the imprinting rubber roller so that the imprinting roller and the printing plate are completely in line with each other during printing. The pressure is kept constant and consistent.

3. Roller loosening causes misregistration

Aluminium foil cap marking gravure printing machine uses a shaftless cylinder. The above version is not tight. In the high speed printing process, the printing plate cylinder will loosen, which will cause the operation to be unstable or beating, which will result in overprinting. In addition, the conical head or taper hole has accumulated ink or foreign matter, which will also affect the plate printing effect and the smoothness of the plate cylinder operation. Therefore, the cone head and cone hole must be cleaned when the plate is on, ensuring that the platen cylinder is tight.

(to be continued)