3. Drum 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, resulting in unsteady operation 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.

4. Improper Overprinting Caused by Improper Guide Roller Adjustment

The non-parallel adjustment of the guide roller will affect the smoothness of the paper feeding, and the conveying speed of the two sides of the aluminum foil will not be synchronized, resulting in overprinting. Therefore, the preparation guide roller on the printing press should be adjusted less after leveling.

5. Unstable tension causes misregistration

During the gravure printing of aluminum foil caps, the diameter of the discharge roll gradually becomes smaller, and the diameter of the receiving roll becomes larger, so the printing tension is constantly changing. The change in tension directly affects the elongation of the aluminum foil. Therefore, if the front and rear tensions are changed frequently and irregularly during printing, overprinting is not allowed. In order to ensure the stability of the paper feeding, the tension control system should be installed separately for the unwinding part and the winding part of the aluminum foil cap gravure printing machine. However, in the actual production process, due to abnormal or improper control of the automatic tension control system, and the pressure in the printing production is unstable, the speed change is abnormal (such as unstable motor rotation speed), the aluminum foil roll is not installed or eccentric, and the aluminum foil contacts the guide roller. Changes in the coefficient of surface friction, etc., will cause the tension to change. Therefore, in addition to properly setting the take-up and unwinding tension according to the actual situation, and avoiding the tension being too large or too small, the tension should be kept as relatively constant as possible to avoid major changes.

6. Failure of Automatic Registration System Causes Misregistration

The automatic register system is a print-controlled command and control center that can issue command signals. Whether the command signal is correct or not and whether the order can be effectively executed are all related to the final result of printing registration. Any problem in any part of the automatic register system will directly affect the normal work of the entire system, resulting in overprint errors that cannot be corrected in time, resulting in inaccurate overprinting. Therefore, if the automatic register system fails, it is necessary to check each component of the system one by one to find out where the problem lies and to eliminate it. If necessary, please have professional maintenance personnel perform further inspections and repairs. The following points should be noted.

(1) Whether the position of the electric eye is appropriate, whether the light spot emitted falls on the mark line, whether there is sundries on the surface of the electric glasses, and whether the reflective plate is contaminated or not.

(2) Whether the electric light of the electric eye is normal or not, and whether the light bulb is burned out.

(3) Whether the Mark line meets the requirements, including the distance, size, and color contrast, etc. If the Mark line is poorly painted and the color is too light, it may cause difficulty in the scanning of the electric eye. The color of the Mark line should be slightly darker than the pattern color.

(4) Is the magnetic sensor working properly?

(5) Whether there is any abnormality in the overprint adjustment mechanism, whether the control motor is out of control, whether there is any other mechanical failure, etc.

(6) Whether there is a malfunction in the electronic control device.

7. Improper overprinting caused by incorrect arrangement of plate cylinders

Aluminum foil is a soft metal material. During the printing process, due to thermal expansion and tensile stress during the hot air tunnel, tensile deformation occurs, resulting in a gradual elongation of the aluminum foil material, which adversely affects overprinting. In order to make up for the overprint error, the plate cylinder diameter of each color group in the platemaking process must increase color by a certain coefficient in accordance with the color sequence. Generally, the diameter of the latter color plate cylinder is increased by 0.025 to 0.04 mm from the previous color. The increment coefficient of the plate cylinder diameter must meet the requirements of the printing process, otherwise it will make overprinting of some color groups inaccurate. At the same time, it is necessary to look at the color sequence when loading the plates. If the color sequence is mistaken, the order of the increments of the plate cylinders will be incorrect, which will also result in overprinting.

In addition, the arrangement of the color sequence at the time of plate making, the processing of the color registration, etc. will also have a certain influence on the printing overprint. For example: the color of the overprinting requirement should be arranged as much as possible on the adjacent color groups. And carry out the necessary trapping processing, for some of the smaller lines or text, it is best to use direct overprinting process. Otherwise it will make overprinting more difficult.

8. Causes of printing equipment cannot be overprinted

The mechanical manufacturing precision of the printing equipment itself and the technical level and stability of the automatic registration system used have a great influence on the overlay accuracy of the aluminum foil cap printing. In the actual production process, such a situation is often encountered: When a certain product is printed on a certain printing machine, it is difficult to register, but the printing of a printing press is very smooth and overprinting is also accurate. It can be seen that the reasons for the printing press itself cannot be ignored. In particular, domestically produced equipment has the problems of short life, wear, and aging. Therefore, it is necessary to strengthen the daily maintenance and maintenance of printing equipment, and to regularly check and overhaul it. Premature wear, aging, or failure of components can increase equipment life.

Of course, the reasons for the overprinting of caps on aluminum foil caps are not limited to the above-mentioned ones. There are other influencing factors, such as the viscosity and fluidity of the ink, the drying of the ink, and the amount of hot air in the drying tunnel. At the same time, many overprints are often the result of a combination of several factors. Therefore, for the failure of overprinting, it is necessary to analyze and eliminate them one by one from various aspects. We must establish ideas for preventing problems beforehand, develop good work habits, standardize process operations, pay attention to accumulating experience, and find and solve problems in a timely manner. Continuously improve the printing quality of foil caps.