Practice of reforming gravure printing machine for printing on paper
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The gravure printing machine is a gravure printing machine, which is generally used for color printing of plastic film. However, it has not been reported for paper printing. The paper can be used for packaging various medical products after the hot melt is printed on the paper. Therefore, the gravure printing machine is used. Gluing for paper products is an innovation, and it is a pioneering enterprise that uses original equipment to carry out technological innovation and develop new products. Through such technological innovations, companies have saved many of the cost of purchasing equipment and increased the utilization of existing equipment.
1 gravure printing control system
The system itself affects the distribution status of the glue has the following parts:
1.1 Rubber roller - wire roller - scraper - glue tank system.
This system determines the coating amount of the glue, and ensures that the glue is distributed on the surface of the carrier paper with a certain distribution density. The coating state of the glue is mainly determined by the system.
1.2 Design of the glue tank:
The design of the glue tank plays an important role in the printing process because the hot melt melts a process. Namely: heating - melting - aging (yellow, black appear). Therefore, in order to melt the hot melt better, it is necessary to make the glue tank have a certain heat capacity so that the glue tank is kept at a constant temperature for a long time, and the temperature in the glue tank is uniform. In view of this, the design of the tank wall is required. Thick, there should be vertical ribs in the middle of the groove to facilitate heat conduction. The width and depth of the glue groove should be determined according to the width of the printing paper and the diameter of the wire roller.
1.3 Blasting: The room temperature and ventilation conditions affect the hardening rate of the glue. The advantages of several groups of blasts in the printing press can be used to accelerate the curing of the glue with one or two groups of blasts.
1.4 Winding: At the beginning of winding, you must lay the bottom and stick the core.
2 raw materials
2.1 Hot Sol: Generally speaking, general hot melt can be used. The melting point of the hot melt produced by different manufacturers is different, and some differences are large. In order to ensure excellent coating state, it should be carefully identified before use.
2.2 Polyethylene wax: mainly used to control the firmness of bonding. The proportion of its ratio determines the quality of the packaging. Its selection must also ensure the quality, pay attention to the refractory crystal points, impurities and so on. In addition, it should consider its compatibility with the hot sol. If it is dissolved, it should be stirred with a thin layer of liquid. After mixing, it can be used. Otherwise, it will be used instead of glue on the paper. Produced.
2.3 Carrier paper: The choice of paper, one is based on the requirements of the user. The second is to pay attention to the tension of the paper. Otherwise, in the process of printing, break is a common phenomenon. Generally speaking, the tension of paper is far less than that of various plastic films; such as OPP, PET, NY, etc. Therefore, driving start should be steady, slow, and uniform. Rapid and sudden stop will cause paper to break and cause a lot of waste. On the other hand, the force of the paper roll on each guide roller should be consistent and the same size, otherwise it will be broken. Stopping, sometimes it will make the driving tester lose the confidence to try, and the paper storage time problem, generally speaking, should not exceed one year, otherwise the whiteness and toughness of the paper will be greatly affected, which must be paid attention to. It is best to buy it out.
3 process factors
3.1 Matching of mixed glue and screen roller: In order to make the offset on the paper suitable and the network cable clear, it is necessary to consider different sizing amount to adopt different wire roller. This is often negligent. Generally, the following working principles can be followed. The larger the amount of glue, the less the network cable used for the wire roller; the smaller the amount of glue, the more the wire of the wire roller used. General manufacturers can prepare three sets of wire rollers. That is, the 80-line set is used for the highest bonding fastness, and the coating amount is also the largest. The set of 100 to 120 lines is used for the bonding fastness, 130 to 150 lines, for ordinary bonding. Smaller products. In addition, the rubber roller and the wire roller must be parallel and have a certain pressure during operation. Otherwise, it will cause partial network cable loss, and there is not much glue transfer. Another is the diameter and width of the wire roller and rubber roller. It is also a factor to be considered. Try to find out the common specifications in use, and try not to affect the production. However, it is not enough to make rubber rollers and wire rollers, resulting in unnecessary waste.
3.2 Hardness adjustment of rubber roller: The rubber roller in the system provides a certain pressure to force the rubber to be extruded from the mesh and dispersed on the surface of the rubberized paper. The hardness of the rubber roller has a great influence on the dispersion of the rubber. There are two aspects worth noting. Firstly, the domestic rubber roller is generally not high in hardness, and the hardness of different manufacturers has a certain difference. The elasticity of the rubber roller will decrease with the extension of the use time. The softness and hardness of the rubber roller determine the amount of glue transfer. It is necessary to select a soft and hard rubber roller to make the glue mesh printed on the paper clear.
3.3 System cleaning: due to the characteristics of the hot melt: heating, melting, cooling and solidification. Therefore, pay attention to the cleaning of the printing system, various guide rollers, blast outlets, and both ends of the wire roller. In particular, sometimes the paper is broken in the glue tank and will bring a lot of glue into the system. If the cleaning is not clean, it will directly lead to The paper is crushed, vacated, and not glued.
3.4 Precautions for driving: Firstly, calculate the amount of glue before driving. If you need to preheat the rubber in advance, pour it into the tank in molten state. After one to two hours of constant temperature, melt the wax. The car can be driven when it is evenly distributed. Secondly, because the plate roller is not immersed in the glue tank, its temperature is low, and it cannot be driven. The plate roller should be immersed in the glue tank for 10 to 20 minutes, until the temperature of the wire roller and the glue are basically the same. When driving, the glue should be liquid. Then, when driving, the paper should be straightened so that the force direction is the same and the size is the same, so as to prevent the paper from being broken.
4 Workshop environment
Dust: The dust in the air of the workshop will adhere to the paper, destroying the firmness of the glue. Especially at the air supply port, the strong airflow will pinch the dust particles and sprinkle it on the paper glue, which will affect the product quality. Therefore, in addition to keeping the workshop clean, the filter at the air supply should be cleaned and replaced frequently.
Above we discussed the factors affecting the printing press and some methods to improve the printing effect. The normal production process is more complicated. When analyzing a certain quality problem, more comprehensive consideration is needed.