Production of the hottest metal anilox roll 0

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In all modern printing processes, flexographic printing, which was neglected in the past, has shown great development potential in the range of narrow width and wide width printing. The entire supply industry has been successful through continuous improvement of methods, and through mutual cooperation to form a more acceptable way in terms of "flexo standardization", to achieve high and reproducible printing quality. Therefore, the printing press, embossing rollers, inks, plates, materials and all subsequent processes must be integrated at a high level, such as plate making, printing technology and quality control

this article provides some background information about the flexo roller. In flexo, the function of metal embossing rollers is to transfer ink, which is why they are so important in the printing quality control chain

if you have enough technical knowledge and practical experience, you will have more choices when purchasing. In the past, different manufacturers of corrugated metal rollers tried to recommend their products, but there was no set of standard specifications. For users, they would feel a little confused when purchasing. The main purpose of this article is to eliminate doubts on this issue through the main production process of metal corrugated rollers

important standards

the three most important factors in the production process of corrugated metal rollers are:

* material selection and structure

* ceramic coating or plasma treatment

* laser etching of inking holes

material selection and structure

the flexographic printing industry continues to face various needs with great differences and rapid changes, including short version printing, Therefore, attention must be focused on reducing the "non production time" and preparation time in the replacement of live parts. This includes the replacement of materials, plates, inks, and embossing rollers. According to the combination of printing units and the structure of printing machine, there may be some difficulties in selecting printing units more or less. Moreover, only a few narrow web printing machines are equipped with integrated lifting devices, while the situation is quite different in wide web rotary printing machines. Therefore, in narrow width rotary printing, the printer must lift the metal stripe roller to install it

the weight problem is not obvious for most of the narrow width printing with metal striated roller with smaller diameter. However, for solid stainless steel roller, the treatment process is quite strict. In general, the metal roll is not properly protected. If the ceramic coating at the end of the roller breaks, it is a typical example: it is difficult for the roller to move, but there are not enough protective measures

all advanced manufacturers of corrugated metal rollers provide hollow and light rollers. Aluminum alloy and stainless steel are commonly used in roll core production. The main cost lies in the service life material. The journal is made of stainless steel. What are the advantages and disadvantages of these materials? Aluminum is very light and easy to form because of its low hardness. In order to ensure its sufficient durability and stability, it is required to minimize its size, especially for the thickness of the roll core. An aluminum roll core and a stainless steel journal are a mixture of two materials with different expansion/contraction characteristics. Usually, the two materials should be bonded together very carefully to ensure that the rollers run concentric

stainless steel core is thinner than aluminum core. However, in order to ensure the internal balance of the stainless steel roll core, the internal and external parts of the stainless steel drum to be assembled are generally processed at the same time to achieve the required diameter. This precise process can ensure regular wall thickness and concentric operation of the rollers. The weight is reduced by thin-walled method. However, at least, the stainless steel journal is an important part of the weight of the roller beyond the core material. The weight of the precise and complex roller journal can be reduced by drilling. The journal with the same material as the roll wall is combined with each other by heating and matching to form a very accurate and permanent connection, which will not cause problems even at high temperature, while the adhesive connection is easy to cause problems at high temperature. In order to prevent ink or solvent from penetrating into the ceramic coating, it must be protected with chromium nickel coating. When treated with a highly corrosive solvent with a very low pH value, the entire roller must be coated to prevent the substrate material from being eroded. Usually, erosion occurs at the crack of the ceramic coating and stops at the surface of the drum. The "sandblasting" of the roller surface is the most important operation before coating. The air contains very regular particles, which are sprayed onto the roller surface with special equipment under high pressure. After correct execution, the dirt on the surface of the roller to be coated will be removed; Because oxides will affect the adhesion of ceramic coatings, they are also removed; In this way, a very fine surface is formed, which provides good adhesion characteristics for the ceramic coating

to achieve these goals, the "sand blasting process" must meet the conditions in the following main aspects:

the sand blasting equipment must be adjusted to be accurately parallel to the axis of the roller

the sand blasting device must be constantly updated to prevent dirt and ensure stable operation

roughness measurement and visual control to detect the minimum irregularity of the surface

the maximum time interval between sand blasting and coating must be determined according to the material used. This time must be as short as possible to prevent reoxidation of the surface

the oxidation rate of aluminum alloy is much faster than that of stainless steel, so the treatment process is also quite difficult. Nickel or high-grade stainless steel coating is much better. The next step after the ceramic coating "sandblasting" is the ceramic coating of the roller, which is very important for the quality of the metallic roll in the future

plasma is a well-known and widely used mixture of ionized gases. Chromium oxide is added to dissolve and accelerate its mixing with the rotating drum surface. The spraying equipment moves along the length of the roller until the required coating thickness is obtained. It must be noted that the coated roller cannot be cooled too fast to a certain extent, otherwise the adhesion of the coating will be reduced, and the homogeneity of the final coating will be greatly affected. After the roller cools, a single coating can be seen. High temperature has no effect on stainless steel pipes. This is completely different from aluminum. Usually, the temperature of the material is not constant. And the expansion rate of the material when it cools will lead to shrinkage problems. The quality of the plasma treatment process itself determines the final shape (porosity, hardness, structure) of a complete coating

the following two factors need to be considered:

* kinetic energy of ceramic particles impacting the roller

* thermal energy of ceramic particles

the computer control of the workstation designed by simec can complete the whole coating process, and can electronically measure, record and balance the flow speed of gas, plasma itself and energy supply. Unlike the previous plasma system, this precise production process ensures a stable heat supply

what needs special attention is ceramic powder. In the standard chromium oxide powder, the particle size range is microns. Even if other parameters remain unchanged, such a large difference can lead to great irregularity of the coating. For example, when small particles (5 microns) have evaporated, large particles (50 microns) are only partially melted. Usually, a thin coating will be more accurate and uniform. Large differences in particle size can and can lead to inaccuracies in laser etching

taking all these factors into account, simec system accurately detects chromium oxide powder under experimental conditions to ensure the necessary quality level and chemical needs. The test process is synchronized with the production process, and the results are printed out to serve the production. It has been proved that chromium oxide is the best surface material for laser etching, which has been replaced by numerical control equipment and PC software. Plasma coated chromium oxide is very durable because of its strong hardness and high density. If the treatment process of ceramic coating is very meticulous, the coating will be very hard and can hardly be damaged. These features form a high-quality surface with an estimated average growth rate of about 10% in "1025", so that the laser etching process can be carried out accurately to produce the required holes

laser etching with CO2 and YAG

generally, the laser etching unit is controlled by a computer, and its stored data can be recovered at any time to ensure a high degree of reproduction performance. The intensity of the laser beam is determined by the depth of etching. And focus on the surface of the roller through specific optical equipment. Diameter D, focal length f and wavelength of radiation capacity λ Determines the minimum point size s generated by the laser. The smallest point size is very important for the number of high lines and subsequent better holes. Previous laser systems could not etch a particularly good number of screen lines. The operating CO2 laser operates at a wavelength of about 10 microns and is used for a limited line range. With the emergence of a new generation of laser -- YAG laser, this limitation no longer exists. Because wavelengths as short as 1 micron make it possible to produce smaller dot sizes. Therefore, it can be assumed that the shorter the laser wavelength, the higher the resolution. The latest YAG laser system is equipped with a "multi hit" device, which enables it to etch holes in a series of finer steps. The final hole wall is finer and the hole profile is steeper

The hole formed by CO2 laser is produced by strong pulse. The laser beam impacting the ceramic coating is partially reflected and partially absorbed by the material. This leads to two different processes:

* melting

* volatilization of ceramic coating

one feature of CO2 laser is that the melted ceramics accumulate on the hole wall and can be removed only after special trimming. The etching with YAG laser is mainly a volatilization process without melting. This provides a smoother and more uniform etching effect for high-quality printing

this does not mean that YAG laser is the only one used in the future. Their low energy is not suitable for the production of rough corrugated rollers with a corresponding high number of holes. Therefore, using YAG laser to produce such a roller is not economical. The minimum limit of YAG laser is 160-200l/cm, but it should be mainly used in the production of particularly high line

the diamond polisher will also make the final special trimming of the roller to remove the slightest uneven part. In this way, each roll can be used immediately without the previous running in process. Each metal embossed roller needs to be accurately controlled during manufacturing. The diameter, focusing, etching depth, theoretical hole size, production quantity, sequence, customer and production data are clearly marked on the certificate of conformity of the embossed roller (which accompanies the whole transmission process). (end)

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