The centralized automatic ink supply system is greatly reduced due to the use of a high-pressure single-tube conveying scheme that matches the nature and flow characteristics of the ink, and a variety of quantitative standard packaging. It is equipped with electronic automatic weighing, automatic ink level detection, and a safe and reliable alarm device. The cost of printing production, without environmental pollution, meets the requirements of the development of the printing industry, and the scope of application has expanded rapidly. Newspaper printing, commercial rotary printing and other fields have gained initial popularity, and packaging printing, publishing and printing are gradually being accepted.
The choice of ink packaging The choice of ink packaging is the primary issue of building an ink supply system. It will directly affect the degree of future application of the ink supply system and the choice of product brands and varieties. It is a limiting factor for the supply of raw materials.
At present, the ink packaging options of the centralized ink supply scheme are relatively broad. Most ink factories can already provide standard packaging solutions from 2kg to 2000kg, such as 2kg, 15 kg, 200 kg, 1000 kg, 1500 kg, 2000kg, etc., and can also provide large tanks of 20 tons or 30 tons of ink storage Program. At present, all major equipment suppliers also have standard equipment to match it, with mobile, fixed and other solutions. In this way, users can choose the solution that suits them according to usage requirements, space location, ink requirements and management requirements.
The ink consumption requirement is the main factor that determines the ink specifications and then determines the configuration of the ink supply system. Taking the printing industry as an example, manufacturers with a daily printing volume of less than 500,000 pairs of openings should mainly consider using a 15 kg mobile system. This system is easy to operate, has a small footprint, and can be easily moved. It is a good choice for small units. For manufacturers with a daily production capacity of 500,000 to 2 million, or a large printing plant that implements single-unit ink supply, consider using a 200kg standard cartridge. This system is easy to use and clean, with moderate packaging and good airtightness. Both transportation and handling It is more convenient, and it is easy to switch between different ink brands. For black ink with a large amount of ink, you can consider using 200kg double pumps and two machines to work or install a 1 ton system to solve the problem of excessive black ink consumption. For manufacturers with a daily production capacity of more than 2 million pairs of openings, and want to concentrate a set of equipment to supply ink to all machine systems, the 1 ton standard ink tank and large ink tank can be considered, so that people can be concentrated on ink supply Management, reduce the trouble of replacing ink cartridges in the workshop, and implement professional management to improve work efficiency.
The selection of the ink supply system is related to the flexibility of ink procurement and the convenience of management in the future, which requires coordination and cooperation in all aspects.
Most of the operating pressure is determined by the centralized ink supply system, which is a single-tube high-pressure system. The higher pressure is a common feature of these systems, which is also determined by the characteristics of the ink. The ink has larger viscosity and high thixotropy, which is completely different from the transportation of water and air with high fluidity and high compressibility. It is precisely because of the high-pressure system that the pipeline can be selected within a relatively narrow range, which is applied to a longer conveying distance and get rid of the shortcomings of the long-term circulation operation of the original double-pipe system.
The size of the operating pressure is determined by the structure and use requirements of the system. Excessive pressure will greatly increase the system cost, resulting in unnecessary waste. Some systems claim to reach a pressure of more than 30MPa. In fact, this is not necessary at all. The pressure provided by the ink pump is generally below 14 Mpa. In addition, the consideration of safety factor does not exceed 21Mpa, and the domestic transmission distance is also short. If the pressure is too low, the ink supply will be insufficient, and the equipment will not run smoothly or even be blocked. Under normal circumstances, the operating pressure of the pipeline system within 150m can fully meet the requirements of about 6 ~ 10Mpa. The factors that affect the operating pressure are:
1. Conveying distance The conveying distance is the main factor that determines the ink supply pressure. The longer the conveying distance, the greater the operating pressure. If it is within 200m, 10Mpa pressure is completely sufficient.
2. Pipe thickness: This refers to the diameter. The thicker the pipeline diameter, the pressure can be reduced accordingly under the same end outlet flow requirements.
3. Pipe elbow and diameter reduction: Both the elbow and the diameter reduction will block the flow of ink. The more elbows and the more diameter changes in the pipeline system from the beginning to the end, the greater the operating pressure. . It should be noted that the effect of diameter reduction on the flow is an order of magnitude higher than that of the elbow. Simultaneously. Special attention should also be paid to the process quality of pipe fittings such as elbows and bent valves. Many lower-quality pipe fittings have a small internal diameter, and there are serious diameter changes in the internal structure.
4. Pipe: The quality of the pipe is an important factor that determines the resistance of the ink to flow in the pipeline. The material of the stainless steel pipe, cold drawn seamless steel pipe, high-grade high-pressure plastic pipe and other pipe fittings and the ink have a large difference in molecular weight. Need to consider. The roughness of the inner diameter is also an important factor that determines the flow resistance. The problem of excessive flow gap between the distal and proximal ends in many systems is mainly due to the selection of lower quality pipes. Therefore, in general, the better the pipe material, the lower the pressure.
5. Ink supply speed requirements: This is not difficult to understand. To make the ink output larger, the pressure needs to be higher.
Pipeline material and connection scheme The current status of China's pipe industry, the choice of pipework and connection scheme is the main factor restricting the pressure of the system. In foreign systems, the cold drawn seamless steel tube plus ferrule connection scheme is generally adopted. It has moderate cost, wide pressure range, good quality of inner diameter of pipeline, less diameter change, beautiful appearance, and rapid construction. It is the ink supply The best choice for system piping. However, the cost of importing the same system into China is far higher than that of ordinary users. Therefore, except for the introduction of a small number of randomizers, this solution is rarely used. At present, due to the low precision of the outer diameter of the domestic seamless cold-drawn steel pipe, it is not possible to use a ferrule-type connection. Therefore, at present, there are many compromises in the variety of pipe materials used in the domestic ink supply system.
At present, the pipelines of the centralized ink supply system used in China mainly include FP-R pipe heating welding, seamless steel pipe welding, seamless steel pipe welding processing pipe head plus ferrule connection, precision cold drawn stainless steel tube ferrule connection and other programs. Recently, the Shenyang North Factory has solved the problem of low precision of domestic seamless pipes that cannot be connected by ferrules by customizing the ferrules. It has basically solved the connection problem of domestic pipes, which can meet the needs of ordinary users, and the cost is only 1/3 of the imported pipes. about. Shanghai Fuyang Co., Ltd. adopted a customized pipeline to solve the connection problem. Although the quality of PP-R pipe is higher only from the perspective of inner diameter quality and molecular force, its pressure resistance generally does not exceed 5Mpa, and it is only suitable for stand-alone systems with shorter pipe lengths.
There are two problems in the welding scheme. First, the pressure resistance is low, and the system pressure selection is small. If the welding quality is not guaranteed, the pressure will be lower. The operating pressure of the welded pipe system is preferably controlled below 5Mpa; second, the inner diameter quality is low. Poor finish, large flow resistance, and construction fire problems are also unsafe, so it has been rarely used. Precision stainless steel tube ferrule connection is a better solution, but the cost is too high, the cost per meter is more than 200 yuan, and it is still used less.
The design of the pipeline is a key factor in the performance of the ink supply system. It should be based on the principle that the pipeline is as short as possible, the elbows should be as few as possible, and the diameter change should be avoided as much as possible. Before construction, the pipeline scheme should be continuously optimized to make the pipeline application reasonable. Everyone has a common understanding: as the flow rate in the pipeline becomes smaller, the closer to the end diameter, the smaller the diameter. In fact, this theory is not applicable to inks with high viscosity. The pressure loss of a variable diameter is much greater than that of an elbow. The design should reduce the use of variable diameter as much as possible. Due to the large pressure loss in the ink delivery process, the closer to the end, the smaller the pressure, so it should not be casually reducing the main pipe diameter.
The selection of pipe diameter is also a very critical issue. Recently, we found that some of the ink supply system pipelines installed earlier are below DN32, and the transmission distance is long. The ink supply flow rate is small when used, which cannot meet the use requirements. Due to the high viscosity of the ink and its high thixotropy, if the pipeline is too thin, the flow of ink, especially the initial flow, will be very difficult.
Selection of ink pump parameters
The current centralized ink supply system generally uses a pneumatic plunger pump. In the final analysis, the ink pump is the heart of the centralized ink supply system. It is the top priority in determining system performance and should be given sufficient attention. Many of the systems installed in the early stage were either operating at too low a pressure or the amount of ink in the pump was too small, and the results were not ideal. Some key parameters of ink pump:
1. Pump ink pressure: Pump ink pressure is a key parameter of the ink supply system. It is also the core technology of high-pressure centralized ink supply technology. The identification of general equipment is expressed by the pressure transmission ratio (under RANSMISSION), such as 16: 1, 20: 1, etc., and its calculation formula is: operating pressure = input compressed air pressure * pressure transmission ratio. The air pressure provided by the air supply system is generally about 0.7Mpa, then for the 16: 1 ink pump, the maximum operating pressure can reach 11.2Mpa. The operating pressure can be adjusted by adjusting the intake pressure. Of course, the operating pressure is also limited by the rated pressure of the pipeline system. The maximum pressure of the system adjustment must not exceed the maximum pressure of the pipeline system (safety factor 1.5). If the operating pressure is too low, the flow rate of the ink outlet will be reduced, and there will be no ink output when the pressure loss is lower than the pipeline. The choice of pressure is also directly related to the fluidity of the ink. The better the fluidity, the lower the pressure. This is why the pressure transmission ratio of black ink pumps in many systems is lower than other colors. The pressure of the ink pump, that is, the pressure transmission ratio is the main factor that determines the price of the ink pump. Neither the pressure transmission ratio that is too low for saving money, nor the excessively large pressure transmission ratio can be used blindly in pursuit of spare power. Considering the current situation in China, it may be appropriate to select a pressure transmission ratio of about 12 to 20.
2. Pump ink volume: The pump ink volume is another important parameter of the ink supply system, but it is often overlooked by many users. Many early systems were not as effective as they were used, largely because they did not require pump ink volume or excessively low prices. This is due to the use of a lower pump volume. The amount of pump ink is another key parameter that determines the price of the ink pump, which should be selected according to the demand for use and the speed of ink use. Generally speaking, the larger the ink consumption, the larger the unit configuration, and the higher the ink supply speed requirements, the larger the amount of ink required. As far as the manufacturer's published parameters are concerned, the pump ink volume has a direct nominal, most of which is marked as the pump ink volume per double stroke, which can be directly referred to. We can also determine according to the appearance diameter of the cylinder. Under a certain pressure transmission ratio, the larger the cylinder diameter, the greater the amount of ink pumped. At the same time, under a certain cylinder diameter, the smaller the pressure transmission ratio, the greater the amount of ink pumped. In terms of the specific quantitative relationship, the pump ink volume is inversely proportional to the pressure transmission ratio and proportional to the cylinder cross-sectional area (the square of the radius).
Order and installation issues Currently, domestic manufacturers of centralized ink supply technology equipment mainly include Taichung Company, Gurit Company, Pranato Company, Lincoln Company, Shenyang North Universal Printing Machinery Equipment Factory, etc. There are a full range of products from ink pumps to pipelines. Centralized ink supply technology is not like ordinary equipment products. The buyer and seller are purely supplier and user relationships, and there are more or less ink supplier factors in the middle. At present, the available methods of centralized ink supply mainly include the introduction of the ink supply system when the equipment is introduced, the ink factory ordering the ink supply system for the user, and the user self-ordering. At present, many user systems are ordered and installed for the user by the ink factory (Of course, ink factories are conditional), foreign countries used to do so in this way. The ink factory is an equipment orderer rather than a direct user, and how users monitor the technical indicators of the equipment becomes a key issue. The main reason for the unsatisfactory use of many systems is the insufficient monitoring of the order of the system, and because users do not fully understand the supply side, it is often difficult to accurately grasp the technical parameters, and future maintenance is also a big problem. It is for this reason that many printing plants in foreign countries have begun to order ink supply systems directly, and some domestic users have also begun to adopt this method.
In addition, it should be noted that the installation method of the ink factory requires a long-term order contract to be signed with it. If you are not satisfied with the ink quality, you should choose this method carefully. Adding the ink supply system directly when importing equipment from abroad will make the ink supply system and the printing machine cooperate well. Due to the tax exemption, the price is also acceptable and a good choice, but the system is only suitable for the single machine of the imported equipment.
The installation quality of the ink supply pipeline is the basic guarantee for the reliable operation of the system. Since the operating pressure of the pipeline is much higher than other water and gas pipelines, special attention should be paid. The installer must have a construction plan suitable for the characteristics of ink supply, and must have a guarantee contract clause; after the installation is completed, a pressure test should be carried out. In the installation design process, many users expect the ink supply system to have a high degree of automation and accurate measurement in order to achieve the goal of improving management quality. For example, the automatic monitoring of the ink tank liquid level, the automatic control of the ink volume of the ultrasonic ink fountain, the measurement of the ink volume of the large tank, etc. Some users also need the flow measurement of each ink fountain. This is understandable and also in line with today's development trend. But when choosing these equipments, it should be noted that the first function of the ink supply system, ink supply, must be fully ensured. This is the main investment body of the construction. Most of these automation and metering equipments are very expensive. For example, the investment of an ink fountain unit in the ink fountain ink automatic control system is several thousand yuan. Due to the flow characteristics of ink, the requirements for measuring instruments are very high, but the accuracy is not ideal, and the price It is expensive, and needs to be considered carefully. The filter is an indispensable part of a complete ink supply system. It is installed between the ink pump and the pipeline, and mainly plays the role of protecting the pipeline. It has certain significance for ensuring the quality of the ink supply, service life, and system safety.
For many users, the centralized ink supply system is a brand new technology. In order to ensure the system's usage, all parties concerned need to analyze and design the system carefully, and users need to fully understand the technology of the relevant manufacturers.
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