Ink fountain peripheral automation system
Due to the disadvantages of unstable ink control and labor-intensive operation around the ink fountain, the structure of a general printing machine requires considerable effort to achieve high-quality printing.
In order to change this situation, our company has proposed the concept of automation and labor saving, and successfully developed the J-COLOR system. It uses an ink transfer roller structure (ie, IPC system): an ink preset control system to automatically control the ink supply and Through the AFC system (automatic ink fountain cleaning device) and ACC system (automatic ink supply device), it becomes a system that can fully automate the periphery of the ink fountain.
(1) The concept of ink transfer roller
IPC: The ink fountain of the ink preset control system is equipped with a plate, or a triangular ink fountain can be used to keep the ink fountain gap fixed, and the ink transfer roller on the printing machine is designed as a split type ink transfer roller. The contact length controls the amount of ink supplied.
The biggest feature of this system is: compared with the adjustment of the ink fountain blade gap, the method of separately controlling the amount of ink supply through the contact length of the split ink transfer roller and the main ink roller can achieve higher control accuracy.
The gap of the ink fountain of the common ink key blade is 0mm ～ 0.2mm, within this range can be adjusted according to the proportion of 0% ～ 100%, but to adjust 1%, the gap opening of 0.002mm (2 microns) must be guaranteed, Even if the mechanical precision is improved, it is extremely difficult to control 0.002mm. In addition, the material of the ink fountain will also undergo thermal expansion (Note: iron: linear expansion ratio 12.1mm × 10-6, temperature change of 10 ° C, length 50mm: expansion and contraction of 6 microns.) And gap adjustment parts due to changes in time-phase Due to the effects of ink clogging, blade wear, etc., errors will inevitably occur between the computer control data and the actual gap adjustment during printing, which requires periodic adjustments.
In addition, when the ink amount of a certain part is to be increased or decreased, the ink key blade method also needs to adjust the adjacent two sides of the ink key, and the ink transfer division roller method does not require this operation.
The contact length of the main ink roller is controlled by the split type ink transfer roller. For example, "offset offset press", the contact length can be adjusted within the range of 0mm ~ 150mm, and the contact interval can be adjusted arbitrarily. In terms of adjustment difficulty, the adjustable gap of the ink key blade method is 0mm to 0.2mm, and the control range of the ink transfer roller method can reach 150mm. The simple comparison calculation result is 0.2mm / 150mm, which is 1/750. Compared with the adjustment of the ink fountain gap in units of a few microns, it is undoubtedly more convenient to control the contact length of the ink roller in millimeters, and it can achieve higher precision control.
Similarly, when adjusting the size of the pattern by 1%, the transfer ink dividing roller needs to be in contact with the main ink roller by about 1.5 mm, but it is accumulated and stored until it is not less than the pressure roller gap, which can be controlled by intermittent operation.
When using the ink preset system with gap control method, there are 1. the change of ink viscosity to density; 2. the relationship between ink fountain gap and ink supply amount; 3. the relationship between density instability caused by speed change, and due to the difficulty of adjustment and problems Or the degree of experience of the operators varies. To this end, our company constantly seeks to improve, the following to introduce the J-COLOR system to solve these problems? Q method. [next]
â—† Influence of ink viscosity on concentration
When using the ink key blade method, usually a large amount of ink is added to the ink fountain during the printing process. In fact, only the ink above the ink fountain can be stirred and circulated. When the ink fountain gap is close to 0, because the ink is affected by water, the phenomenon that ink cannot be dropped easily occurs, resulting in a decrease in printing density. For this, the operator needs to open the gap of the ink fountain.
Since the ink fountain gaps are different, the amount of ink supplied will be affected by the internal pressure of the ink. To this end, it is necessary to add ink at any time, so that the amount of ink in the ink fountain reaches about 60%.
When using the ink transfer division roller method, because the ink fountain gap is fixed, the ink supply will not change due to the size of the gap, and the fixed amount of ink will evenly flow out from the gap, even if the ink volume in the ink fountain is as low as about 30mm. It will still circulate and maintain the ink characteristics during ink supply, and there will be no uneven printing density due to changes in ink characteristics. The thickness of the ink film on the ink roller is kept fixed, and the contact length of the ink roller can be adjusted in units of accuracy of 1 mm, so it is not easy to cause shade errors.
â—† Relationship between ink fountain gap and ink supply
The ideal ink supply control is: the increase in ink supply is proportional to the opening of the ink fountain gap (see figure: red line). However, when the ink key scraper method is used, the amount of ink supplied is parabolic. (See picture: blue line)
As can be seen from the figure, when the pattern area is small, although the ink opening is extremely small, if the amount of ink supply becomes larger, the smaller the gap, the more difficult it is to adjust the amount of ink. When using the ink key scraper method, the ink fountain gap must be set to more than 50 microns (equivalent to 25% of the pattern area), otherwise it cannot be guaranteed to provide an appropriate ink density.
However, as mentioned above, it is very difficult to adjust the gap below 50 microns. Therefore, when printing micro-patterns, waste pages should be specially set to ensure a certain degree of ink supply gap and stabilize printing. When adopting the ink transfer and dividing roller method, the ink fountain gap can be set uniformly within the range of 0.12mm to 0.23mm, and the control range is close to the ideal printing state. Even for a small pattern area, the ink fountain gap is still fixed. By controlling the contact length of the roller to a few millimeters, ink supply can be stabilized.
◆ Speed ​​tracking and printing density
When the ink key blade method is adopted, when the printing speed changes from low to high, even if the gap of the ink key blade is consistent with the pattern data, an ink film thickness error and density unevenness will occur. This is because as the speed increases, the amount of ink supplied in the gap will be reduced due to the pressure of the ink roller and the internal pressure of the ink fountain. The effect is not easy to ink. As a result, the difference in ink fountain gap opening causes uneven density, making it difficult to achieve stable density adjustment.
When split ink transfer roller method is adopted, the ink fountain gap is uniform and the ink film thickness is fixed. Therefore, it is not easy to change the density due to the influence of the internal pressure of the ink. By controlling the contact length between the roller and the ink fountain roller, ink can be supplied according to the pattern data. In addition, it has a speed tracking function, so even if the speed changes, there will be no density unevenness; it can also be set by parameters to enable stable printing.
(2) Characteristics of IPC system
â— Initial ink supply
The system has the ink leveling function. From the beginning of printing, it can supply ink stably according to the pattern area ratio data. It has the ink leveling function that supplies ink on the entire roller before printing, and the pattern ink leveling function that supplies ink in advance according to the pattern area ratio. The density can be adjusted to the best after the trial printing. Since the printing can be stable after the trial printing, it can reduce the consumption of paper and ink, and also help shorten the production preparation time.
â— Inking structure
When using the usual ink fountain screw method, a small amount of ink will be supplied even when the pattern ratio is 0%. During printing, ink accumulation will occur at both ends of the ink leveling roller, resulting in a greater density at both ends. In the case of the ink transfer division roller method, the ink supply is completely stopped at 0%. But even so, sometimes there will be a situation where the remaining ink accumulates on both ends of the roller after the ink is evenly oscillated. At this time, the ink will flow to the rollers at both ends of the ink transfer dividing roller, but the ink can be transferred to the ink fountain by the side scrapers (barrier plates) installed at both ends of the ink fountain roller and the attached ink scrapers at the front end. With this ink return structure, the ink concentration can be kept stable. [next]
The side plate and the squeegee also have a feature. When printing a minute pattern, install a squeegee on the side plate to be used to absorb the surrounding ink, which can achieve a stable concentration with a small amount of ink.
â— Prevent excessive ink emulsification and stable printing quality
During offset printing, the ink at both ends of the ink leveling roller is easy to accumulate ink, and the IPC system is provided with side plates and squeegees at both ends of the ink fountain roller, so that the ink flowing back from the ink leveling roller is forced to return through the ink transfer roller, and by The ink scraper scrapes, so ink will not accumulate at both ends of the roller, and the ink will return to the ink fountain. Since no residual ink is left at both ends of the roller, the ink can be prevented from being excessively emulsified, and the printing quality on the entire surface is stable. In addition, as mentioned above, the ink fountain gap can reach 0mm ~ 0.23mm and fixed, so there will be no ink blocking. Moreover, because of the structure of stable ink supply according to the set ink supply amount, the water in the water tank will not be transferred to the ink fountain, so the ink characteristics in the ink fountain will not change, which is also a major reason for preventing excessive emulsification.
â— Computer control
In order to adapt to various conditions of the printing press, our company has set various parameter functions in the control system. In general, the density becomes lighter as the speed becomes faster, but the ink transfer roller can be set by parameters to correct the amount of ink supplied as the speed of the printing machine changes. In addition, it also has the function of correcting the% density of the printed pattern, and the ink color can be easily adjusted through the touch screen operation. The concentration can also be adjusted in units of doctor blades, so fast fine-tuning can be achieved.
After the production is completed, the detailed printing data such as ink supply and parameter correction values ​​will be saved in the computer. The repeat printing function is based on the principle of the fixed gap of our company ’s IPC system. Only the data can be retrieved to reproduce the same printing and improve the printing preparation. speed. Help to shorten the time and reduce the loss of printed sheets.
(3) Features of AFC automatic ink fountain cleaning system
AFC (Automatic Fountain Cleaning: Automatic fountain cleaning device)
There is a gap between the main ink roller of the IPC and the ink fountain. Use this gap to penetrate the polyester film or coated film, tighten and cover the ink fountain, and roll up the film by the motor drive to reach the ink fountain The purpose of automatic cleaning is the AFC system. When changing colors, just roll up the film and clean the side plate and ink scraper to clean the ink fountain. In addition, since there is no need to supply ink to the ink fountain excessively, there is little ink loss. The cleaning time is only about 1/3 of the traditional way, which can improve the operation efficiency.
(4) ACC robot automatic refilling system
The ACC (Automatic Cartridge Replacement Device) system can automatically add ink from the ink cartridge installed next to the ink fountain. Through the laser sensor to detect the amount of ink, and on the basis of the correct ink, to achieve automatic robot ink. From automatic ink addition to color change, all operations are automated.
Through the complete introduction of IPC, AFC and ACC systems, complete automation around the ink fountain can be achieved.
(5) Future development
In order to achieve ink supply stabilization and improve accuracy, our company is beginning to develop and add new parameter functions in computer control. Through on-site investigation of customers, increase the functions and precision that customers really need in products, and strive to achieve better printing quality. Another feature is that by reducing paper consumption and reducing factory waste, CO2 emissions can be reduced. As a new development, our company also plans to develop products that transmit ink density management data to IPC through online communication and control the amount of ink supplied based on this information. As a result, a new IPC with a concentration correction function can be realized.
With the introduction of these J-COLOR device solutions, our company is determined to fully automate printing operations in the future. Our company is willing to contribute to reducing the labor load of operators, improving operating efficiency and protecting the environment (reducing CO2).
(6) Delivery performance
In the metal printing industry, our company's sales to Japan and other countries totaled about 1,800 sets. In the paper printing industry, the total performance of our company in the commercial form printing, sheet printing, sticker label, and DVD printing industries has reached about 1200 sets. In recent years, the IPC system of our company has been basically equipped on new machines of large-scale commercial form printing companies in Japan.
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