Recently, we visited a number of corrugated box printing companies and conducted technical exchanges with them. We found that there are still some problems in the operation technology and we should pay attention to them.
Flexo printing belongs to light pressure printing, so taking pressure measures will only backfire by pushing the limited amount of ink to areas that do not need ink. Excessive flexo pressure is the result of hard mouth (wild ink), flash, stencil, etc. The main reason. How to control the pressure, the key lies in the operation adjustment. Adjustment is actually to control the compression deformation of the printing plate. The smaller the deformation of the printing plate, the higher the printing quality.
In the printing process, there are 3 pressure points (actually 3 embossing strips), namely the ink fountain roller and the metal anilox roller, the metal anilox roller and the plate cylinder, the plate cylinder and the impression cylinder. These three pressure points are all very important in terms of operation technology and should be printed under controlled conditions. At present, some domestic companies rely on experience: some pressure points are out of control during printing; some even print under the wrong operating conditions, and the quality of the printed matter is not good.
Correct control of the printing state should start from the following aspects.
1. The contact pressure between the ink fountain roller and the metal anilox roller can be slightly larger than the pressure of the metal anilox roller and the plate cylinder and the plate cylinder and the impression cylinder. The role of the ink fountain roller is to squeeze out the ink on the surface of the metal anilox roller, so the pressure can be slightly larger. The control method is as follows:
With a 0.10 mm thick gauge, stuff it in at the point of contact, plug it a few more points, and stuff it under tight conditions. The kraft paper can also be cut into strips of 60-80 mm and placed on the contact points. The length of the anilox roll is 4 to 6 for long and 3 for short. Adjusting the ink fountain roller to the kraft paper can be pulled under relatively tight conditions. If it is easy to pull it up or it is easy to insert the thick gauge into it, there is a gap between the two, which is abnormal. The ink fountain roller and metal anilox roller must work under contact. At present, some companies use high-quality anilox roller lines for printing, reaching 180 lines/inch or 250 lines/inch. When printing color blocks and large letters, the amount of ink is not enough, so operators often use ink rollers to increase ink fountains. Roller and anilox roller gap method to increase ink supply. But once there is a gap, it will lose the role of the metal anilox roller for quantitative ink supply, otherwise we can completely replace the metal anilox roller with a metal light roller. Why use an expensive metal anilox roller? Therefore, the use of metal anilox roller must be With the concept of "quantitative" ink supply, it is impossible to adjust the amount of ink with gaps. If there is a gap, the amount of ink will be poorly controlled. If printed on the ground, a corduroy-like streak will appear, and the cable version will produce a color difference. If the ink fountain roller and the metal anilox roller are under normal contact, the ink on the metal anilox roller net wall still cannot be squeezed out, indicating that the viscosity of the ink is too high and the ink viscosity should be adjusted.
2. The contact pressure between the metal anilox roller and the plate cylinder should be light, light to what extent? Why lighter? How to control? The anilox roller transfers ink to the printing plate, printing plate can be printed after receiving ink, if the anilox roller does not contact Into the printing plate, the printing plate can not get ink, printing can not be carried out. How should the anilox roll be in contact with the printing plate in order to meet the light pressure requirements? The plate is mounted on the surface of the plate cylinder. The thickness of the plate is known, for example, the thickness of the plate is 3.94 mm and the thickness of the lining is 3 .05mm, double sided tape is 0.11mm, hanging polyester is 0.10mm, total thickness is 7.20mm. According to the requirement of lighter pressure, it is better that the two rollers are in tangential contact, that is, the distance between the metal anilox roller and the plate cylinder is kept at 7.20 mm. However, due to the fact that the anilox roller, the plate, and the roller have a positional error , so tangential state is impossible. After testing the anilox roll misalignment and radial jump of 0.02~0.04mm, the plate cylinder diameter jump is 0.01~0.02mm, the plate thickness error is 0.02mm, the maximum error is 0.08 mm, plus a printing pressure of 0.02 mm, the total is 0.1 mm. As long as the anilox roller is fully accessible to the printing plate, the ink in the anilox roller can be transferred to the printing plate, and the requirements for ink transfer are achieved. Therefore, with a 6 mm feeler gauge and thickness gauge, the distance between the anilox roller and the plate cylinder is controlled to be 7.10 mm, which can meet the requirement of light pressure.
In the units I visited, the pressure between the metal anilox roller and the plate cylinder was significantly greater than 0.1 mm. In fact, the pressure is too great, not only affects the service life of the printing plate, but also is very unfavorable to improving the printing quality. The anilox roller is in contact with the printing plate, and the printing plate is deformed to meet the light pressure requirement. If the pressure is too high, the anilox roller first contacts the side of the printing plate during printing, and the ink is compressed after the printing plate is deformed. As a result, the front of the printing pattern and the text appears hard (wild ink) and the burrs are serious. At present, quality issues in this area can be observed on many prints. When printing the cable version, the pressure is too large to produce a paste, so the contact pressure must be light. As mentioned above, generally, the pressure should be controlled at 0.1 mm. The user still has to be flexible in actual operation depending on the actual situation. If the accuracy of the machine is poor, the pressure can be appropriately increased; otherwise, the pressure can be reduced.
3. In theory, the contact pressure between the plate cylinder and the impression cylinder should also be light, but in fact it is not easy to do in the printing of corrugated boxes, but in the mind of operators must establish a "light" idea. We must strive to achieve light pressure. The distance between the plate cylinder and the impression cylinder is the total thickness of the plate plus the thickness of the corrugated cardboard. The total thickness of the plate can be controlled as described above, but the thickness of the corrugated cardboard is difficult to control. Therefore, whenever I had the opportunity, I called for attention to the quality of corrugated paper. The printing quality of corrugated boxes is closely related to the thickness and flatness error of corrugated board itself. The corrugated paper in the printing base is the worst, not only the thickness of a sheet of paper is much different, but also the thickness and the level of corrugation of the same sheet of paper are very large. In printing, it is required to meet the thickness requirements of all corrugated boards to achieve good quality. It is difficult to control.
How to control the gap between the plate cylinder and the imprinting cylinder?
Clearance = total plate thickness + corrugated board thickness - 0.5-0.1
In the formula, 0.5 is the error amount of the corrugated board thickness measured, and 0.1 is the aforementioned error amount of the roll and the plate material; this 0.6 mm is to control the printing according to the quality and other errors of the corrugated board. The reasonable amount of compression. The feeler and gauge are used to control the gap between the plate cylinder and the impression cylinder. Within this control range, it is already possible to ensure that the inked portion of the corrugated paper is completely printed out. However, due to the thickness error of corrugated paper, when printing thick corrugated cardboard, the large amount of compression of the printing plate will adversely affect the printing quality. Therefore, to ensure the printing quality, the quality of the corrugated cardboard should be improved as much as possible to reduce the thickness error. If you do not control the operation, you will experience severe hard pressure when you are over-stressed. You will not be able to print on the ground. The ink on the lines will be light and the non-inking edges will appear hard and the ink will be dark. Excessive pressure on the printed cable version will cause the network to enlarge the paste, and three or four percent of the network have hollow dots.
In addition, in the case of school printing, if there is a phenomenon of partial printing, it is better not to adopt a method of increasing the pressure, because although this can temporarily solve the problem of partial printing, most of the rest will be deformed. , not worth the candle. The correct approach should be to use the method of pad plate to solve, that is, according to the actual situation in the hanging film behind the pad.
The same is true for pressure control in flexo flexo presses. However, since the inking device of this flexographic printing machine uses a doctor blade, there is no pressure control problem between the ink fountain roller and the anilox roller, and because of the high precision of the anilox roller and the plate cylinder of the flexible packaging flexographic printing machine, the plate material Thinness and shape error do not need to be controlled at 0.1 mm. Control at 0.03 to 0.05 mm is sufficient. Flexible packaging printing base materials are better, so the gap between the plate cylinder and the impression cylinder (pressure) can be controlled in the following areas: plate thickness + double-sided adhesive thickness + printing base material thickness - comprehensive error -0.02 (mm ), where the combined error value does not exceed 0.05 mm.
Flexo printing belongs to light pressure printing, so taking pressure measures will only backfire by pushing the limited amount of ink to areas that do not need ink. Excessive flexo pressure is the result of hard mouth (wild ink), flash, stencil, etc. The main reason. How to control the pressure, the key lies in the operation adjustment. Adjustment is actually to control the compression deformation of the printing plate. The smaller the deformation of the printing plate, the higher the printing quality.
In the printing process, there are 3 pressure points (actually 3 embossing strips), namely the ink fountain roller and the metal anilox roller, the metal anilox roller and the plate cylinder, the plate cylinder and the impression cylinder. These three pressure points are all very important in terms of operation technology and should be printed under controlled conditions. At present, some domestic companies rely on experience: some pressure points are out of control during printing; some even print under the wrong operating conditions, and the quality of the printed matter is not good.
Correct control of the printing state should start from the following aspects.
1. The contact pressure between the ink fountain roller and the metal anilox roller can be slightly larger than the pressure of the metal anilox roller and the plate cylinder and the plate cylinder and the impression cylinder. The role of the ink fountain roller is to squeeze out the ink on the surface of the metal anilox roller, so the pressure can be slightly larger. The control method is as follows:
With a 0.10 mm thick gauge, stuff it in at the point of contact, plug it a few more points, and stuff it under tight conditions. The kraft paper can also be cut into strips of 60-80 mm and placed on the contact points. The length of the anilox roll is 4 to 6 for long and 3 for short. Adjusting the ink fountain roller to the kraft paper can be pulled under relatively tight conditions. If it is easy to pull it up or it is easy to insert the thick gauge into it, there is a gap between the two, which is abnormal. The ink fountain roller and metal anilox roller must work under contact. At present, some companies use high-quality anilox roller lines for printing, reaching 180 lines/inch or 250 lines/inch. When printing color blocks and large letters, the amount of ink is not enough, so operators often use ink rollers to increase ink fountains. Roller and anilox roller gap method to increase ink supply. But once there is a gap, it will lose the role of the metal anilox roller for quantitative ink supply, otherwise we can completely replace the metal anilox roller with a metal light roller. Why use an expensive metal anilox roller? Therefore, the use of metal anilox roller must be With the concept of "quantitative" ink supply, it is impossible to adjust the amount of ink with gaps. If there is a gap, the amount of ink will be poorly controlled. If printed on the ground, a corduroy-like streak will appear, and the cable version will produce a color difference. If the ink fountain roller and the metal anilox roller are under normal contact, the ink on the metal anilox roller net wall still cannot be squeezed out, indicating that the viscosity of the ink is too high and the ink viscosity should be adjusted.
2. The contact pressure between the metal anilox roller and the plate cylinder should be light, light to what extent? Why lighter? How to control? The anilox roller transfers ink to the printing plate, printing plate can be printed after receiving ink, if the anilox roller does not contact Into the printing plate, the printing plate can not get ink, printing can not be carried out. How should the anilox roll be in contact with the printing plate in order to meet the light pressure requirements? The plate is mounted on the surface of the plate cylinder. The thickness of the plate is known, for example, the thickness of the plate is 3.94 mm and the thickness of the lining is 3 .05mm, double sided tape is 0.11mm, hanging polyester is 0.10mm, total thickness is 7.20mm. According to the requirement of lighter pressure, it is better that the two rollers are in tangential contact, that is, the distance between the metal anilox roller and the plate cylinder is kept at 7.20 mm. However, due to the fact that the anilox roller, the plate, and the roller have a positional error , so tangential state is impossible. After testing the anilox roll misalignment and radial jump of 0.02~0.04mm, the plate cylinder diameter jump is 0.01~0.02mm, the plate thickness error is 0.02mm, the maximum error is 0.08 mm, plus a printing pressure of 0.02 mm, the total is 0.1 mm. As long as the anilox roller is fully accessible to the printing plate, the ink in the anilox roller can be transferred to the printing plate, and the requirements for ink transfer are achieved. Therefore, with a 6 mm feeler gauge and thickness gauge, the distance between the anilox roller and the plate cylinder is controlled to be 7.10 mm, which can meet the requirement of light pressure.
In the units I visited, the pressure between the metal anilox roller and the plate cylinder was significantly greater than 0.1 mm. In fact, the pressure is too great, not only affects the service life of the printing plate, but also is very unfavorable to improving the printing quality. The anilox roller is in contact with the printing plate, and the printing plate is deformed to meet the light pressure requirement. If the pressure is too high, the anilox roller first contacts the side of the printing plate during printing, and the ink is compressed after the printing plate is deformed. As a result, the front of the printing pattern and the text appears hard (wild ink) and the burrs are serious. At present, quality issues in this area can be observed on many prints. When printing the cable version, the pressure is too large to produce a paste, so the contact pressure must be light. As mentioned above, generally, the pressure should be controlled at 0.1 mm. The user still has to be flexible in actual operation depending on the actual situation. If the accuracy of the machine is poor, the pressure can be appropriately increased; otherwise, the pressure can be reduced.
3. In theory, the contact pressure between the plate cylinder and the impression cylinder should also be light, but in fact it is not easy to do in the printing of corrugated boxes, but in the mind of operators must establish a "light" idea. We must strive to achieve light pressure. The distance between the plate cylinder and the impression cylinder is the total thickness of the plate plus the thickness of the corrugated cardboard. The total thickness of the plate can be controlled as described above, but the thickness of the corrugated cardboard is difficult to control. Therefore, whenever I had the opportunity, I called for attention to the quality of corrugated paper. The printing quality of corrugated boxes is closely related to the thickness and flatness error of corrugated board itself. The corrugated paper in the printing base is the worst, not only the thickness of a sheet of paper is much different, but also the thickness and the level of corrugation of the same sheet of paper are very large. In printing, it is required to meet the thickness requirements of all corrugated boards to achieve good quality. It is difficult to control.
How to control the gap between the plate cylinder and the imprinting cylinder?
Clearance = total plate thickness + corrugated board thickness - 0.5-0.1
In the formula, 0.5 is the error amount of the corrugated board thickness measured, and 0.1 is the aforementioned error amount of the roll and the plate material; this 0.6 mm is to control the printing according to the quality and other errors of the corrugated board. The reasonable amount of compression. The feeler and gauge are used to control the gap between the plate cylinder and the impression cylinder. Within this control range, it is already possible to ensure that the inked portion of the corrugated paper is completely printed out. However, due to the thickness error of corrugated paper, when printing thick corrugated cardboard, the large amount of compression of the printing plate will adversely affect the printing quality. Therefore, to ensure the printing quality, the quality of the corrugated cardboard should be improved as much as possible to reduce the thickness error. If you do not control the operation, you will experience severe hard pressure when you are over-stressed. You will not be able to print on the ground. The ink on the lines will be light and the non-inking edges will appear hard and the ink will be dark. Excessive pressure on the printed cable version will cause the network to enlarge the paste, and three or four percent of the network have hollow dots.
In addition, in the case of school printing, if there is a phenomenon of partial printing, it is better not to adopt a method of increasing the pressure, because although this can temporarily solve the problem of partial printing, most of the rest will be deformed. , not worth the candle. The correct approach should be to use the method of pad plate to solve, that is, according to the actual situation in the hanging film behind the pad.
The same is true for pressure control in flexo flexo presses. However, since the inking device of this flexographic printing machine uses a doctor blade, there is no pressure control problem between the ink fountain roller and the anilox roller, and because of the high precision of the anilox roller and the plate cylinder of the flexible packaging flexographic printing machine, the plate material Thinness and shape error do not need to be controlled at 0.1 mm. Control at 0.03 to 0.05 mm is sufficient. Flexible packaging printing base materials are better, so the gap between the plate cylinder and the impression cylinder (pressure) can be controlled in the following areas: plate thickness + double-sided adhesive thickness + printing base material thickness - comprehensive error -0.02 (mm ), where the combined error value does not exceed 0.05 mm.
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