No matter how high the print quality is today, ink fading sometimes remains a problem. Our R&D engineers have considered how to further improve quality issues, and they also found solutions.
Prior to this, Roland 700 ink supply device has already had the ability to ensure stable printing. Including the stepless adjustable horizontal stroke of the ink roller, adjustable ink on the “job†of the printing roller, and most importantly, it can be controlled from the center of the PECOM printing machine, changing the ink at an angle increment of 30 degrees. The starting angle of the ink in the roller.
A large number of tests were conducted to determine the impact parameters that minimize ink fading. As a result, it was found that only the ink oscillating roller directly in contact with the stencil roll had a significant effect on ink fading. The improvements made here have halved the density of the ink on the printed sheet, which is very light and barely visible to the naked eye.
Modern printing presses, such as the Roland 700, have reliable engineering and advanced control and adjustment techniques to suit the highest requirements. However, the problem of density changes on printed sheets may occasionally appear in some special cases. To this end, manroland's R&D engineers were instructed to examine the parameters that affect ink fading. We have been able to change the initial ink jetting angle of the ink fountain roller from the PECOM press center to reduce the ink fading phenomenon, but the purpose of the task is to determine the cause and related factors, thus providing new possibilities for improving the printing effect.
What is Ink Fade "Ink Fade" is the industry term for the change in ink stamping. The word "fade" is used because it usually happens that the ink at the end of the image has a lower density than the front end.
Causes of ink fading?
In the circumferential direction of the plate cylinder, the graphic and non-graphical parts are irregularly distributed. At the same time, the non-printing roller gap also has an effect. Cross-inking affects ink fading.
How the irregularly distributed graphic and non-graphical portions cause ink fading can be explained as follows: The ink roller of the ink supply device forms an ink storage reservoir, which is constantly replenished from the ink fountain by a metering member and an ink roller. The relatively high amount of ink stored in the ink supply device in the ink supply device compensates for the irregular effects described above through the ink passage and a certain width of the ink string.
The printing ink is transferred to the graphic portion of the printing plate by the printing roller. Depending on how much the ink roller "storage" is, more or less ink is transferred to the plate and transferred from the plate to the substrate through the blanket.
Therefore, the following effect occurs: Whenever the non-graphic area does not take ink from the "ink bank," the amount of ink on the ink roller increases. When the printing area is covered with ink, the amount of ink on the ink roller is reduced. The plate cylinder gap forms a relatively large non-graphic area. This results in a “sawtooth†shape in the ink: the ink at the beginning of the print is slightly higher, while the ink at the end of the print is slightly lower.
The design of the transverse cross-inking in the ink supply device can make the ink distribution characteristics on the ink roller smooth, and thus helps to prevent ghosting. However, this necessary and popular feature also has side effects - stringing inks affect ink fading. The printer knows this, because adjusting the starting angle of the ink string will bring about a big change in the degree and development of ink fading, but the exact cause of this effect has never been clarified previously, at least we are concerned about the fading of the ink on the ink. The explanation of the impact is still unknown.
Influencing variables for ink fading include:
The distribution of printed and blank parts on the periphery of the roller, and the image, in addition, do not depend on the quality of the ink used. For example, the ink fountain roller serially inks the starting angle of the entire distance of the series of strokes, such as when the lateral movement is started, the position of the ink fountain roller relative to the pressure printing cylinder is for preventing or minimizing ink fading. Of course, we can only change the variables that can change, and it will not lead to the quality of other important areas.
Which influence variables can be changed?
The image cannot be changed. After all, the printer can print hard-to-print jobs without any problems.
The possibility of changing the nature of the ink is often limited. Ink properties are generally determined primarily by properties such as gloss or print characteristics. There is little preference for inks that do not tend to fade.
The range of ink stringing is very limited. This is because serial ink implements many essential tasks. One of the points is that the metering elements, such as ink spoons, make the different ink zones horizontally uniform (30 mm wide on the manroland sheet-fed offset press). However, the main task of ink stringing is to eliminate the fluctuation of ink supply on the printing roller produced by the image, that is, to generate ghost images. This is the most important task, requiring a certain length of ink stroke, so that there is only a small change here.
The greatest possibility of producing effective changes is provided by the initial angle of ink jetting. This is the best way to eliminate ink fading that has been adopted in the past, and it has the advantage that there is no "side effect" worthy of mention here.
Print test produces new findings Manroland R&D engineers conducted extensive tests to determine the effect of variables that have different effects on ink fading. The evaluation of these print tests resulted in measurements that minimize ink fading problems.
Related to the image, the purpose of the test is to find the answer to the following questions: To what extent does the ink fade due to the roller gap? What degree of image structure is detected? The important question about all ink fountain rollers is: How does the ink string amplitude affect ink fading? How does the initial ink mix angle affect ink fading?
During the printing test, the following influencing parameters were systematically changed:
Plate ink printing speed The structure of the ink supply device String ink Intensity Chain ink Start angle What results can be derived from the print test?
The graphic and non-graphical portions of the plate, as well as the roller gap, can cause the fading of the measured ink density to 3% between the front-end to the end of the print.
Lateral cross-inking has an effect on ink density changes. The qualitative results of these changes only depend on the starting angle of the ink string and the structure of the ink supply device. Only two tandem rollers that are in contact with the printing roller depend on the density characteristics of the respective inks, and the quality depends on the starting angle of the tandem ink. The ink fading that reduces ink mixing is the sum of these two characteristics. The structure of the printing ink and the inking device is of great significance to the degree of ink fading caused by ink reduction. On the other hand, the printing plate and the printing speed have only a slight effect on the degree of fading of the ink reduced by ink stringing.
Improvements in Ink Supply Devices Bring Breakthrough After a thorough study of the variables affecting ink fading, Manroland's R&D engineers successfully reduced ink fading by simply modifying the ink supply.
The FOGRA Institute conducted a formal acceptance test. On October 28th and 29th, 1999, the FOGRA Institute at the offenbach factory conducted a formal acceptance of this improvement.
Printing press: The printing test was conducted on a five-colour Roland 700 with a group of coating units and a delivery table lengthened with an improved ink supply. For comparison, the same test was performed on another six-color Roland 700 that also had a gloss and a delivery table lengthened but did not improve the ink supply. The test version used to test ink fading is a new beta developed by FOGRA for this purpose.
Substrate: Use 135 gsm coated paper for testing.
Ink: Using two inks - black ink, printing density 2.05-2.2, much higher than the 1.80 ± 0.08 given in the FOGRA guide. A spot color, Blue Reflex Blue, with a print density of 1.8-1.9 was also used to test ink fading.
Production speed: FOGRA stipulates that the production speed is 70% of the maximum output speed of the printing press. However, in order to simulate more actual production conditions, a comparative test was conducted at a speed of 87% of the maximum speed of Roland 700, for example, 13,000 sheets/hour.
Plates: This test uses FOGRA's newly designed plates and its design theme is specifically designed to test ink fading. This is a very demanding print test, consisting of mesh patches and solid patches. Its content not only detects ink fading but also detects ghosting.
Ink fades below 85% of the calibration error
When the initial ink mixing angle was 270, the printing ink was not rewound by the printing roller or the three ink rollers were rotated by the printing roller. The ink fades were only 1.4% and 1.7% respectively. Compared with the use of the same method but without the improvement of the ink supply device, the ink fades by more than 50%. This shows that these values ​​are about 85% lower than the 10% ink fade value specified by FOGRA/BVD.
From all these experiments, the printer ink of the improved ink supply device was 30% less faded than the printer without the ink supply device.
Ghost Reduction: This beta also detects ghosting. The improved device will soon become a standard part.
Prior to this, Roland 700 ink supply device has already had the ability to ensure stable printing. Including the stepless adjustable horizontal stroke of the ink roller, adjustable ink on the “job†of the printing roller, and most importantly, it can be controlled from the center of the PECOM printing machine, changing the ink at an angle increment of 30 degrees. The starting angle of the ink in the roller.
A large number of tests were conducted to determine the impact parameters that minimize ink fading. As a result, it was found that only the ink oscillating roller directly in contact with the stencil roll had a significant effect on ink fading. The improvements made here have halved the density of the ink on the printed sheet, which is very light and barely visible to the naked eye.
Modern printing presses, such as the Roland 700, have reliable engineering and advanced control and adjustment techniques to suit the highest requirements. However, the problem of density changes on printed sheets may occasionally appear in some special cases. To this end, manroland's R&D engineers were instructed to examine the parameters that affect ink fading. We have been able to change the initial ink jetting angle of the ink fountain roller from the PECOM press center to reduce the ink fading phenomenon, but the purpose of the task is to determine the cause and related factors, thus providing new possibilities for improving the printing effect.
What is Ink Fade "Ink Fade" is the industry term for the change in ink stamping. The word "fade" is used because it usually happens that the ink at the end of the image has a lower density than the front end.
Causes of ink fading?
In the circumferential direction of the plate cylinder, the graphic and non-graphical parts are irregularly distributed. At the same time, the non-printing roller gap also has an effect. Cross-inking affects ink fading.
How the irregularly distributed graphic and non-graphical portions cause ink fading can be explained as follows: The ink roller of the ink supply device forms an ink storage reservoir, which is constantly replenished from the ink fountain by a metering member and an ink roller. The relatively high amount of ink stored in the ink supply device in the ink supply device compensates for the irregular effects described above through the ink passage and a certain width of the ink string.
The printing ink is transferred to the graphic portion of the printing plate by the printing roller. Depending on how much the ink roller "storage" is, more or less ink is transferred to the plate and transferred from the plate to the substrate through the blanket.
Therefore, the following effect occurs: Whenever the non-graphic area does not take ink from the "ink bank," the amount of ink on the ink roller increases. When the printing area is covered with ink, the amount of ink on the ink roller is reduced. The plate cylinder gap forms a relatively large non-graphic area. This results in a “sawtooth†shape in the ink: the ink at the beginning of the print is slightly higher, while the ink at the end of the print is slightly lower.
The design of the transverse cross-inking in the ink supply device can make the ink distribution characteristics on the ink roller smooth, and thus helps to prevent ghosting. However, this necessary and popular feature also has side effects - stringing inks affect ink fading. The printer knows this, because adjusting the starting angle of the ink string will bring about a big change in the degree and development of ink fading, but the exact cause of this effect has never been clarified previously, at least we are concerned about the fading of the ink on the ink. The explanation of the impact is still unknown.
Influencing variables for ink fading include:
The distribution of printed and blank parts on the periphery of the roller, and the image, in addition, do not depend on the quality of the ink used. For example, the ink fountain roller serially inks the starting angle of the entire distance of the series of strokes, such as when the lateral movement is started, the position of the ink fountain roller relative to the pressure printing cylinder is for preventing or minimizing ink fading. Of course, we can only change the variables that can change, and it will not lead to the quality of other important areas.
Which influence variables can be changed?
The image cannot be changed. After all, the printer can print hard-to-print jobs without any problems.
The possibility of changing the nature of the ink is often limited. Ink properties are generally determined primarily by properties such as gloss or print characteristics. There is little preference for inks that do not tend to fade.
The range of ink stringing is very limited. This is because serial ink implements many essential tasks. One of the points is that the metering elements, such as ink spoons, make the different ink zones horizontally uniform (30 mm wide on the manroland sheet-fed offset press). However, the main task of ink stringing is to eliminate the fluctuation of ink supply on the printing roller produced by the image, that is, to generate ghost images. This is the most important task, requiring a certain length of ink stroke, so that there is only a small change here.
The greatest possibility of producing effective changes is provided by the initial angle of ink jetting. This is the best way to eliminate ink fading that has been adopted in the past, and it has the advantage that there is no "side effect" worthy of mention here.
Print test produces new findings Manroland R&D engineers conducted extensive tests to determine the effect of variables that have different effects on ink fading. The evaluation of these print tests resulted in measurements that minimize ink fading problems.
Related to the image, the purpose of the test is to find the answer to the following questions: To what extent does the ink fade due to the roller gap? What degree of image structure is detected? The important question about all ink fountain rollers is: How does the ink string amplitude affect ink fading? How does the initial ink mix angle affect ink fading?
During the printing test, the following influencing parameters were systematically changed:
Plate ink printing speed The structure of the ink supply device String ink Intensity Chain ink Start angle What results can be derived from the print test?
The graphic and non-graphical portions of the plate, as well as the roller gap, can cause the fading of the measured ink density to 3% between the front-end to the end of the print.
Lateral cross-inking has an effect on ink density changes. The qualitative results of these changes only depend on the starting angle of the ink string and the structure of the ink supply device. Only two tandem rollers that are in contact with the printing roller depend on the density characteristics of the respective inks, and the quality depends on the starting angle of the tandem ink. The ink fading that reduces ink mixing is the sum of these two characteristics. The structure of the printing ink and the inking device is of great significance to the degree of ink fading caused by ink reduction. On the other hand, the printing plate and the printing speed have only a slight effect on the degree of fading of the ink reduced by ink stringing.
Improvements in Ink Supply Devices Bring Breakthrough After a thorough study of the variables affecting ink fading, Manroland's R&D engineers successfully reduced ink fading by simply modifying the ink supply.
The FOGRA Institute conducted a formal acceptance test. On October 28th and 29th, 1999, the FOGRA Institute at the offenbach factory conducted a formal acceptance of this improvement.
Printing press: The printing test was conducted on a five-colour Roland 700 with a group of coating units and a delivery table lengthened with an improved ink supply. For comparison, the same test was performed on another six-color Roland 700 that also had a gloss and a delivery table lengthened but did not improve the ink supply. The test version used to test ink fading is a new beta developed by FOGRA for this purpose.
Substrate: Use 135 gsm coated paper for testing.
Ink: Using two inks - black ink, printing density 2.05-2.2, much higher than the 1.80 ± 0.08 given in the FOGRA guide. A spot color, Blue Reflex Blue, with a print density of 1.8-1.9 was also used to test ink fading.
Production speed: FOGRA stipulates that the production speed is 70% of the maximum output speed of the printing press. However, in order to simulate more actual production conditions, a comparative test was conducted at a speed of 87% of the maximum speed of Roland 700, for example, 13,000 sheets/hour.
Plates: This test uses FOGRA's newly designed plates and its design theme is specifically designed to test ink fading. This is a very demanding print test, consisting of mesh patches and solid patches. Its content not only detects ink fading but also detects ghosting.
Ink fades below 85% of the calibration error
When the initial ink mixing angle was 270, the printing ink was not rewound by the printing roller or the three ink rollers were rotated by the printing roller. The ink fades were only 1.4% and 1.7% respectively. Compared with the use of the same method but without the improvement of the ink supply device, the ink fades by more than 50%. This shows that these values ​​are about 85% lower than the 10% ink fade value specified by FOGRA/BVD.
From all these experiments, the printer ink of the improved ink supply device was 30% less faded than the printer without the ink supply device.
Ghost Reduction: This beta also detects ghosting. The improved device will soon become a standard part.
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