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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.
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.