Effect of printing speed on ink transfer

Ink is the basic element for expressing printed images. The thickness of the ink directly affects the level, color, and clarity of the image. Therefore, it is very important to control the transfer of ink. In general, the total ink transfer rate of printing is low, about 38%. The applicability of paper and ink, the suitability of printing plates and blankets, the balance of water and ink, printing plates, and printing pressure all affect the transfer amount and uniformity of the ink. From the point of view of the performance of the printing press, the printing speed can be easily adjusted within a relatively large range, and the printing pressure cannot follow the change automatically according to a certain functional relationship with the speed change. Therefore, the actual production is always used to first fix the printing pressure, and then adjust the amount of ink to adapt to changes in printing speed. Studying the influence of printing speed on ink transfer has certain guiding significance for the adjustment of the amount of ink and water in production, printing speed, and printing pressure.

One, experiment

In order to study the effect of printing speed on the ink transfer amount and ink uniformity, the following test strip was designed: A 40 cm x 1 cm solid field was placed on the fistula area to measure the density of the solid and the uniformity of ink distribution in the axial direction of the roller. . Two 20-step ladders with 5% increments are placed on both sides of the image and are used to measure the dot gain at various levels and calculate the relative contrast. The network used was a circular amplitude modulation network, the number of lines was l75LPl. SBK-B iodine lamp printing machine was used in the experiment. The lamp power was 3500 (TH4200)W. Manual development was performed. The levels on the ladder were clearly structured. With the DigiDensT6CR color reflection densitometer, all levels of error are controlled within ±1%.

The double-sided coated paper with a paper weight of 80g/m2 is printed on a WIN500 single-color offset printing press. The inking system is a ten-roll Z-shaped arrangement. The inking parameters are: the accumulation coefficient Kj=3.41; the uniform ink coefficient Ky=2.49; the inking coefficient Kg=0.92. By observing the reflection of the printing plate during printing, the amount of water is controlled based on dark gray. The control of the printing pressure determines the pressure between the three rollers by adjusting the wheelbase of the roller and observing the width of the ink mark on the blanket. When the pressure is normal, the width of the ink mark of the blanket should be 4±0.5mm, and this pressure is stabilized during the printing process. . To measure the effect of printing speed on ink transfer, print at 1, 5, and 9 (×1000 RPH) respectively.

Experiment l supply ink control: 1 adjust the ink fountain keys to control the amount of ink, set the ink fountain roller teeth to l, with 1000RPH boot version to the field density of l.75, stable after printing 100, from 100 proofs Randomly extracted 10 for the analysis. 2 Print at 5000 RPH for 10 minutes. Take every 2 minutes for a total of 10 samples. 3 Print at a rate of 9000 RPH for 10 minutes, take a sample every 2 minutes, and take a total of 10 pieces.

Experiment 2 Ink supply control: 1 Adjust the ink fountain keys to control the amount of ink, set the number of teeth on the ink fountain roller to be 5, turn on the 9000 RPH boot plate to the field density of l.7, stabilize and print 100 sheets, from 100 sample sheets Randomly extracted l0 for measurement analysis. 2 Print at a rate of 5000 RPH for 10 minutes. Take samples every 2 minutes for a total of 10 photographs. 3 Print at 1000 RPH for 10 minutes and take every 2 minutes for a total of 10 shots.

The samples taken out were measured with the DigiDens T6CR color reflection densitometer to measure the density and dot value of the corresponding field, and the relative contrast K value was calculated. When the K value was calculated, the average field density and the average density of 75% were used.

Second, the experimental analysis

1. Field density analysis

The solid color patch is actually a layer of ink film with a certain thickness, and the solid density is determined by the nature of the ink pigment and the attachment material to absorb light, as well as the thickness of the ink layer and the state of the ink conjunctiva. In the printing, once the type of ink is determined, the factors that affect the density of the ink in the field are the thickness of the ink film and the state of the conjunctiva. The print quality is controlled by controlling the thickness of the ink film. Measure the density value of the 40cm×1cm field test strip at the mouth of the proof, take a test point every 2cm, measure the mean value list of 10 proofs.