What is the effect of printing speed on technical control and printing quality?

   The fluctuation of printing speed in the printing process is inevitable, especially from

the trial printing stage to the official printing, the printing speed often has a relatively

large increase. Changes in printing speed often cause changes in ink transfer, paper

positioning, etc. Offset press operators must be familiar with the various impacts that

may be caused by speed changes, and take corresponding technological measures to

maintain the stability of the printing process and printing quality . This article mainly

summarizes and discusses the influence of printing speed on printing quality,

and the corresponding process control measures that need to be taken. Effect of

printing speed on ink transfer rate

   The offset printing process is essentially the process of splitting and transferring

the ink layer between the blanket and the substrate. The ink transfer rate depends on

whether the split position of the ink layer is close to the paper or the blanket.

The closer the split position is to the blanket , the more ink transferred to the paper,

the higher the ink transfer rate.

   The splitting of the ink layer begins with the formation of a cavity inside the ink film,

and the cavity becomes larger and larger, gradually growing ink filaments, and the ink

is split into two parts here. The void is first formed on the side close to the paper,

and moves toward the blanket as it grows. The faster the printing speed, the shorter

the time the ink is in the imprinting area, and the void does not have enough time to

move toward the blanket. The separation position It is more inclined to be closer to

the paper. If the thickness of the ink layer between the paper and the blanket is constant,

the thickness of the ink layer transferred to the paper through separation will be thinner,

the ink transfer rate will be reduced, and the ink color will become lighter. This color change,

which is clearly discernible to the human eye for most dark prints, must be compensated

by appropriate measures. 

   There are generally two ways to make up for it: one is to increase the ink transfer rate

by increasing the printing pressure, but excessive printing pressure will increase the size of

the dots and the deformation of the substrate will be more serious, and after the pressure

reaches a certain level, increasing the pressure will not improve the ink transfer rate.

The ink transfer rate has little effect. Therefore, the color cannot be kept stable by simply

increasing the pressure; another method is to increase the thickness of the ink layer

reaching the blanket by increasing the corner angle of the intermittently rotating ink

fountain roller, and the distance between the blanket and the paper The thickness of

the ink film is thickened, so that when the ink transfer rate is reduced, the thickness of

the ink layer transferred to the paper remains stable, the stability of

the printed color is maintained.