HP Indigo colordigital printing machineIt is a typical representative of electrophotographic digital printing technology using liquid coloring agents. The HP Indigo system will be used as an example to introduce such systems.
Figure 2-13 shows the basic structure of the HP Indigo digital printing press, including the operating platform, imaging laser, plate cylinder (photoconductor drum), developing roller, blanket cylinder, impression cylinder, input tray, output tray , Double-sided printing input tray and ink cartridges of various colors.
Figure 2-14 shows the working process of HP Indigo digital printing machine:
(1)Static electricity is loaded on the photo image plate (Photo Image Plate) of the picture drum, so that its surface is filled with the same kind of electrostatic charge.
(2)The photoconductive drum is exposed through the scanning array of laser diodes. The laser is controlled by RIP (raster image processor), which converts digital files into commands to control the laser switch. When the photoconductor drum rotates through the imaging unit, more than 12 imaging laser beams expose the photoconductor drum, and the exposed graphic area discharges. After exposure, a graphic latent composed of invisible electrostatic charges was formed on the surface of the photoconductor drum.
(3)Ink, and clear the ink in the blank area through the high-voltage developing roller. In the digital printing machine, the ink is drawn into the area between the photoconductor drum and the developing cylinder through a hose, and the ink is evenly injected along the cylinder gap through an accurate control mechanism to fill the gap between the cylinders. Since the developing roller and the photoconductor drum have different voltages, a strong electrostatic force is generated between the two rotating rollers. This force attracts the charged ink particles to the discharged graphic area, while the charged blank area does not absorb the ink particles. The ink repelled in the blank area is transferred with the developing roller and recovered into the ink tank.
(4)Remove excess liquid and ink particles in the blank area on the surface of the photoconductor drum, and remove loosely adhered ink particles in the graphic area. As the photoconductor drum rotates through the water roller, this part of the water roller includes two very small charging rollers (water roller and reverse roller), which are opposite to the direction of rotation of the photoconductor drum. The reverse roller is installed close to the photoconductor drum, and most of the liquid and ink particles remaining on the photoconductor drum are removed from the blank area by the force of electrostatic attraction and water pressure.
