HP 1320 Service Manual - Page 87

Image-formation system Laser printing requires the interaction of several different technologies, including electronics, optics, and electrophotographics, to provide a printed page. Each process functions independently and must be coordinated with the other printer processes. Image formation consists of the following five processes: ● electrostatic latent-image formation ● developing ● transfer ● fusing ● drum cleaning The five processes contain eight steps, which are shown in Figure 5-7. Image-formation system and described in the following sections. Figure 5-7. Image-formation system Step 1: Primary charging Dc and ac biases are applied to the primary charging roller, which transfers a uniform negative potential to the photosensitive drum. Figure 5-8. ENWW Primary charging Step 2: Laser beam exposure The laser beam scans the photosensitive drum to neutralize negative charges on parts of the drum. An electrostatic latent image is formed on the drum where negative charges were neutralized. Image-formation system 75