HP LaserJet 4 Service Manual - Page 128

Image Formation System Laser printing requires the interaction of several different technologies (such as electronics, optics, and electro-photographics) to provide a printed page. Each process functions independently and must be coordinated with all other printer processes. The image formation process centers around the photosensitive drum and consists of six stages: 1. Cleaning 2. Conditioning 3. Writing 4. Developing 5. Transferring 6. Fusing The toner cartridge houses the cleaning, conditioning, and developing stages of the electro-photographic (EP) process. Components of the image formation system that wear, degrade, or are consumed are built into the replaceable cartridge. The toner cartridge contains the photosensitive drum, primary charging roller, developing station, toner cavity, and cleaning station. This eliminates the need for a service call when replacement is required. Figure 5-6 Image Formation System 5-16 Functional Overview