HP 4600 Service Manual - Page 156
Developer rotations, Toner sensor, Photosensitive drum rotations, Toner-level, detection
UPC - 808736060875
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Developer rotations The developer-roller rotations are tracked on the print cartridge memory tag (e-label). Tracking rotations enables the printer to signal that a print cartridge is low or out before the developer or toner is actually worn out, which would result in print-quality defects. Over time, the toner loses its required properties as a result of excessive stirring and recharging. Although the cartridge will correctly signal LOW or OUT because of wear, some toner might remain in the fresh-toner hopper. In addition to toner wear, the developer roller wears during use, so developer-life tracking is necessary. In situations where low-coverage documents are printed frequently, the developer rotations might cause a LOW signal before the toner level reaches its low level. Toner sensor For the first 75% of the cartridge life, toner depletion within the cartridge is calculated by counting pixels. An optical toner-level sensor then tracks the final 25% of toner. The toner is measured and then reported on the toner gas gauge on the control panel or on the supplies status page. The transition from counting pixels to optical toner-level sensing causes no fluctuations on the toner gauge. Some toner might remain in the fresh-toner hopper although other cartridge components have reached their end of life. Photosensitive drum rotations Photosensitive drum rotations are also tracked on the cartridge memory tag. Similar to the process for the developer roller, tracking these rotations enables the printer to signal that a print cartridge is low or out before the photosensitive drum is actually worn out, when print quality defects would occur. Wear on the photosensitive drum might cause a low message when low-coverage documents are printed frequently. Tracking of drum life is essential because of drum wear and the potential for overflow from the waste-toner hopper if use of the photosensitive drum is overextended. Figure 5-17 Toner-level detection illustrates the toner-level detection system. Figure 5-17 Toner-level detection 140 Chapter 5 Theory of operation ENWW