1. The scraper of the magnetic roller of the printer is aging;
2. The distance between the developing magnetic roller of the printer and the photosensitive drum is too close, such as the gap wheel or gap shaft sleeve on both sides of the magnetic roller is damaged;
3. The photosensitive drum of the printer is excessively worn and has reached the service life;
4. The toner of the toner cartridge is too slag;
Second, the general maintenance method:
1. First, open the cover and adjust the print density knob to the middle position (some models need to use printer driver settings to adjust) to see if the bottom ash phenomenon has improved. If there is any change, it means that the magnetic roller bias is too low.
Under normal circumstances, as long as the printing density is within the adjustment range, there should be no bottom ash phenomenon.
Clean the magnetic roller contact to ensure good contact. Then use a multimeter to measure the development bias, which should generally be between -250V and-350 V. Different models have different bias values. If the deviation is too large, it should be repaired or adjusted to the specified value.
2. Check the magnetic roller scraper.
Take out the toner cartridge assembly and rotate the moving photosensitive drum in the paper feed direction. If toner sticks to the surface of the photosensitive drum, it may be that the magnetic roller scraper is aging and deformed, which cannot limit the supply of toner, so the magnetic roller scraper should be replaced.
3. Excluding the above two situations may be caused by the close distance between the developing magnetic roller and the photosensitive drum. In general printers, there should be a certain gap between the photosensitive drum and the magnetic roller to facilitate the toner jumping. Most models maintain the gap by installing spacers at both ends of the magnetic roller. The thickness of the isolation sleeve is the standard gap. Different models have different gaps, generally between 0.2 and 0.4 mm, which will wear the gasket during printing and reduce the gap. Sometimes during maintenance, the isolation sleeve is lost, resulting in no gap.
None of the above is true, so it can be concluded that the photosensitive drum is excessively worn and has reached its service life. How to judge excessive wear of photosensitive drum? This situation is unlikely to happen in printers that use brushes to clean. For printers with scraper cleaning, you can observe the printed test samples. If bottom ash appears in the range of 1cm between the left and right sides of the longitudinal paper feed and the paper edge, it means that the photosensitive drum has been excessively worn and cannot be repaired, so the photosensitive drum can only be replaced.