Common Issues with Charging Rollers and Their Impact on Printing Quality
Author:Ruiming Office Addtime:2025-11-28 11:31:13 Click:8
Essentially, all problems with charging rollers can be attributed to two causes: failure to uniformly charge the surface of the photosensitive drum, or contamination of the photosensitive drum during the charging process.
This is the most common issue. Foreign substances such as toner, dust, and paper scraps can adhere to the soft surface of the charging roller.
Vertical black thin lines and streaks: This is the most typical symptom. When there is a stubborn stain on the charging roller, it repeatedly creates a point on the same rotational position of the photosensitive drum that cannot be charged normally. This point absorbs a large amount of toner during development, resulting in a vertical black thin line running from top to bottom on the printed paper.
Repeating stains/marks: If the contaminant is small and fixed, it will cause an error point on the photosensitive drum at intervals equal to the circumference of the charging roller as the roller rotates. Eventually, this leads to repeating stains or small black spots with equal horizontal spacing on the paper.
The surface of the charging roller is coated with a special conductive rubber/foam layer. Long-term friction with the photosensitive drum and exposure to high-voltage electric fields can cause this layer to age.
Large-area background graying: This is the primary symptom of aging and abrasion. When the surface of the charging roller becomes uneven due to wear, or its conductivity decreases in some areas due to hardening, it can no longer provide a uniform, high-potential surface charge to the photosensitive drum. Areas on the photosensitive drum that are not fully charged will absorb some background toner that should not be adsorbed during development, resulting in overall graying of the entire page and a "dirty black background." The printed result will appear dirty with reduced contrast.
Blurred edges of text/images: Uneven charging leads to unclear edges of the electrostatic latent image. This causes the lines of the finally printed text or images to be less sharp and the edges to appear fuzzy.
This is caused by the entry of foreign objects or improper cleaning (e.g., scraping with sharp objects).
Thick vertical black or white lines:
If there is a deep scratch, the scratched area will create a thick vertical line with clear edges, similar to the "contamination" issue mentioned above (usually black).
If the scratch is extremely thin and runs through the entire roller, it may form a vertical white line where no toner is adsorbed (though black lines are more common).
Localized extreme instability in print quality: The conductivity of the scratched area is completely different from that of the normal area, leading to total loss of control over imaging in that region.
If the charging roller is not correctly installed in the drum unit, or its fixing springs/clips are aged and ineffective, it cannot maintain stable and uniform contact with the photosensitive drum.
Dark edges on one or both sides: If one end of the charging roller fails to contact the photosensitive drum, that side of the drum cannot be charged normally. During printing, dark vertical edges will appear on one or both sides of the paper.
Periodic uneven density: Unstable contact pressure may cause the charging level of the photosensitive drum to fluctuate as it rotates once, resulting in stripes of varying lightness and darkness in the vertical direction of the printed image.
The charging roller itself requires power supply from a high-voltage source. Although the problem originates from the power supply, it manifests as a charging roller fault because the issue directly acts on the roller.
All-white/no image: If the high voltage fails completely, the charging roller cannot charge the photosensitive drum at all. In this case, no matter how the laser "writes," an electrostatic latent image with charge differences cannot be formed, and toner will not be adsorbed—resulting in a blank printed page. This is usually caused by a fault in the printer’s high-voltage board or related circuits.
Entire page all black: Contrary to the above situation, this is usually caused by a high-voltage short circuit. The surface of the photosensitive drum is filled with incorrect charges, causing its entire surface to absorb toner, resulting in a fully black printed page. This is a dangerous fault; the printer should be turned off immediately for inspection to avoid damaging other components.
Severe snowy/wrinkled images: Unstable high voltage, filled with noise and interference, leads to extremely uneven charging, resulting in disorganized and messy images.
Konica Minolta C258 DR313 drum units Primary Charging Roller
