Analysis and diagnosis of printing quality problem

Analysis and diagnosis of laser printer print quality problems (Part 2)

9. There are longitudinal white bars on the print

(1) the photosensitive drum

the photosensitive drum is damaged, and serious scratches are generated in the surrounding direction. The white part cannot be printed with any toner, resulting in longitudinal white bars

(2) charging part

1) if the charging electrode wire is stained with toner or other things, the corresponding part of the photosensitive drum cannot be charged, and white bars appear

2) the power supply voltage drops, resulting in uneven charging voltage, resulting in white bars with different widths and unclear edges. A

voltage stabilizing device can be added

(3) the developing part

has less toner and is uneven. You can add powder or change the drum

(4) the separation part

the separation claw is deformed and should be replaced

10. Regular or irregular white spots appear on the black image of the printing product

(1) the photosensitive drum

the photosensitive drum itself has defects, such as the photosensitive layer peeling off and the number of scratches and twists is 20000; Damage to other connections, etc

(2) development part

1) development bias voltage is too high, and white spots can also appear

2) toner contains impurities, which generally appear after powder filling

(3) charging part

1) low transfer efficiency produces small white spots, and the transfer telegraph wire should be adjusted and cleaned

2) the charging voltage is too high, and the photosensitive drum is ignited, punctured or semi punctured during discharge, resulting in fine white spots

(4) if it is a large white spot, it may be the result of local moisture on the paper and poor transfer

11. The image center of the print is white

the reason is:

1) the charging power is insufficient, and the charging corona electrode and other parts should be repaired

2) poor transfer, repair the transfer electrode and other parts

3) due to edge effect, it should be adjusted to clean the optical system and some mechanical parts

12. Black spots appear randomly on the printed matter

if the laser beam is randomly lit and disconnected, random black spots will be printed. This may be caused by printer control circuit failure, but sometimes it may also be caused by host failure. Self test printing can be used to determine the fault source

(1) regularly appear in a certain part of the print

if the stain is regular, the causes are the following

1) the surface of the photosensitive drum is scratched or contaminated

2) the solidified toner block is stained on the developing roller, so that the adhesion ability is strengthened.

3) the cleaning scraper of the photosensitive drum is damaged

4) transfer electrode wire charging corona electrode is uneven on the left and right, resulting in different depth on the left and right

5) there are scratches on the fusing roller, or the rubber on the surface of the fusing roller is aged

6) the cleaner of the fusing roller is defective

7) the thermistor in the fuser is damaged, etc

(2) appear irregularly on the print

if the stains on the print appear irregularly, it is because the paper take up wheel is polluted by toner, which is caused by the development of industrial technology

14. some imprints appear repeatedly on the printed matter

when a piece of paper passes through the printer, the 12 kinds of rollers in the machine turn more than one turn. The largest photosensitive drum rotates 2-3 times, and the paper feeding roller can rotate more than 10 times. When marks with equal intervals appear on the paper, it may be caused by dirty or damaged binding rollers. Suppose there is a stain on a roll. When it rotates, every time the stain contacts the paper, it will leave a mark

if the marks are close, they may be formed by small rollers. If they are far away, check the larger rollers

measure the distance between the imprints, and then calculate the roller diameter of the guide imprint with the following formula:

roller diameter = imprint distance/3.1416

for HP series printers, the diameter of the photosensitive drum is about 91mm (3.75 inches basically become an inch of China's living map), the developing roller is 51mm (2 inches), and the fixing roller root is 76mm (3 inches). If the roll diameter is 91mm (3.75 inches) according to the imprinting distance, the photosensitive drum should be checked first

15. The reason why the left or right side of the printing paper turns black

is that the laser beam is scanned outside the normal range, the position of the reflector above the photosensitive drum changes, the toner box fails, and the toner in the box is concentrated on one side of the box, which may cause this kind of failure

remove the toner box and shake it gently to make the toner in the box evenly distributed. If it is still not improved, replace it with a new box

16. Pollution on the back of the printing paper

the reason is:

1) the toner in the developer or cleaner is sprinkled on the paper conveying path, causing pollution on the back of the printing paper

2) the fusing roller is not clean, and the toner is stained on the lower fusing roller, which pollutes the back of the paper

17. the image on the print is easy to be erased

the image on the print is easy to be erased, which is mainly due to insufficient fusing. The fault lies in the following two parts:

(1) fusing part

1) fusing lamp tube is damaged or in poor contact; The heating wire is broken, causing no fusing temperature or too low fusing temperature, which should be repaired or replaced

2) the fusing heating roller is worn, there are pits on the surface, the contact with the paper is not close, and the local fusing is not firm, so it should be replaced

(2) developing part: toner inconsistent with the model of this machine is used, which is difficult to meet the requirements of its fixing time, so the manufacturer does not advocate filling toner

18. excessive fixing

when laser fixing is excessive, the lines of the printed image will become thicker, the resolution will decline, and the paper will turn yellow and brittle

the reasons are as follows:

1) the radiator or cooling fan is damaged, causing the temperature in the printer to rise

2) the thermistor is too far away from the fusing roller and is insensitive to the temperature rise in the machine

3) the control circuit fails, causing the fusing temperature to be too high

4) the power supply voltage fluctuates greatly, which affects the fixing effect

5) 50% of the paper is polyamide Ultramid b3eg10 Si (Si = surface improvement) filled with glass fiber, which is too thin to withstand the high temperature of the fuser