Cause
When drastic environmental changes or prolonged disuse occurs after stopping the machine, moisture is absorbed only to areas contacting the development unit and drum cleaning unit on drum. This makes uniform charging of the drum impossible and causes uneven density.
This is likely to occur if:
Printing a halftone image
Drastic environmental change from the HH condition (high temperature and high humidity) to the LL condition (low temperature and low humidity)
The machine is not used for 30 minutes or more after the machine operation in the low temperature and low humidity condition.
