Replacing the developer without completely removing old developer causes the machine to operate in a condition in which the applied toner density value is lower than the actual value. This happens because the toner density sensor (TD sensor) initialization process (SP3-030-001 to 006), which is performed when replacing the developer, always sets back the toner density readings to the prescribed standard value 7.0% regardless of the actual toner density, e.g. actual toner density could be 8% after replacing with fresh developer but the TD sensor is calibrated to read this as 7%.
Continuous machine operation in this condition and incomplete developer replacement will eventually cause the actual toner density to become too high and result in toner scattering.
This procedure explains how to remove old developer to prevent toner scattering, in two parts.
Following are the expected effects:
Easier developer removal as a result of improved developer fluidity
Toner density will come close to the standard 7% after developer replacement even if the dev unit is not completely cleared and contains a slight amount of old developer.