Oki B6200 Maintenance Manual page 608

In the cleaning step, the remaining toner is removed from the drum surface. The drum surface is
prepared for the next cycle.
The toner is scraped off the drum surface by a cleaning blade.
The toner scraped off in the cleaning step is collected in a recovery toner compart-
ment partitioned from unused toner. The transfer rate is normally more than 90%,
but varies according to the image coverage range and environmental conditions
such as temperature and humidity. The used toner cannot be reused.
When the printing step is started, the whole drum surface is scanned with a laser
beam. If charges generated in the previous step remain on the drum surface, they
are completely removed. When the continuous printing step is started and finished,
a negative high voltage is applied to the BTR. If toner particles adhere to the BTR in
the previous printing step, the toner particles are returned to the drum surface. In
this way, the surface of the BTR is cleaned.
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Chapter 6 Principle of Operation