Seiko Instruments SII Black-and-White Raster Plotter LP-1020 - Manual (Page 254)

14-38
When there is an abnormal sound
If you hear an abnormal sound, contact your dealer or our service center.
Note
◆ In order to prevent the waste toner from accumulating
unevenly in the waste toner bottle, this device provides
the maintenance function that taps the waste toner bottle
at the definite interval to level the waste toner. (⇒ page
14-36)
Taps will be heard during the maintenance of waste
toner, but this is not a problem.