Canon BJC-55 User Manual page 34

Using a USB Connection
Wait at least five seconds before disconnecting the USB interface cable.
If you must disconnect the USB interface cable, wait at least five seconds after turning off
the computer and printer. Removing the cable immediately after turning on the computer or
printer could cause problems with the printer.
If you have more than one printer connected via USB, use an externally connected
USB hub.
Disconnect printer or hub first
If you must disconnect the USB interface cable with the computer's power on, always
disconnect the USB interface cable from the printer or USB hub before you disconnect it
from the computer.
Getting Ready to Print 34