In a printer assembly having a rack of ink-jet print cartridges, a backup cartridge is moved into alignment with a cartridge to be cleaned and the backup cartridge substitutes for printing of the cartridge being cleaned until the cleaned cartridge is moved back to its printing position. The backup cartridge is then moved into alignment with another cartridge and prints for that cartridge which is then cleaned. Ink-jet print cartridges must be periodically cleaned to wipe excess ink and particles from the nozzle array on the front face of the cartridge. Cartridges are cleaned by moving them to a cleaning station that wipes clean the front face of the cartridge. To avoid interruption of printing while cartridges are being cleaned, a backup cartridge is moved into alignment and substitute prints for a cartridge to be cleaned.