How to Change Ink Cartridges on a Canon MP450

1. Grab the scanning unit that makes up the top lid of the printer on both sides, toward the front of the printer. Lift the scanning unit, pivoting it on the hinge at the rear of the printer.
2. Pull the small plastic scanning unit support lever located beneath the right-hand side of the scanner unit down as you lift the unit. Prop the lower end of the lever into the small notch on the top of the right ledge of the printer cavity, in order to hold the scanner unit above the cavity to access the cartridges. The cartridge caddy within the printer will move to the left-hand side of the printer cavity as you open the scanner unit so you can access the cartridges.
3. Remove the empty print cartridge by pulling the cartridge directly back from the cartridge caddy until it stops. Place your thumb onto the small half-circle ridge on the top of the cartridge and tilt it downward and to the rear to disengage it from the cartridge caddy. Lift the cartridge free of the caddy.
4. Remove the protective tape from the side and bottom of the new cartridge. Be careful not to touch the print circuitry revealed with the tape removal. Use the CL-51 color cartridge if replacing the color ink, and the PG-50 black cartridge for black ink.
5. Insert the new cartridge into the cartridge caddy. Tilt the new cartridge into place with the larger end of the cartridge containing the print circuitry higher than the other end and toward the rear of the printer. Lift the lower end of the cartridge upward, easing the circuitry end into the caddy until the cartridge is level. Push the cartridge forward into the caddy.
6. Lift the plastic scanning unit support lever and lower the scanning unit. When closed, the cartridge caddy will move to the right of the printer cavity and make several passes across the printer to prepare for printing. Wait about two minutes for the printer to complete the passes before printing.