Changing the ink ribbon in a Canon MP27D can be a tricky process if you're not familiar with the machine. Incorrect installation can cause smearing, jamming, print failure and ink leaks on the calculator's components. Luckily, you can avoid these installation issues--as well as staining your fingers with ink--by following a few simple steps.
Remove the printer cover, which rests where the paper comes out on the top of the calculator, by sliding the cover away from the back of the calculator. Place it aside.
Remove the used ribbon by pulling each of the two spools directly upward at the same approximate speed. Avoid unravelling the used ribbon or touching the inked fabric inside.
Open the new ribbon and place one of the spools onto the spool pin on the left-hand side of the calculator. Press gently until you feel the spool "click" into place.
Hold the second spool in your hand. Guide the new ribbon carefully through the printer ribbon guides, being careful not to touch the fabric. Seat the second spool on the spool pin on the right-hand side of the calculator. The ribbon should now have a "U" shape, with the ribbon passing around the outer side of each spool.
Return the outer print cover to its original position. Do a test calculation to ensure that you've correctly seated the spools and threaded the ribbon. The ink on the printed calculation should be crisp and clean, and there should not be any smudges or jamming in the printer.
Your Canon MP27D calculator can use a wide range of manufacturer's ribbons beyond those sold by Canon. Most brands indicate on their packaging which calculator models each of their ribbons are compatible with. "Off brand" ribbons are often cheaper than Canon ribbons, and they perform just as well.