I'm close to the end of tearing down my Canon Pixma MX340 multi-function inkjet. After the paper feed motor was freed from the plastic base, there's not much more I could do to that assembly because I wanted to keep the motor and encoder together. So I turned my attention to the print carriage assembly, with its own encoder I have yet to access.

Earlier disassembly saw fasteners I couldn't access from the front. I will now take apart the print carriage rail in order to free the carriage itself and allow access to those fasteners.

Looking at the assembly I saw the backbone sheet metal was folded up top to form the upper rail, and there were folds left and right to keep the carriage constrained. The only thing that could move is the lower rail, which is a separate piece of sheet metal. (In above picture, the lower rail is visibly covered with darkened lubrication grease.)

At this point I noticed the lower rail is mounted slightly tilted from the bottom of the backbone. I measured it was raised by 2.07mm on the left but only 1.41mm on the right. This slight tilt was probably part of factory calibration to ensure the print head travels exactly parallel to the paper surface at all times.

Before releasing the lower rail, I unhooked the encoder strip's tension spring on the left.

The drive belt was also unhooked from the right side tension pulley.

An vertical alignment reference marker is visible to the left of this lower rail screw.

Removing the screw made it clear there's allowance for a few millimeters of lower rail adjustment.

By removing the lower rail, I have destroyed its precision factory alignment. But with the rest of the printer taken apart I doubt it matters anymore. I'll ignore that and keep digging.

This teardown ran far longer than I originally thought it would. Click here to rewind back to where this adventure started.