I'm looking at the print carriage ("X-axis") mechanism on my retired Canon Pixma MX340 multi-function inkjet, working to determine what that motor might do in addition to moving print cartridges (and their integrated print heads) back and forth across a sheet of paper. I've established it has linear encoder feedback for closed loop control over its entire range (32.5cm) of motion. I know the paper feed ("Y-axis") motor does a lot more than just feed paper, what else might the print carriage motor do?

One pulley for the print carriage toothed belt is mounted directly to motor output shaft, with no gearbox or other mechanisms, so it's not driving anything else on this end.

I had thought perhaps there would be a shaft for power transmission connected to the other belt pulley, but that search came up empty. The pulley is mounted on a sliding mount under spring tension so it could absorb mechanical shocks to the carriage system. There were no means to convey rotational power.

Looking for interactions beyond direct power transmission, I noticed a lever not far away.

It pokes through to the front, where it can be engaged by the print carriage.

Manually sliding the print carriage around, I found the lever is pushed by the print carriage when it is 2cm away from the right side edge. I won't know what this lever does until further disassembly, but based on its position, I expect it is a way for the print carriage (X-axis) motor to shift something in the gearbox turned by the paper feed (Y-axis) motor.

And now that I'm thinking about it... there's a chance the print carriage "parking brake" pawl does double duty. When the print carriage is in its rightmost parked position, the pawl can fully extend to keep the carriage in its parked position. When the carriage is slightly away from its parked position, the pawl hits the back of the carriage and could not fully extend. When the carriage is in the paper printing area, that pawl could fully extend again. When I take the gearbox apart, I'll have to keep my eyes open to see if it does anything clever with a partially extended pawl.

But that's not until later when I take apart that gearbox. More accessible right now is the print head ink maintenance assembly, which is also actuated by the print carriage.

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