I know I haven't uncovered all of the paper handling mechanisms of this Canon Pixma MX340 I'm taking apart, but I'm already impressed with the partial overview I've got so far. Right now my focus is tracing those paper feed rollers back to the motor gearbox driving them.

There are two paper feed rollers visible here, one before and one after the printing area. Each of those roller shafts are attached to a large white gear. A smaller intermediate gear sits between them to drive both. Earlier I had thought the motor must be behind that center gear, but it turned out the motor was actually a little lower.

The motor output shaft has a small black plastic gear, almost blending into the shadows. I traced only two wires leading into this area, implying it's a brushed DC motor down there. Some of the older inkjet printers I took apart earlier used stepper motors for open-loop control. In this printer, precise control is accomplished with a closed-loop control system: the gear on the left has an encoder wheel and a sensor reading its motion providing feedback.

Flipping my camera lens to "super macro" mode, I got this close-up picture of the encoder ring. It is series of very fine evenly spaced radial lines, consistent with an incremental encoder. I see four wires leading to the sensor, consistent with things I expect to see: power, ground, A, and B. I'll hook them up to my oscilloscope later to verify this deduction.

This motor drives a lot more than the two paper feed rollers immediately adjacent to the print area. One of the paper feed rollers transmit its power all the way across the printer to a gearbox behind the print head parking area. It's likely involved in feeding paper from the input tray, and others I look forward to deciphering later. Right now, though, another interesting feature of this printer is immediately adjacent and accessible.

This teardown ran far longer than I originally thought it would. Click here for the starting point.