I disassembled the control panel for this Canon Pixma MX340 multi-function inkjet and took a quick look from a mechanical perspective. I'll return later for an electronics examination but right now I wanted to dig into the rest of the scanning/copying automatic document feeder (ADF). I got a taste of what's involved in an ADF from a clever lid mechanism, now it's time to see the rest of it.

The control panel had to be disassembled first because it uncovered the fasteners and latches I needed to release before I could remove this back cover.

Then I could see the ADF motor and gearbox assembly, including the gear that drove the ADF lid paper feed rollers. Judging by the presence of four wires going into this motor, I believe this is a bipolar stepper motor.

Removing the bottom of the ADF paper feed tray allowed visibility into the core of this mechanism. In addition to paper handling rollers, I see a pair of photo interrupter sensors.

A plastic paddle attached to the bottom of the ADF paper feed tray slots into a sensor, visible towards the top of this picture. It detects when a document has been placed in the ADF. The sensor at the bottom of this picture still has its matching paddle in the slot, it detects whether a sheet of paper has been properly fed into the roller assembly.

Adjacent to the motor gearbox, I saw a beefy ground wire attached to foil tape.

This foil tape led into the middle of the ADF assembly...

... and out the bottom where it hovered over the entire width of the output tray. I believe this intends to dissipate any static electricity built up after the sheet of paper passes through the document scanner. The more interesting question is: was this always part of the design? Or was this added after testing uncovered problems with static electricity buildup? Foil tape is simple and effective for conducting low current, a good fit for managing static electricity buildup. But if static electric dissipation was the goal, I would have expected some stamped sheet metal integrated into this plastic structure. Foil tape felt like it might have been a hack. Which is fine, if it was. Canon engineers are only human after all and this machine already has more than enough intricate designs to facinate me.

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