Inside my old retired Canon Pixma MX340 multi-function inkjet is a gearbox that choreograph a sequence of motions to feed a single sheet of paper from a stack in the paper tray. I want to see that mechanical wizardry firsthand so I removed the screws holding the paper tray assembly to the base. Once freed, I lifted the assembly and the movement felt like I was peeling something sticky. That was unexpected... what happened?

I had found the hidden ink graveyard underneath, and an explanation for the tubes that caught my interest earlier. A thick layer of absorbent material has been installed across the base of this machine. Ink jetted in the parking position during priming or other maintenance tasks are pumped through those tubes and deposited into this diaper. The sticky sensation I felt came from semi solid globs of ink sticking to the bottom of the white plastic assembly.

My cheapskate brain can't help but think "There must be over $100 worth of ink here, wasted!" I understand it's not realistic to expect 100% of ink to end on a page, and some consumption for maintenance is unavoidable. But when ink cartridges are the profit center, it's easy to be suspicious if all of this was actually necessary because they certainly have a perverse financial incentive to be wasteful.

There were two distinct ink disposal areas. A smaller one for the color ink cartridge, and a larger thicker one for black ink. I've used up a larger fraction of color ink absorption capacity due to my usage pattern: I have a black-and-white laser printer so I only used this inkjet when I needed color. Usually photo printing. Thankfully I was nowhere close to maximum capacity. It would have been a very messy discovery! Absorption capacity limit is why even "high volume" inkjet printers fed from bottles of ink have a finite service period before they require their diapers to be changed. I wonder if this MX340 has its own "stop using me" countdown for the same concern.

Now that I see the final destination for ink that would never end up on a page, I could trace the path taken by the ink disposal system.

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