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Disappointing Canon Pixma teardown.

Started by Sylvia Else May 13, 2017
I bought this printer and scanner combo to print circuit board masks, 
but it doesn't do a very good job. I've acquired an Epson printer that 
works better. Since the Canon printer has has next to no value on the 
second hand market, and would just be occupying space, I thought I'd 
pull it apart and see what could be salvaged.

I did get a nice 24V 0.65A PSU, which may come in useful one day, but 
not the few stepping motors I'd been expecting. Instead it uses simple 
DC motors with optical position sensors. Since when I was looking at 
buying some optical position sensors, they cost and arm and a leg, this 
rather surprised me.

As implemented in the Pixma, the optical sensors are quite delicate. I'd 
have thought they'd also be susceptible to dust.

Sylvia.

On 5/12/2017 9:45 PM, Sylvia Else wrote:
> I bought this printer and scanner combo to print circuit board masks, but it > doesn't do a very good job. I've acquired an Epson printer that works better. > Since the Canon printer has has next to no value on the second hand market, and > would just be occupying space, I thought I'd pull it apart and see what could > be salvaged.
Most modern printers have very little salvage/recycle value. Far too many plastic parts (plastic has no value). I routinely encounter large format (e.g., 16-36") inkjets that no one has ANY interest in rescuing. [I've got a DesignJet 755CM that I use for 1:1 templates of oversized items: <https://www.cnet.com/products/hp-designjet-755cm-series/> But, ink costs are outrageous so it sees little use. And, its not as entertaining to watch as the pen plotter was -- though it's not limited to line drawings as was the case for the pen plotter!]
> I did get a nice 24V 0.65A PSU, which may come in useful one day, but not the > few stepping motors I'd been expecting. Instead it uses simple DC motors with > optical position sensors. Since when I was looking at buying some optical > position sensors, they cost and arm and a leg, this rather surprised me. > > As implemented in the Pixma, the optical sensors are quite delicate. I'd have > thought they'd also be susceptible to dust.
Its possible (and common) to effectively operate stepper motors as DC servos and vice verse. Most modern printers are not "character at a time" -- where the carriage walks across the page incrementally, typing out each "character" as it is received (like a TTY would). Instead, they buffer a line (or page!) worth of data and reproduce it as effectively as possible. In your case, they send the carriage across the page and use the position of the carriage (print head) to determine what to print -- and *when*. In theory, decoupling the drive of the motor from the actuation of the printhead. Of course, there are constraints applied to the motor drive and/or compensations that are applied to the printhead actuator to optimize the performance of the "system". E.g., as the motor speed increases, the printhead needs to be fired slightly earlier to account for the physics involved (ink moving through the air). A firm I worked with manufactured a printer that was stepper motor driven (carriage and platen). But, the software was designed to treat the motors as DC servos; we'd use back-EMF from the stepper motors to determine when a step had mechanically been completed (instead of an encoder) and use that to dynamically adjust the acceleration profiles (want to get the motors moving as fast as possible as quickly as possible). If the system ever lost track of the carriage motor's armature's position, the carriage would be "homed" at a safe, open-loop rate until it knew it was at the left margin; then the process resumed (knowing NOT to start printing until it had reached the point at which it had last "made a mark") [Of course, you don't want to screw up like this, often, because it drives your performance way down!]