New Gear Saves Old Printer

As the digital photographic revolution took off, and everyone bought a shiny new film-less camera, there was a brief fad for photo printers. The idea was you’d have the same prints you’d always had from film, but the media for these printers would invariably cost a fortune so consumers moved on pretty quickly.

Now the pop up in second-hand stores and the like, which is how [Amen] acquired a Canon Selphy 740. It didn’t work, and on investigation it was found that a particularly tiny plastic gear had failed. Most people would have tossed the printer in the trash, but they instead opted to CNC-machine a new gear. It’s not everyday you tackle a job this small, so it makes for an interesting tale.

While the first instinct might be to reach reach for a CAD package, [Amen] instead wrote a script to create the raw GCode. The machining is done with a 0.2 mm bit ground to the desired profile. The result: a gear that gets the printer working again. It’s a dye-sublimation printer that leaves a negative image in the cartridge, allowing negative prints to be made with a bit of cartridge rewinding. And for those who might have ended up with a Selphy of their own, there’s a further post about using cheaper aftermarket cartridges.

18 thoughts on “New Gear Saves Old Printer

  1. Oh man, it hurts that he plunged in and then translated along the part – that deflection could have been partially avoided if he just did that motion in reverse

    1. Yeah. You could tell that wasn’t done by a actual machinist. I was assuming it was sticking out so far because of turret clearance issues. Or he could of used a center. Lol

  2. I had a similar failure in a soft-ish plastic gear in a car speedometer. (Soft material was allegedly to reduce noise: it was a common failure in that car.) I reassembled the chunks as best I could and took the gear to a local clock repair shop. The helpful clock dude located and sold me a compatible brass gear. I never noticed any additional noise.

    1. A secondary reason for using a softer plastic component in a mechanism is to give it a controlled point of failure. Although I’m not sure which gear you had to replace, or the location, I’ve seen other speedos with a similar gear which was relatively easy to access (also was switchable in cases where diff/transmission rations where different). Much easier to deal with, vs pulling open the speedo and replacing components deep in the housing.

      I’ve also seen harbor freight lathes have a plastic gear, so when you crash the carriage into the chuck it’s relatively cheap to repair.

      1. It was accessible enough, but didn’t appear to be designed as an easily serviceable part, though that concept makes a lot of sense. Being an older car, the original part was unobtanium so had to find an alternative.

        Thanks for that insight.

        Is the HF plastic gear available as a repair part? Because if I had a lathe, I’d surely crash it a few times. Probably a good reason to start with a cheapie.

  3. Don’t show us the gear, show us how he ground a 0.2 mm ‘bit’.

    That’s the interesting thing here. Not some gear that could have been hand made on a lathe.
    You need an accurate spin fixture and a light touch to grind a cutter that small. 4 jaw chuck and a lathe, maybe, with much patience.

    It’s cutting plastic, so the end mill doesn’t have to be hard, but find a tiny mild steal end mill.

    1. I’m not sure about the bit geometry, but it could be something like this:

      I have made similar bits out of broken carbide endmills with just Dremel and a diamond wheel. First grind the outer cone, then grind a flat to midway. Finally sharpen with a flat diamond sharpener.

      They are not particularly good cutters because the geometry is very simplistic, but work ok in plastic.

      1. Beware carbide dust!

        It will kill you if you suck enough of it up. It will kill about 1 in 50 (who are particularly reactive) with very small exposure. No way to tell if you’re one of the lucky ones, so the standard is to assume everybody is.

        Read the MSDS on grinding carbide. It’s largely the cobalt the binds the carbide grains together, there is nothing good about it. Awful, slow way to go.

    2. It was a ‘D’ bit tat I’d broken the tip off on another project. I ground the end to match the gear I had. As the scrap material I used was soft the profile of the gear wasn’t critical. This wasn’t a high precision machining job.

      1. Thanks for the reply.

        Just from curiosity, are you aware of the ‘standard’ way to cut a gear in a lathe?
        Special tool holder (90 degrees off) pushed lengthwise through the material, while holding the chuck (and after marking clock lines on it).

        You can get carbide cutters in standard gear profiles. Easy to do with soft metals.

  4. I have seen a few of these show up in the used or secondhand stores now and they are fairly impressive little printers!
    So far all of the cartridges seem to be interchangeable between the different generations and I picked up the same generation as the author last year to start printing with.

    The print quality for the cost of materials is quite good; better than some discount photo printing services and so far much more resilient than high-end inkjet printing.

    I have been watching the 3rd party products and am interested to try them out.

  5. Some older Canon Pixma portable inkjet printers (specifically the ip90 and other models using the same core parts) have a badly designed tiny gear in the paper feed that has a 100% failure rate. It *will* split in half due to it having a metal core and plastic outside. The plastic shrinks a little as it ages and when that comes up against the metal, the plastic splits. Gluing it doesn’t work because the geartrain is very high precision and the inevitable slight tooth variance will make it jam.

    Canon made an improved gear that’s all plastic so when it shrinks a little it *all* shrinks, which has the nice property of making the center hole self compensating for wear. Getting the printer opened up and apart to be able to replace the gear is a big PITA, but knowing that it’s not going to fail again is a good feeling after the job is done.

    The other problem of that printer series is the metal “bridge” across the paper path, under the top plastic, can easily get bent downward if heavy objects get piled on it or it’s packed into a laptop bag where it can get bumped or something presses against it. Then paper won’t feed through. Fortunately that is fixable with some very careful prying with a large, flat screwdriver.

    They are pretty nice printers, Windows 8 drivers (which also work with 10), in English, can be found on Canon’s Asian site. For some reason Canon doesn’t want the EU and USA to use an ip90 or its family members with Windows 8 or 10.

    So should you come across one of these being sold as working, make sure to ask if the paper feed gear has been replaced with the improved version. I got one for free because it didn’t work. Came with two new ink cartridges. Paid $15 for a new gear, spent about 45 minutes replacing the gear, did the prying to fix the bent ‘bridge’, sold it for $50, with the Win 8 drivers burned on a CD-R. IIRC I also sold the same guy a used laptop I had very little $ into fixing and upgrading.

  6. On the subject of printers, I have a Canon 1700 here which is now obsolete because WIndows 10 does not support it.
    Any ideas please?
    Very fortunately have a somewhat newer printer which does run.
    As it happens you can’t get the cartridges, but have a plan if it isn’t possible to make it run.
    Namely reprogram the IC so it can use different cartridges.

    1. “Canon will not issue drivers for this model to support the Windows 10 operating system. The Windows 7 drivers should function in the Windows 10 environment with some limitations which are currently unknown to Canon.”

    2. You may be able to run it with generic canon drivers. I’ve got a couple of ancient (~20 year old) HP printers that are still running fine on latest OSX and on Win10 using generic HP drivers.

      I’ve got a canon inkjet maybe ~5 years old which I can’t install the official drivers for that printer, but newer non-printer-specific canon drivers provide all the core functionality on OSX (mainly just lost the pretty config screens!)

      I’ve not got Win11 yet so YMMV.

  7. The “cool,” but otherwise stupid motorized 3.5″ floppy ejection mechanism on Apple computers has the same and common problem. Resin 3D printed replacements are available.

    1. Hmmm are the smaller/cheaper SLA printers high enough res to justify having one for jobs like that?

      All this while I’ve been deferring purchase for a “do it all” printer, and now I think I need a small precision SLA, a “normal” FDM and a chunky monkey delta.

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