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  1. #1

    Which one looks better?

    So I'm working on a project which involves gears, and I've got the option of two types of chamfers I can put on. They both serve the purpose I'm intending, but aesthetically they look quite different. Usually I don't fuss about aesthetics but since these are functionally (as far as I'm concerned) identical, I figured it might as well be pretty too.

    One option ("Straight cut chamfer") cuts a uniform chamfer along the gear, I find myself partial to this one due to how simple it looks, but it requires a larger chamfer to cover the whole gear tooth, which cuts into the teeth quite a bit and you effectively end up with a narrower gear.

    Then I can also cut a chamfer which works more by following the tooth profile ("Profile following chamfer"). This lets me use a smaller chamfer but still get the entire gear tooth, effectively giving me a wider gear. I can do this in two ways, "vertical" or "slanted" where the chamfered part of the gear goes straight vertically, or where the chamfer is slanted along with the helix of the gear.

    My question to you guys, is which one looks best? Again, they all fulfill the same function so that isn't a concern. I think I like the straight cut chamfer best, but it eats up a lot of the width of the gear. I just think putting a "proper" profile following chamfer on something that's slanted looks kinda weird.

    Ignore the large number of facets, needed a quick openSCAD render to illustrate the different types. I can set the resolution much higher I just didn't want to wait forever.

    Check out the files on thingiverse (couldn't upload stls on here for some reason), and ignore the part where the gear teeth stop, that will be cleaned up on both of them later.

    https://www.thingiverse.com/thing:2549482

  2. #2
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    That doesn't look like any gear I've ever seen. What is it supposed to do? How does it work? Does it mount to a shaft or anything? Both pictures look weird to me; it's hard to say which is weirder.

  3. #3
    The tooth profile is cycloidal rather than involute which you're probably used to, which is why they would look weird. Cycloidal gears have a rolling point of contact rather than the sliding point of contact involutes have. This reduces friction and wear which is my primary concern in this application. Their downsides include a non constant pressure angle, which means you get non constant power transmission. Since I'm only using these gears to locate and register two mating parts, and not to transfer power, this downside isn't an issue.

    They don't mount to a motor shaft or anything, they are mounted to two limbs and are used to register the arms against each other. The gears are used to make sure the two arms they're attached to move symmetrically and are fully constrained, not transfer motion. Have a look for the GUS simpson 3d printer and you'll see how they're used. If you used smooth cams, the cams could slide along each other and the motion would not be properly constrained.

    Anyways, I wasn't asking for how weird the gears looked to you, I could have given you the same examples with an involute profile so they look 'normal'. I was asking about which type of chamfer you thought looked best aesthetically.

  4. #4
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    What difference does it make? Shouldn't you be more concerned with how well it works?

  5. #5
    Quote Originally Posted by Trakyan View Post
    Anyways, I wasn't asking for how weird the gears looked to you, I could have given you the same examples with an involute profile so they look 'normal'. I was asking about which type of chamfer you thought looked best aesthetically.
    The second one looks prettier. Just make sure they really have same advantages for your project

  6. #6
    Like I said, they serve the exact same function. That is to negate any effects over squashed first layers may have on the gears meshing.

  7. #7
    Super Moderator curious aardvark's Avatar
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    the first one is more angular, the second is more aestically appealing - as far as it goes lol

    That said - you'd need to see them both in place and workig to make a proper choice :-)
    Aesthetics also depend on surrounds and how well a thing fits them :-)

  8. #8
    I have an STL of the gear arm posted on the inverted delta thread (it's why I revived it). It uses the second type of chamfer as it does eat up less of the gear and I figured that was more important than the angular look I liked of the first one, especially since the gear ended up narrow than expected.

    I have since done a slight redesign of the gear arm to slim down some parts, add some mounting holes I'd forgotten and add some clearances for the things that go in those mounting holes I forgot. It looks a little sleeker now and will use a bit less material. In the end I'm hoping to design it with 'struts' built into the model so it can be printed with 0% infill and be strong enough.

    It came to mind that infill isn't really optimized as in denser in high stress areas, or orientated with how the loads will be. As such I'm trying to make it s the part can be printed hollow and the walls of all the struts provide all the strength necessary. Currently working on the shoulder, which turns out is a bit more complicated than I thought in terms of getting it printable without supports (mine differs from the original, notice how there is no place to mount the motor on the arm (that's not one of the things I forgot) ?).

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