Active Ball Joint Mechanism with Three-DoF Based on Spherical Gear Meshings (2021) | Hacker News Reader

Active Ball Joint Mechanism with Three-DoF Based on Spherical Gear Meshings (2021)

ieeexplore.ieee.org

51 pointsgnabgib18 comments

Was wondering if it's ABENICS (2021), and it is.

Video: https://youtube.com/watch?v=hhDdfiRCQS4

Holy cow... Hobbing gears like these looks like a nightmare. There's going to have to be some backlash, or some precision grinding.

Agreed. This design is going to be very very hard to machine precisely and very expensive to prototype

They don't even say exactly what they did or how long it took or how well the tolerances turned out. They only give the classic understated view:

"Many parts of the prototype were built from high-performance plastics with high machinability and stable properties because the components of ABENICS have complex shapes, which makes estimating problems during prototyping difficult. Construction from strong materials such as metals will also improve the capability of the device."

If they could make this work in plastic, it will be even easier to get the tolerances with metal. You can also mold the parts.

Casting and metal printing are the only options. And casting of gears is not a solution unless you're using exotic metals.

Can it even be cast? It looks like this would be really difficult to get to come out of the mold. Unless you go investment casting over die casting.

Anything can be cast if your budget allows for it. Ferrari engines are a good example.

It should be possible to make it by milling, even if that would waste a lot of material.

For casting, the initial mold must be made by milling anyway (or 3D printing), even if some intermediate molds could be made by casting themselves.

Eh, they make precision stuff like this all the time. If they wanted to make a bunch they would first standardize the sizing then create production tooling for the grinding setups. Those gears would come out basically perfect every time.

The bigger problem is the output link is supported by the gear meshes. This means whatever load you put on it is directly supported by the small mesh contact patches. A more traditional system can have roller or ball bearing or bushing support.

Exactly my thought. They're hand waving all complex manufacturing to 3D printers. This will be a hard plastic gear for the foreseeable future.

Previous HN discussion: https://news.ycombinator.com/item?id=34160356

Even more previous: https://news.ycombinator.com/item?id=28556208

What I find truly amazing here: an IEEE article where you can just click on the PDF button and actually read the article without hitting you head into a paywall.

Thankfully the open access model is becoming more popular, though I still find it insane that a lot of publishers demand a huge fee to publish articles as OA. I know they have to pay the bills and I guess it's better than ads, but they hardly even do anything anymore with online publishing and volunteer editors/reviewers.

It's 3 years later. Are these in use anywhere commercially?

When can I get my hip and shoulder replacements?

Won't this have lots of wear and tear?

(2021)

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