The ARM (Auckland Version) #5
It's here The Wrist. Took a bunch of time. 1 day to be exact. Yes Sir/Belle demoiselle the god (with a non capitalized 'g') needs his judgement for his sins and I shall deliver it to that dammned soul.
The wrist was made in one evening, it was made in complete <panik> because I accidently FORGOT about making the wrist ahahahahahhahah.
l'enfer c'est les autres
The Wrist is very simple, doesn't need much fancy work of explanation.
Essentially it's just two servos hooked together which rotate a lever at one point of rotation in 2 DOF. One of the servos uses a belt to rotate the one which is directly connected to the lever (palm).
Nothing much else, things are connected by bolts ofcourse, very nice bolts.
Below the complete 3D assembly (Interactive) is provided for developing understanding.
१| Belt Tension Design
Starting off with the model of the design, its quite straightforward, a belt, a few bearings and two rods with flat screws.
The magic was the two rods pretensioning and tensioning the belt according adjusted according to the length used. The design ended up pretty good for a first try, if I made a version 2 of it, I would make the adjustable rod length much wider and the pre tension distance much further.
I used two bearings on one rod because the belt's width was exactly two MR84 bearings wide. Only had MR84 bearings that evening. With the deadline for demo being the next day, couldn't get any other bearing.
२| The Manufacturing Methods
The entire thing was primarily manufactured from SLS printed Nylon. It was first made in the labs of AUT and then sent to JLCPCB. The sandblasting availability in JLCPCB made it have a very good texture.
SLS was chosen due to the very 3D ish nature of the whole thing. There was no one flat surface where the part could be referenced to the plate on FDM and SLA to. Hence printing in powder as the first choice.
Nylon being a very resilient material proved to be the best contender for the high tension mechanism of the wrist.
३| I Actually Dont Know...
The hand was a great project. I loved making it. This subassembly - The wrist as the last part of the hand to be finalized. It took two tries to make it more resilient but it worked somehow.
The tensioning mechanism was one of the things I came up on spot and I am proud of it. The dual point tensioning system with one being fixed and one being variable worked so nicely and retained the 8 bit percision was mindblowing to look at in reality.
Anyways, what's good will always be good and I don't know why it will be good.
- Made in A.U.T. Room 1552, New Zealand by RolandThsive
Have a nice day,
- Rohit
YOU CANNOT MAKE THIS IN ONE EVENING
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