Low Profile Gripper Box

For discussion of hand designs.
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Jacquin Buchanan
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Joined: Thu Aug 18, 2016 3:10 pm
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Low Profile Gripper Box

Postby Jacquin Buchanan » Wed Aug 31, 2016 2:41 am

Here is my latest version of a low profile gripper box.

Low Profile Gauntlet with tensioner screws.png
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This design thermoforms very well. There are virtually zero flat spots.
IMG_1359.jpg
IMG_1359.jpg (594.76 KiB) Viewed 2375 times


This adds the bolts for tension adjustment. I designed the bolts around M2, M3 and M4 bolts. These are pretty readily available with various head types and lengths. The fabrication guide would have to include a table of the scale of prints and the required size bolts. The bolts are meant to spin freely in the plastic. So those holes will have to be drilled out after printing for many sizes. The end nut should be a locknut. It is the captured nut in the whippletree that moves.

The cover seen in the photos is printed separately and thermoformed, then will slide in the slots.

IMG_1363.jpg
IMG_1363.jpg (703.25 KiB) Viewed 2375 times

IMG_1362.jpg
IMG_1362.jpg (835.47 KiB) Viewed 2375 times


I wrestled with this design for a while, because I thought it was too exposed, until I added the cover. I like the cover because it makes the design more ascetically pleasing while protecting the small parts. It also allows adding theme elements to the cover itself.

The cover holds on pretty well, but would be the first thing to break off after heavy use. My guess is this is ok.

The sliding parts are very small. They could be difficult to print at sizes smaller than 130% for some printers.

The bolt attachments are small. I want to test how much force it takes to pull these bolts off. I don’t think it is possible to pull them off by over forcing the actuation of the hand. But I plane to test to its limit and see. Breaking these parts off by whacking the back of the wrist against a hard surface is most likely, hence my adding the cover.

I could add more plastic around the bolt attachments without affecting thermoform-ability. This might negate the need for a cover. But, I like hiding the bolts anyway.

I am willing to post this to thingiverse if anyone else would like to test it with me.

Krzys59
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Re: Low Profile Gripper Box

Postby Krzys59 » Wed Aug 31, 2016 9:16 pm

Interesting idea, could you publish source?

RichWP
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Re: Low Profile Gripper Box

Postby RichWP » Wed Aug 31, 2016 11:11 pm

I'd be happy to help with testing... Note that I've only just passed QA on my test hand - so I don't have a ton of experience with the different designs - but I do have a couple of years in both 3D printing and CAD.

Jacquin Buchanan
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Re: Low Profile Gripper Box

Postby Jacquin Buchanan » Thu Sep 01, 2016 3:09 pm

Krzys59, Yes, I will definitely publish STL files and Fusion 360 files on thingiverse. I have a day or two more of tweaking then I'll put it up there and post the link here. Look for it this weekend.

I am pulling the one in this photo apart with a force meter. I am finding a few spots I want to thicken up before posting.

RichWP, I'd love anyone to build it. One concern I have is that the moving parts are too small for some printers.

Jacquin Buchanan
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Joined: Thu Aug 18, 2016 3:10 pm
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Re: Low Profile Gripper Box

Postby Jacquin Buchanan » Fri Sep 02, 2016 4:43 am

OK The source files are now available on Thingiverse

http://www.thingiverse.com/thing:1749293

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Skip Meetze
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Location: Webster, NY
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Re: Low Profile Gripper Box

Postby Skip Meetze » Sat Sep 17, 2016 5:50 pm

Well done Jacquin! This is an interesting alternative to the whippletree for adaptive gripping and I like it! I look forward to hearing from your beta testers.

Jacquin Buchanan
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Re: Low Profile Gripper Box

Postby Jacquin Buchanan » Sun Sep 18, 2016 8:16 pm

Thanks Skip. I call this a soft whippletree. It still has the same adaptive behavior as the hard whippletree. I have been busy on other projects so haven't had time to promote testing. I need to get out an encourage more people to try it.

I am going to make a three pin version too. This whippletree version is a bit hard to assemble. The three pin version should be easier to print and assemble and have almost as mush adaptive grip as the whippletree.


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