Raptor Tension Bars too Thin

For discussion of hand designs.
CarlUVaBME
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Joined: Fri May 22, 2015 6:24 pm

Raptor Tension Bars too Thin

Postby CarlUVaBME » Fri May 22, 2015 7:07 pm

My name is Carl Lewenhaupt and I am a Biomedical Engineering Student at the University of Virginia, and I have printed and assembled 3 raptors in my time working with E-nable. After I get the hand printed (which always takes longer than expected due to makerbot woes) and assembled, I try it out just to give a small quality control and I end up breaking that little bar on the underside of the fingers where the white nylon strings tie off. It just appears to be too thin to bear any real weight and when I try to flex the hand shut to grab something, it snaps.

This is such a small design detail that I wouldn't normally go into it, but the raptor is really a wonderfully designed prosthetic in its ease of assembly, and it is a shame that it is so close to working so well.

If there is any way to make changes to that for the entire design, just by making it 3 or 4 times thicker, I think the raptor could come out on top again as the hand that best embodies E-nables goals of accessible, 3D printable, prosthetics for those in need.

Thanks,
Carl

GreggDennison
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Joined: Mon May 11, 2015 1:36 am
Location: Falmouth, KY
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Re: Raptor Tension Bars too Thin

Postby GreggDennison » Sat May 23, 2015 1:49 am

I have made 3 Raptor Reloadeds and have never had an issue with my 8 year old breaking those. And he's been wearing his latest for 2 weeks straight. What shell thickness and infill are you printing at?

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andreas
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Joined: Thu Feb 12, 2015 4:55 pm

Re: Raptor Tension Bars too Thin

Postby andreas » Sat May 23, 2015 6:15 am

Carl,

No detail is too small when it might be causing a failure! To clarify, have you been printing Raptor Original fingers or Raptor Reloaded fingers? The Raptor fingers had trouble with the tie-bars snapping off, so the Raptor Reloaded fingers were designed with a more robust tie bar and we haven't seen any cases of that snapping. The Raptor Reloaded fingers are compatible with the Raptor Original if those are indeed the fingers giving you trouble. Do you have any photos you could share?

Andreas

CarlUVaBME
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Joined: Fri May 22, 2015 6:24 pm

Re: Raptor Tension Bars too Thin

Postby CarlUVaBME » Mon Jun 01, 2015 3:37 pm

I have not tried to print the raptor reloaded fingers yet, just the raptor, but this is due to the fact that the raptor reloaded file only comes as the whole assembly. Do you have any advice for breaking it apart?

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andreas
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Joined: Thu Feb 12, 2015 4:55 pm

Re: Raptor Tension Bars too Thin

Postby andreas » Mon Jun 01, 2015 4:51 pm

The fingers are cross-compatible, so you can either download and print the STLs or if you would like CAD source files, they are also available on the Thingiverse, under the "native CAD source files" heading at the bottom of the information page: http://www.thingiverse.com/thing:596966

CarlUVaBME
Posts: 4
Joined: Fri May 22, 2015 6:24 pm

Re: Raptor Tension Bars too Thin

Postby CarlUVaBME » Mon Jun 01, 2015 6:47 pm

I didn't realize that link on e-nable's website went to the raptor hand stl and not the source files. Thank you! I was not paying thorough attention while I was looking.


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