Cosmetic Terminal Devices

For discussion of arm designs.
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Skip Meetze
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Cosmetic Terminal Devices

Postby Skip Meetze » Mon Feb 01, 2016 9:59 pm

Cosmetic Terminal Device Notes
Updated: 7 February 2016 Sunday


At the Autodesk Summit in January, the Bay Area e-NABLE designers recognized that
  • The appearance requirements for hands and arms will vary from region to region around the world.
  • The psycho-social function of an assistive device is always important but sometimes it is the most important function determining the design requirements.
  • The robot and super-hero appearance of our most popular wrist-powered hands is not appropriate for some people that we would like to serve.
  • For our Haiti project, hands and arms must look real (and thus will not draw unwanted attention) or they will not be used.
Therefore, it will be useful to develop realistic-looking hands for use as Terminal Devices (TDs) on our modular Training Arm system. With the standard 1/2 inch (or M12) fine thread screw connection, the realistic-looking TDs can also be used on conventional prosthetic devices.

Cosmetic Terminal Devices for the Modular Training Arm

Cosmetic Hand .6 assembly.png
Cosmetic Hand .6 assembly.png (99.6 KiB) Viewed 1992 times


This variation of the Gripper Thumb Hand has advantages of
  • realistic appearance,
  • working with the Training Arm or conventional prosthesis,
  • reasonable durability,
  • ease of fabrication,
  • ease of use, multi-task utility, etc.
  • and by virtue of being printed flat (strong and no support needed),
  • and having only one moving part.

GT hand 1.6 assembly.png
GT hand 1.6 assembly.png (187.33 KiB) Viewed 1992 times


The Cosmetic Hand https://tinkercad.com/things/4kRNNkahyO0
and the 2-Part Gripper Thumb Hand https://tinkercad.com/things/kdrKncmw3YR
will work with the Modular Training Arm System and will allow an additional range of terminal devices in the e-NABLE tool box to meet specific appearance requirements.

As my OT friend David Dietz once pointed out, such a cosmetic hand can also be functional for a transradial amputee in tasks like carrying a shopping bag with the elbow flexed and grasping the bag’s handle in the cruck of the thumb. This carrying position can help prevent the prosthesis from slipping off the residual arm while carrying.

The devices were remixed using Tinkercad from the “heart hand love hand” by taherizad stl files, published on Thingiverse in Apr 25, 2015 http://www.thingiverse.com/thing:792576

heart hand love hand.jpg
heart hand love hand.jpg (74.03 KiB) Viewed 2024 times


These devices have the fabrication advantages of the other printed-flat devices, but the distal ends of the fingers will have a cross-grain and they may not be as resistant to breaking as the fingers of the thermoformed Terminal Devices.

STL files were updated 7 February 2016
and they can be found here
https://drive.google.com/folderview?id=0B3VhDqFhSJU9OFF6REVKWnFQM2s&usp=drive_web
and they will be updated frequently as the designs evolve in the next few weeks.
Last edited by Skip Meetze on Mon Feb 08, 2016 1:17 am, edited 9 times in total.

john.diamond
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Re: Cosmetic Terminal Devices

Postby john.diamond » Wed Feb 03, 2016 9:21 pm

I've printed the cosmetic gripper hand and it took 14:41 on my RepRap. I'm not sure the thumb hinging is correct as it only closes as far as shown in the photos. The thumb has very little range of movement and can't touch the fingers. The hand looks very lifelike and I'm sure can be adjusted to work as intended. Note that the wrist bolt hasn't been attached using filament yet.
Cosmetic Gripper 1.jpg
Cosmetic Gripper 1.jpg (364.84 KiB) Viewed 2039 times
Cosmetic Gripper 3.jpg
Cosmetic Gripper 3.jpg (358.72 KiB) Viewed 2039 times
Cosmetic Gripper 2.jpg
Cosmetic Gripper 2.jpg (347.12 KiB) Viewed 2039 times

john.diamond
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Re: Cosmetic Terminal Devices

Postby john.diamond » Fri Feb 05, 2016 1:49 am

I've identified why the thumb won't close and it's not the pivot hole position as that's OK. There's a small protrusion from the side of the slot into which the thumb is placed and I've ringed it in red in the first photo. The other photos show the fully assembled hand with the castrating band and rivets added.
Gripper Hand Problem.jpg
Gripper Hand Problem.jpg (130.68 KiB) Viewed 2030 times
Gripper Hand 2.jpg
Gripper Hand 2.jpg (110.05 KiB) Viewed 2030 times
Gripper Hand 1.jpg
Gripper Hand 1.jpg (144.52 KiB) Viewed 2030 times
Gripper Hand 3.jpg
Gripper Hand 3.jpg (98.25 KiB) Viewed 2030 times
Gripper Hand 4.jpg
Gripper Hand 4.jpg (106.6 KiB) Viewed 2030 times

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Skip Meetze
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Re: Cosmetic Terminal Devices

Postby Skip Meetze » Fri Feb 05, 2016 1:03 pm

Thanks John! Looks like a successful proof-of-concept to me! Congratulations!!!!

Let me point out that this was the 2-Part Gripper Thumb 1.3 set. I am updating the sticky posting at the top of this forum with v 1.5.

My friend Dower Chin and his son Isaac have successfully printed the 2-Part Cosmetic Hand on 4 January 2014 in ABS on his Lulzbot Mini. Congratulations Dower!. Another proof-of-concept!
Attachments
Dower's print of Cosmetic Hand 1.3.jpg
Dower's print of Cosmetic Hand 1.3.jpg (109.78 KiB) Viewed 2025 times

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Skip Meetze
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Cosmetic Terminal Devices also work for Transhumeral arm systems

Postby Skip Meetze » Fri Feb 05, 2016 7:09 pm

In addition to the Modular Training Arm http://forums.e-nable.me/viewtopic.php?f=8&t=232 (a transradial elbow-powered arm), another application of Cosmetic Terminal Devices is for Transhumeral Modular Arm systems and the two systems can share much of the same technology. The Haiti Team is actively seeking this type of device.

Transhumeral assembly 1.0.png
Transhumeral assembly 1.0.png (156.39 KiB) Viewed 2015 times


The parts can all be printed or some can be printed flat and thermoformed (or thermoformed from flat sheets printed with a flatbed inkjet printer).

The socket will be fabricated by a prosthetist and attached to the Above Elbow Plug or the Upper Arm Cuff.

The wrist can pronate and supinate as the recipient twists it with the other hand. The wrist and forearm may benefit from adding a flexible cosmetic fairing that gracefully makes the transition from the oval/rectangular form of the wrist to the more circular cross-section of the forearm

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Skip Meetze
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Assembly experiments with the cosmetic hands:

Postby Skip Meetze » Mon Feb 08, 2016 9:12 pm

  • Thermoforming one part of the cosmetic hand to get it to fit precisely with the other is a bad idea! The part shrinks in an uncontrolled way and the fit is likely to get worse rather than better.
  • Solvent bonding the 2 flats together (with pegs and the screw for alignment) is good when you are ready to make it one solid piece.
  • Use wooden pegs (such as 1/8 inch bamboo skewers from the grocery store) so the alignment pegs will not be welded permanently.
  • The bonding acetone is also good for layer adhesion and for strength in the fingers too.
  • However: We need a way to get back the matt finish after the acetone bath for realistic hands and arms. Gloss finish is nice for robot hands and super hero hands but does not look like skin.

Bad idea.jpg
Bad idea.jpg (147.88 KiB) Viewed 1984 times

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Skip Meetze
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Re: Cosmetic Terminal Devices

Postby Skip Meetze » Thu Feb 11, 2016 6:37 pm

Problem:
The 2-Parts of the cosmetic hand designs are coming off of the printer with a bow in the middle due to normal stresses of parts of varying thickness during cooling. Attempts at softening the parts to thermoform them flat resulted in uncontrolled shrinkage so the parts no longer matched.

Potential solution:
Note: v 1.7 and v 1.8 were discarded in a revision posted on 16 February 2016 because of errors.
  • Hollow out the back side of the hand so that the walls are a more nearly uniform thickness.
  • Hopefully the design can be printed without support (due to the sloping archway shape and the screw posts in the middle).
  • The thin walled parts should be resilient enough to be flattened to the mating surface with screws.


v1.9 underside.png
v1.9 underside.png (946.98 KiB) Viewed 1933 times


We are still working with the child size (small) hand because it is faster to print than the adult female (medium) size

We need alpha testers to try printing and assembling the parts. The assembly is similar to the Gripper Thumb. Please report your findings on this thread.

2-Part Gripper Thumb hand LS set (left, small)
STL files https://drive.google.com/open?id=0B3VhDqFhSJU9UENrdjJOYWlLbm8 and
Tinkercad Files https://tinkercad.com/things/jm67urQnRiv

2-Part Gripper Thumb hand RS set (right, small)
STL files https://drive.google.com/open?id=0B3VhDqFhSJU9RVU1ZWl5QWNYeG8 and
Tinkercad Files https://tinkercad.com/things/aGP6dXPfeNv

2-Part GT hand 1.9 LS set.png
2-Part GT hand 1.9 LS set.png (251.68 KiB) Viewed 1933 times

2-Part GT hand 1.9 RS set.png
2-Part GT hand 1.9 RS set.png (155.84 KiB) Viewed 1933 times
Last edited by Skip Meetze on Tue Feb 16, 2016 9:34 pm, edited 3 times in total.

PeterBinkley
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Joined: Fri Feb 13, 2015 5:49 pm

Re: Cosmetic Terminal Devices

Postby PeterBinkley » Thu Feb 11, 2016 9:59 pm

Skip,

Sorry about the color. I don't have any skin-tone ABS, so I used this neon yellow.

I printed with a large brim, which helped control warping, but didn't eliminate it.

I used ABS cement (abs+acetone) to glue the sides together. I should have worn gloves. I used a #6 sheet metal screw to squeeze the halves together. When the glue dries, we will see if it helps shrink the halves together. I'll definitely need to fill some holes when this cement dries.

ABS and nylon both shrink as they cool, so I think for this design, it will make sense to print the whole thing at once, and to include support in the model. Or we could suggest printing with support turned on. Gluing two halves together is a challenge, and I think it will negatively impact the quality of the product and/or ease of assembly.
Attachments
2-parthand01.jpg
2-parthand01.jpg (120.73 KiB) Viewed 1960 times
2-parthand02.jpg
2-parthand02.jpg (192.38 KiB) Viewed 1960 times
2-parthand03.jpg
2-parthand03.jpg (179.39 KiB) Viewed 1960 times

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Skip Meetze
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Re: Cosmetic Terminal Devices

Postby Skip Meetze » Tue Feb 16, 2016 10:46 pm

TD demo video.png
TD demo video.png (1.43 MiB) Viewed 1931 times


Take a look at the video of the Terminal Device in action.
https://drive.google.com/open?id=0B3VhDqFhSJU9b2ZvOTcwNGVrZ2dvSVQ1NXJYMFRDdGZSMENr

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Skip Meetze
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Re: Cosmetic Terminal Devices

Postby Skip Meetze » Sun Feb 21, 2016 11:47 pm

Uploaded new design for TD:
My thanks to Peter Binkley for the idea to print (using support) with the edge of the palm against the bed of the printer for controlling the grain in the fingers.
  • Not yet printed, but wanted to share for others to test.
  • Wrist pivots to flex and extend. This allows grasping without awkward body positioning.
  • Printing with palm resting on its side (edge against the bed) allows grain to be parallel to fingers so that they will be stronger.
  • Requires support to print.
  • Cosmetic design has a somewhat compromised thumb appearance.
  • Griping range from soda can to small object.
  • 3/8 inch bolt holds wrist pivot. Lock nut adjusts friction against o-ring to control ease of changing (wrist flex-extend) position.

Side Print Wrist Assembly.png
Side Print Wrist Assembly.png (239.13 KiB) Viewed 1915 times

Made a video of rotating Tinkercad model.

model movie https://drive.google.com/file/d/0B3VhDqFhSJU9QmMtUE5SamFkZm8/view
STL files https://drive.google.com/folderview?id=0B3VhDqFhSJU9Y29BTlFVbm5URU0&usp=drive_web
pictures https://drive.google.com/folderview?id=0B3VhDqFhSJU9bFJKdHlfcTR6WEE&usp=drive_web
UM2 Gcodes https://drive.google.com/folderview?id=0B3VhDqFhSJU9WXY5SS0xZ3dFQ3M&usp=drive_web


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