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. 2018 Sep;232(9):962-971.
doi: 10.1177/0954411918794734. Epub 2018 Aug 16.

Ten guidelines for the design of non-assembly mechanisms: The case of 3D-printed prosthetic hands

Juan Sebastian Cuellar  1 , Gerwin Smit  1 , Amir A Zadpoor  1 , Paul Breedveld  1
Affiliations

Ten guidelines for the design of non-assembly mechanisms: The case of 3D-printed prosthetic hands

Juan Sebastian Cuellar et al. Proc Inst Mech Eng H. 2018 Sep.

Abstract

In developing countries, prosthetic workshops are limited, difficult to reach, or even non-existent. Especially, fabrication of active, multi-articulated, and personalized hand prosthetic devices is often seen as a time-consuming and demanding process. An active prosthetic hand made through the fused deposition modelling technology and fully assembled right after the end of the 3D printing process will increase accessibility of prosthetic devices by reducing or bypassing the current manufacturing and post-processing steps. In this study, an approach for producing active hand prosthesis that could be fabricated fully assembled by fused deposition modelling technology is developed. By presenting a successful case of non-assembly 3D printing, this article defines a list of design considerations that should be followed in order to achieve fully functional non-assembly devices. Ten design considerations for additive manufacturing of non-assembly mechanisms have been proposed and a design case has been successfully addressed resulting in a fully functional prosthetic hand. The hand prosthesis can be 3D printed with an inexpensive fused deposition modelling machine and is capable of performing different types of grasping. The activation force required to start a pinch grasp, the energy required for closing, and the overall mass are significantly lower than body-powered commercial prosthetic hands. The results suggest that this non-assembly design may be a good alternative for amputees in developing countries.

Keywords: Additive manufacturing; biomechanical testing/analysis; limb prosthetics; mechanical design; non-assembly design.

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Conflict of interest statement

Declaration of conflicting interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Figures

Figure 1.
Figure 1.
A schematic drawing of the design concept used for the hand prosthesis.
Figure 2.
Figure 2.
(Left) Isometric view of the whipple tree mechanism. All connections are designed to be 3D printed with large play. (Right) Frontal view of the whipple tree mechanism.
Figure 3.
Figure 3.
Force transmission system to the finger, (blue) semi-circle leaf spring connected from the base of the finger to the whipple tree mechanism, (yellow) the first level of the whipple tree mechanism and connecting links, (red) the second level of the whipple tree mechanism and main driving link. The Bowden cable is connected to the main driving link.
Figure 4.
Figure 4.
Non-assembly prosthesis prototype after support removal. Each number represents the corresponding design principle used to build the part.
Figure 5.
Figure 5.
Printing direction of the hand prosthesis.
Figure 6.
Figure 6.
Grasping patterns. Pinch grasping (top left and right), power grasping (middle left and right), spherical grasping (bottom left), and tripod grasping (bottom right).
Figure 7.
Figure 7.
The mechanical assessment of the prosthesis: (a) input force versus pinch force and (b) cable displacement versus the input force of a closing-opening cycle.
See this image and copyright information in PMC

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