The purpose of this project is to reduce the cost and the weight of the Hosmer Prosthetic Model 5X Hook by 3D printing a redesigned version. It is important because the result of this study gives lower-middle income countries a more accessible and more affordable prosthetic. The Hosmer 5X Hook was scanned on a Solutionix C500 3D Scanner, surfaced on Geomagic Wrap and reversed engineered in Geomagic Design X. The Finite Element Analysis (FEA) was done on Solidworks. [Still need key results]
Introduction
The World Health Organization developed a set of criteria to ensure that biomedical devices, such as prosthetics, are applicable to lower-middle income countries. That criteria is ASSURED–Affordable, Sensitive, Specific, User-friendly, Rapid and robust, Equipment-free and Deliverable to end-users to ensure that biomedical devices are applicable to lower-middle income countries. Prosthetics for low-resource settings need to be simple, easy to manufacture, repair cheaply and provide amputees with increased function. Furthermore, they need to be equipment-free with no electronic components in order to decrease the complexity, fragility and cost. Electronics are not robust in varying weather. The Hosmer Prosthetic Model 5X Hook, depicted in Figure 1, accomplishes several aspects of the ASSURED criteria. The design is sensitive, specific and user-friendly, only needing a pulling force to activate its function. The prosthetic is also robust, utilizing only one pivot point with simplistic gripper designs. The Hosmer 5X Hook also does not require any electronics and is available to be purchased online, making it easily deliverable to most consumers. Nevertheless, the design can be improved by reducing the cost and the weight of the Hosmer 5X Hook. The hook is made of stainless steel and weighs 213 grams. It costs anywhere from $420 up to $585. While that may be affordable for some people, that price tag can be a stretch for lower-middle income countries. Decreasing the weight would make it more sensitive and user-friendly, being more comfortable to the user. Thus, the objective is to reduce the cost and weight of the Hosmer 5X Hook while maintaining the universal attachment to the wrist unit, the design efficiency and the gripping force.
Figure 1: Hosmer Prosthetic Model 5X Hook, Stainless Steel
The objective is accomplished by 3D printing a redesigned version of the prosthetic. 3D printing is a simple manufacturing method that improves on the affordability, rapidness and deliverability aspects of the ASSURED criteria. The cheaper material and process repeatability drives the cost down while the actual printing process is faster than manufacturing stainless steel. Prosthetists and patients can print out their own models at home or in the office, offering improved deliverability. The redesign is required to maintain the structural integrity of the prosthetic which altered due to the material change that decreases the weight. Accomplishing these objectives is important because it would drastically decrease the cost of the prosthetics, making it easily accessible to lower-middle income countries. It is expected that the 3D printing and truss system redesign will be able to fulfill the Hosmer 5X Hook’s functional capabilities in terms of loads and decrease the overall cost.
Theory
ABS material was used with the 3D printing because it is durable and can withstand varying temperatures and precipitation from the environment. Approximately 5 pounds of force is needed to hold a small object within the grasp of a Hosmer 5X Hook so the 3D printed prosthetic needs to be able to withstand that load and the physical wear and tear from daily activities. Finite Element Analysis (FEA) was performed on the 3D CAD models to test the deformation when 5 pounds of force is exerted on the inside of the hook. The results are used to see how we can minimize the maximum displacement, stress and strain. It is hypothesized that 3D printing will cost less than the original prosthetic and that the truss system redesign will be able to withstand 5 pounds of force. The redesign decisions are based on the deflection (1) and the second moment of area for torsion (2) formulas.
Procedure
Materials and procedures
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Results
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Discussion
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Data interpretation
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Conclusions
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References
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Appendices
Detailed sample calculations and data reduction
Original Data Sheet
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