The Recreation and Evaluation of a Human Hand Using Low-Cost Reverse Engineering and 3D Printing Systems

Abstract

The primary goal of this research was to evaluate the effectiveness of a low-cost reverse engineering system to recreate a physical, three-dimensional model of a human hand. In order to achieve the goal of this research, three key objectives were fulfilled: (1) the first objective was to recreate the physical model of the human hand using a low-cost experimental setup (<$5000), (2) the second objective was to assess the ability of the reverse engineered hand to perform common tasks of everyday life, and (3) the third objective was to investigate the potential biomedical applications of the reverse engineered human hand. A chosen test subject had his or her hand molded and cast into a plaster three-dimensional model that could be held steady and scanned very precisely by a NextEngine Desktop 3D Scanner. Other methods could have been employed to achieve the scanned model, but given the experimental setup and timeline a casted model was assumed to be the most appropriate method to achieve the best results. The plaster casting of the subject’s hand was scanned several times using different orientations of the model relative to the stationary 3D scanner. From these scans, a computer CAD model of the human hand was generated, modified, and 3D printed using a Makerbot Replicator 2. The printed model was evaluated by its ability to perform common every-day tasks such as picking up a cup/bottle, holding a pen/pencil, or opening/closing around an object. Several iterations of the printed human hand were evaluated in order to determine the best design for the fingers’ joints and cable-driven motion system. The first iteration of the printed hand featured a snap-in joint system. This joint design suffered from requiring a large number of individual pieces and poor tolerances of the Makerbot printer. The second iteration featured a press fit style joint system. This system was hindered by tolerances similar to the first iteration as well as plastic deformation of the printed material due to inadequate elasticity. The third and final iteration of the joint system featured a single printed assembly for which the entire prosthetic could be printed at one time. It was expected that the hand would be able to translate the rotational movement of an individual’s wrist to tension the cables of the motion system thereby closing the fingers into a first. This movement will allow the user to close the prosthetic hand around everyday objects and pick them up with relative ease. Although the possibilities of reverse engineering and 3D printing systems have greatly expanded as a result of greater affordability and increased accuracy, their applications in the biomedical field have yet to be fully explored.