Investigation of Discharge Characteristics of Hinges Produced with 3D Printing for Prosthetic Fingers

Flexible hinges are joint mechanisms made of soft or flexible materials. The aim of this study is to determine the discharge characteristics of the flexible hinges used in prosthetic hands and fingers according to the production techniques and to determine the most appropriate hinge production parameters. The speed of the opening process and the energy consumption during the closing process directly depend on the structure of the flexible hinge. For this reason, it is important to examine the relationship between the change of the flexible hinge structure and its discharge in terms of oscillation and energy requirement. In the method of the study, primarily flexible hinge samples are produced using different printing parameters. In the next step, a finger-like test system is designed that uses accelerometers to measure discharge oscillations on the fingers. The test mechanism has a body and a free accelerometer. The body sensor is used to distinguish body vibrations transmitted to the free accelerometer. As a result of the measurements made with the test system, it is observed that the honeycomb shape produced higher frequency vibrations than the linear shape in terms of filling the shape. This indicates that the honeycomb filler can store a higher amount of energy as a result of stretching. As the percentage of inner fill or the number of outer shells increased, the frequency of vibration of the flexible hinge when released is found to be higher. It has been concluded that the hinge, which has the highest energy storage capacity at the lowest cost, will have a honeycomb filling shape, 30% filler, and four shells. Finally, a system that measures the power consumed for finger closing operations is presented. As a result of energy consumption levels with hinges, it has been observed that energy consumption increases as infill density and number of shell values increase. It is seen that these values are compatible with oscillation values. With this system, it is aimed to be used for parameter selection in robotic prosthetic finger application which is planned to be produced by 3D printing in the future.