Design for the additive manufacture of a control lever with multimaterial 3D printing

Abstract

In this master's project, the design for the additive manufacturing of a joystick has been created to later be able to materialize it through multi-material 3D printing so as to obtain a sustainable and simple model to print. The printing technique that has been used is called Fused Deposition Modelling (FDM). The model contains integrated sensors to allow linear and circular displacement. Two different materials have been combined, one conductive for the manufacture of the sensors and another structural for the manufacture of the rest of components. In the sensory part, resistive sensors have been designed to identify linear motion so that when the joystick is moved in one direction, the sensors perceive a traction or compression tension to give an electronic response. For circular motion, capacitive sensors have been designed so that one electrode is integrated into the lever and the other electrode into the joystick body. Theoretically, when a torque is applied to the lever, these electrodes form a capacitor that varies according the applied torque. In the initial phase of the project, bibliographical research has been carried out and the necessary printing parameters have been identified. After this, the design phase has been carried out, where different models have been created analysing all the components and their functionalities in order to obtain an effective and simple model. Some initial tests have been done with PLA to analyse the finish and quality before proceeding to the final printing. Three different geometry and component designs have been created. Design 3 has been the definitive one to be printed. The materials to be used for the printing were structural TPU and conductive TPU. Once printed, the sensory part has been configured. It has focused on circular motion using capacitive sensors since resistive sensors were developed in previous projects, so the linear motion was not included in the project scope. Four possible methods have been identified for measuring capacitance. Three methods based on the RC circuit and the last one based on the LC circuit. The first RC method identified distinct values but only in high value ranges. The second method using a 555 timer has failed due to unidentified internal electronic errors. However, the third RC method, which uses a 741 comparator, works correctly from 100 picofarads measures an above. The last method, based on LC circuit, has also been effective with similar range to the 741 method. It has been tried to test the joystick and no measurements could be detected. For this reason, it has returned to the design phase to rectify the last design and reduce the probability of failing in the measurement, although due to lack of time it was not possible to print the last design or analyse the results. Finally, the economic analysis and the environmental impact produced by the manufacture of the model have been carried out