[en] Coordinate measuring arms (CMA) are one of the most versatile metrological instruments on the market. Currently, they are mainly used in industrial manufacturing for quality control processes or reverse engineering. Their utility, combined with high-performance in terms of measurement precision and repeatability, makes their price unaffordable for the average consumer. Having this in mind, this project is based on the need to measure relative positions (distances and coordinates) between points on medium-sized parts, such as a motorcycle chassis. Through the PREDICA industrial project management methodology, this document shows the design and manufacturing process of a three-dimensional coordinate measuring instrument (articulated arm type) to obtain a functional prototype. The precision to be achieved must be equal to or less than one-tenth of a millimetre (±0.1 mm). The project will start with Strategic Engineering, conducting market studies and material research. Possible manufacturing processes and associated technologies will also be introduced on it. Subsequently, Concept Engineering will move to the analytical and creative planning phase, generating different design proposals for the measuring arm in the form of sketches. In the detailed engineering phase, the chosen arm alternative will be developed, creating a three-dimensional model using a CAD software (SolidWorks); this is the formal prototyping stage where the modular design is created, piece by piece. Commercial and standardized components will also be incorporated. The electronic circuit on which the arm's operation is based on will also be designed. This includes several elements, with optical encoders and a microcontroller being the most prominent ones. The encoders measure angular displacements at the arm's joints, while the microcontroller runs the measurement software and coordinates the action of peripherals to deduce the position of the probe at the end of the arm. To increase the measurement precision of the encoders has been planned the implementation of a resolution enhancement mechanism through a cycloidal multiplier. In the subsequent Execution Engineering stage, production becomes possible through calculation and simulation. This allows for the proper sizing of mechanical components. The necessary technical documentation for manufacturing will also be generated. Another goal is the full support and validation of the decisions made with sufficient information and documentation. The primary manufacturing technologies are fused deposition modelling (FDM), particularly, and machining. In line with these and the analysed design requirements, the predominant material will be PLA (3D printing filament). PVC and aluminium, both in tubular commercial form, will also be used. In the final Manufacturing Engineering stage, the construction of the necessary components for the prototype's operation will take place. In parallel, a series of experimental processes (tests) will be carried out to verify the sizing and properties of materials and modular design units. In conclusion, this project has become a direct and tangible application of the technical knowledge acquired by the student during their university learning. At the same time, it represents an immense self-learning process. It has allowed the understanding of the complexity behind the design and realization of a product. However, despite obtaining a functional arm prototype, the measurement accuracies achieved are far from the target. One of the main reasons is the challenging-to-measure and control manufacturing tolerances resulting from FDM printing. The desire for maximum cost optimization, reflected in low-performance electronic components, has also influenced this. Likewise, the measurement software itself, developed from scratch and based on limited knowledge, presents inefficiencies.

[es] Los brazos articulados de medición por coordenadas (BAMC) son uno de los instrumentos metrológicos más versátiles del mercado. Actualmente, se implementan principalmente en centros de fabricación industrial para procesos de control de calidad o ingeniería inversa. Su utilidad, junto con un alto rendimiento en términos de precisión y repetibilidad de la medición, provoca que su precio en el mercado sea inasequible para el consumidor común. Con esto en mente, este proyecto se basa en la necesidad de medir posiciones relativas (distancias y coordenadas) entre puntos en piezas de dimensiones medianas, como el chasis de una motocicleta. A través de la metodología de gestión de proyectos industriales PREDICA, este Trabajo de Fin de Grado documenta completamente el proceso de diseño y fabricación de un instrumento de medición tridimensional por coordenadas, de tipo de brazo articulado, para obtener un prototipo funcional. La precisión de la medición a lograr debe ser igual o menor a una décima de milímetro (±0,1 mm). Se partirá de la Ingeniería de Estrategia realizando estudios de mercado, de materiales y del estado del arte. También se introducirán posibles procesos de fabricación y tecnologías implicadas. A continuación, se procederá a través de la Ingeniería de Concepto a la planificación analítica y creativa; se elaborarán una serie de propuestas de diseño de brazo de medición en forma de bocetos. En la Ingeniería de Detalle siguiente, se desarrollará la alternativa de brazo elegida, elaborando un modelo tridimensional con software CAD (SolidWorks); es la etapa del prototipado formal, en la que se genera el diseño modular, pieza por pieza. Se tendrá en cuenta la participación de elementos comerciales y normalizados. También se proyecta el circuito electrónico en el que se basa el funcionamiento del brazo.