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The DDRAGO instrument for COLIBRI 1.3 meter telescope of the Observatorio Astronómico Nacional in San Pedro Mártir, Baja California, México, will be installed in mid-2024. The structural design of DDRAGO was carried out by applying specific techniques for the development of astronomical instruments. At this work is decribed the mass budget, errors, and mechanical tolerances developed to fulfill the scientific objectives of DDRAGO, as well as the manufacturing methods carried out to satisfy the required geometrical specifications. Also, manufacturing processes such as grinding of reference surfaces of the structural plates, CNC manufacturing, precision drilling and tapping, and anodizing are described. The mechanical assembly of the mechanical support structure was performed in two stages. The first one, for verifying the correct integration of all the structural plates with each other and with the rest of the mechanical components that are supported by it. Then, to ensure compliance with the dimensions and geometric tolerances of the assembled structure before anodizing, the general dimensional metrology was performed with the use of a coordinate machine.
Once the structure was verified and accepted, anodizing was performed. An interesting aspect of this process is that we were able to measure the dimensional difference, as well as the repeatability of the assembly process, before and after anodizing. Finally, the dimensional acceptance reports of the DDRAGO instrument structure are shown and a series of guidelines for the manufacture, assembly, integration, and validation for mechanical structures in astronomical instrumentation are proposed.
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