METIS is a first light mid-infrared instrument for the new ESO/ELT telescope. It includes a cryostat with a mass of more than ten tons that must face the telescope optical beam placed 6 m above the telescope Nasmyth instrument mounting platform. To overcome this height and allow the overall alignment of the field and pupil of the entrance beam, a large size structure has been designed, analyzed and optimized and is now being manufactured. To minimize the overall mass, the beam attachments do not fit in a vertical/horizontal grid but are oblique in a 3D structure. In building this structure one needs to combine 3D CNC machined parts of reasonable dimensions with several welded structural tube structures. Due to the sizes involved, these subsystems must be manufactured accurately within an angle tolerance of 0.1 degrees, imposing challenges on the welding process. The overall approaches to the main problems, together with the structures needed for the assembly, integration and transport are discussed.
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