Application of Contour Fitting Method in CFETR VV Assembly

China Fusion Engineering Test Reactor (CFETR) vacuum vessel (VV), which is welded from forming shells and ribs, is a toroidal double shell structure device. However, there are manufacturing errors in the forming and welding processes that will lead to accumulative deviation of the VV dimensions and affect the VV contour. In order to reduce and decentralize errors, the surfaces of welded parts are measured and then fit with least-squares method. According to the fitting result, new benchmarks are reset in the form of controlling points for the next assembly. This paper is about the application of contour fitting method in manufacturing of the first 1/32 VV sector of the CFETR 1/8 VV mock-up.