The invention discloses a manufacturing method for a large thin-walled
impeller. An upper mold body of a mold is internally provided with annular grooves and exhaust plugs so that exhausting can be improved, a cooling cone is arranged on the upper mold body and cooling rings are arranged on the upper surface of the upper mold body so that the
cooling speed of castings can be increased, and meanwhile a sand mold is used at the bottom of a
gypsum core so that heat preservation of molten aluminum at the bottom and feeding of the castings can be facilitated. The program allowing integral
casting of the thin-walled and large-size
impeller to be achieved by improving exhausting and cooling is adopted for the mold, the forming quality is good, and precision is high; a first concave part is arranged to position the first
circular face of the end portion of the
impeller, the impeller is locked to a bottom plate through first pressing pieces,
welding is not needed, and fixation is convenient and rapid; and after the first round of
machining is conducted on the impeller, a second concave part is arranged to position the second
circular face of the impeller, fastening is conducted through second pressing pieces,
machining is conducted on the impeller in order, the situation that some faces are not machined due to clamps or other reasons is avoided, and the surface precision of the impeller is improved.