Method for preparing negative pressure film-covering frozen sand mold

A method for preparing a negative pressure film-covering frozen sand mold, comprising:

• step 1:
• numerically cutting a frozen sand blank mixed with water directly in a low-temperature machining environment through a numerical model-free freeze casting technology based on a cutting shaping principle to obtain upper and lower boxes of a sand mold, wherein in step 1, the frozen sand mold is provided with an air extraction hole, wherein the air extraction hole is directly drilled out on a side wall of the sand mold by numerically controlled machining;
• step 2:
• fixing the prepared frozen sand mold in an air extraction sand box that matches the sand mold in size, and brushing a surface of a mold cavity of the sand mold of the upper and lower boxes with a layer of thermal insulation coating;
• step 3:
• heating a thin film at 70° C. until softened to cover the surface of the mold cavity of the sand mold brushed with the thermal insulation coating;
• step 4:
• covering an outer surface of the sand mold with a back film to seal the sand box;
• and
• step 5:
• starting a vacuum pump to provide vacuum suction force, so that the thin film tightly adheres to the sand mold;
• covering the upper and lower boxes of the sand mold with a film under negative pressure, and then closing the upper and lower boxes to obtain an integral sand mold, wherein the thin film comprises polyester amine fibers, wherein a junction of a parting surface and the thin film is bound with an adhesive tape.