A void former is arranged in a mold (30). The void former includes an insert (1) made of flexible material that forms a loop around a core region (15) within the mold. Casting material is added in a fluid state into the mold so as to fill a predefined volume for the facing element, including the core region. After hardening of the casting material, the facing element (10) is removed from the mold, and the void former is removed from the facing element. The facing element comprises an anchoring core formed by the hardened casting material in the core region (15). Removing the void former comprises pulling the insert (1) away from a rear surface of the facing element (10). The flexible material of the at least one insert is deformed around the anchoring core (15) while it is pulled.

A void former is arranged in a mold (30). The void former includes an insert (1) made of flexible material that forms a loop around a core region (15) within the mold. Casting material is added in a fluid state into the mold so as to fill a predefined volume for the facing element, including the core region. After hardening of the casting material, the facing element (10) is removed from the mold, and the void former is removed from the facing element. The facing element comprises an anchoring core formed by the hardened casting material in the core region (15). Removing the void former comprises pulling the insert (1) away from a rear surface of the facing element (10). The flexible material of the at least one insert is deformed around the anchoring core (15) while it is pulled.

A method for preparing a negative pressure film-covering frozen sand mold includes: directly obtaining a mold cavity of a sand mold through numerically controlled machining of a frozen sand blank; covering a surface, brushed with a thermal insulation coating, of the mold cavity of the sand mold with a softened thin film, and covering an outer surface of the sand mold with a back film to seal a sand box; fixing the frozen sand mold in an air extraction sand box with a vacuum chamber, and extracting air through a vacuum pump, so that the thin film tightly adheres to the sand mold through vacuum suction force; and closing the box to obtain an integral sand mold, and pouring a casting at room temperature or low temperature under negative pressure. The method is environment-friendly, and the prepared frozen sand mold has high strength and is convenient for sand cleaning.

A method for preparing a negative pressure film-covering frozen sand mold includes: directly obtaining a mold cavity of a sand mold through numerically controlled machining of a frozen sand blank; covering a surface, brushed with a thermal insulation coating, of the mold cavity of the sand mold with a softened thin film, and covering an outer surface of the sand mold with a back film to seal a sand box; fixing the frozen sand mold in an air extraction sand box with a vacuum chamber, and extracting air through a vacuum pump, so that the thin film tightly adheres to the sand mold through vacuum suction force; and closing the box to obtain an integral sand mold, and pouring a casting at room temperature or low temperature under negative pressure. The method is environment-friendly, and the prepared frozen sand mold has high strength and is convenient for sand cleaning.

A void former is arranged in a mold (30). The void former includes an insert (1) made of flexible material that forms a loop around a core region (15) within the mold. Casting material is added in a fluid state into the mold so as to fill a predefined volume for the facing element, including the core region. After hardening of the casting material, the facing element (10) is removed from the mold, and the void former is removed from the facing element. The facing element comprises an anchoring core formed by the hardened casting material in the core region (15). Removing the void former comprises pulling the insert (1) away from a rear surface of the facing element (10). The flexible material of the at least one insert is deformed around the anchoring core (15) while it is pulled.

A void former is arranged in a mold (30). The void former includes an insert (1) made of flexible material that forms a loop around a core region (15) within the mold. Casting material is added in a fluid state into the mold so as to fill a predefined volume for the facing element, including the core region. After hardening of the casting material, the facing element (10) is removed from the mold, and the void former is removed from the facing element. The facing element comprises an anchoring core formed by the hardened casting material in the core region (15). Removing the void former comprises pulling the insert (1) away from a rear surface of the facing element (10). The flexible material of the at least one insert is deformed around the anchoring core (15) while it is pulled.

A casting method includes preparing a thin shell mold which is sintered and placed in a box. Sands are buried in the box to encompass the thin shell mold. The pressure chamber is depressurized. The casting material is filled into the thin shell mold, such that the thin shell mold is disposed at a vacuum state. Then, the negative pressure of the pressure chamber is released. Then, the pressure chamber is pressurized, to form a pressure difference which presses the casting material to flow into the thin shell mold, thereby finishing the casting work. The temperature of the casting material is reduced, and the pressure in the pressure chamber is increased. Then, the casting material is cooled to form a casting product. Then, the thin shell mold is broken, and the casting product is removed.

A casting method includes preparing a thin shell mold which is sintered and placed in a box. Sands are buried in the box to encompass the thin shell mold. The pressure chamber is depressurized. The casting material is filled into the thin shell mold, such that the thin shell mold is disposed at a vacuum state. Then, the negative pressure of the pressure chamber is released. Then, the pressure chamber is pressurized, to form a pressure difference which presses the casting material to flow into the thin shell mold, thereby finishing the casting work. The temperature of the casting material is reduced, and the pressure in the pressure chamber is increased. Then, the casting material is cooled to form a casting product. Then, the thin shell mold is broken, and the casting product is removed.

A casting method includes preparing a thin shell mold which is sintered and placed in a box. Sands are buried in the box to encompass the thin shell mold. The pressure chamber is depressurized. The casting material is filled into the thin shell mold, such that the thin shell mold is disposed at a vacuum state. Then, the negative pressure of the pressure chamber is released. Then, the pressure chamber is pressurized, to form a pressure difference which presses the casting material to flow into the thin shell mold, thereby finishing the casting work. The temperature of the casting material is reduced, and the pressure in the pressure chamber is increased. Then, the casting material is cooled to form a casting product. Then, the thin shell mold is broken, and the casting product is removed.

A casting method includes preparing a thin shell mold which is sintered and placed in a box. Sands are buried in the box to encompass the thin shell mold. The pressure chamber is depressurized. The casting material is filled into the thin shell mold, such that the thin shell mold is disposed at a vacuum state. Then, the negative pressure of the pressure chamber is released. Then, the pressure chamber is pressurized, to form a pressure difference which presses the casting material to flow into the thin shell mold, thereby finishing the casting work. The temperature of the casting material is reduced, and the pressure in the pressure chamber is increased. Then, the casting material is cooled to form a casting product. Then, the thin shell mold is broken, and the casting product is removed.