The V-method casting and the lost foam casting are also known as vacuum casting. They get their name from the initial letter "V" of the English word "Vacuum" (vacuum). Compared to traditional sand casting, the advantage of V-method casting is that no binder is used. In V-method casting, a plastic film is used to seal the sand box, and a vacuum pumping system is employed to evacuate the air inside the mold. There is a pressure difference between the inside and outside of the mold, which causes the dry sand to become compacted, forming the desired cavity. After core removal, box closing, pouring, and vacuum extraction to remove the negative pressure, the casting solidifies and the sand structure collapses, resulting in the formation of the casting. 

The casting industry has developed a new casting technique - the V-method casting. The V-method casting is a vacuum-sealed molding process. Its principle is to seal the sand box with a plastic film and use a vacuum pump to remove the air inside the mold. This creates a pressure difference between the inside and outside of the mold, causing the dry sand to become compacted, thus forming the desired cavity. The advantage of the V-method casting over traditional sand casting is that it does not use binders, thereby reducing the sand processing work. Moreover, the labor required for mold and casting sand cleaning is significantly reduced, and the recovery rate of old sand is high. 

The castings produced by the V-method casting process have excellent quality, smooth surfaces, clear contours, accurate dimensions, and uniform hardness. They effectively extend the service life of the castings and have been highly praised by users, becoming the new favorite in the industry. 

The V-method casting and the lost foam casting have the following advantages compared with the traditional sand casting: 

Firstly, because it uses negative pressure casting, the casting has fewer sand holes, higher product density, smoother surface, clear contours, and accurate dimensions. 

Secondly, energy-saving, efficient and clean production. By using the V method and the lost mold technology, the dry sand can be reused repeatedly. There is no need for mold drying, coal consumption is reduced, but due to the long-term operation of the vacuum machine, the power consumption slightly increases. However, it greatly reduces dust, saves human capital, makes the casting work more efficient, saves labor and greatly reduces labor intensity. During the pouring process, there is less harmful gas, truly achieving environmental protection production. 

The key point in the V method production lies in selecting the vacuum pumping system. When choosing the vacuum pumping system, the capacity of the vacuum pump should be determined first. The main factors to consider are: 

The size and quantity of the sandboxes that need to work under vacuum simultaneously. 

2. The number of casting molds that are cast simultaneously; 

3. The size and shape of the casting; 

4. The permeability of the casting surface directly adjacent to the film controls the amount of air that enters the casting through the cracks in the plastic film. Therefore, during the pouring process, it is necessary to apply a small amount of casting coating, which helps to provide an "auxiliary sealing layer" for the vacuum machine.