V method casting and lost foam casting are also called negative pressure casting, named after the initial "V" of the word "Vacuum" in English. The biggest advantage of it different from traditional sand casting is that it does not use adhesives. V method casting uses plastic film to seal the sand box and extracts the air inside the mold by a vacuum exhaust system. There is a pressure difference between the inside and outside of the mold, which makes the dry sand compact and form For the required cavity, the casting is solidified by core lowering, box mixing, pouring and vacuuming, the negative pressure is relieved, and the casting sand is collapsed to obtain the casting.
Compared with traditional sand casting, V method casting and lost foam casting have the following advantages:
First, because it adopts negative pressure pouring castings, there are few sand holes, high product density, smooth surface, clear outline, and accurate size;
Second, energy-saving, high-efficiency and clean production. The use of V method and lost foam technology can make dry sand repeatedly used without drying, and reduce coal consumption. However, due to long-term vacuum machine operation, power consumption is slightly increased, but dust is greatly reduced, human capital is saved, and foundry work It is more effective, saves labor and greatly reduces labor intensity, less harmful gases in the pouring process, and truly environmentally-friendly production.
The key point of V method casting production is to select a vacuum pumping system. When selecting a vacuum pumping system, first determine the capacity of the vacuum pump, mainly considering the following factors:
1. The size and quantity of sand boxes that need to work under vacuum at the same time;
2. The number of molds poured at the same time;
3. The size and shape of pouring;
4. The air permeability of the mold surface close to the film controls the amount of air entering the mold through the cracks in the plastic film. Therefore, it is necessary to use a small amount of mold coating when pouring, which helps to vacuum The machine provides an "auxiliary sealing layer".