V-shape, also known as vacuum casting, due to take English Vacuum (vacuum) term of the prefix "V" is named. It is different from the traditional sand casting of the biggest advantages is the use of adhesives, V method is the use of plastic film sealed casting sand box, type out by the vacuum pumping system within the air pressure difference between inside and outside the mold, so dry sand compaction, formation of need cavity, the lower core, and boxes, vacuum casting solidification of the casting, vacuum lifting, followed by collapsing sand castings obtained.