input: [Foundry Process] Vacuum ("V") Process Molding [Process] This adaptation of vacuum forming permits molds to be made out of free-flowing, dry, unbonded sand without using high-pressure squeezing, jolting, slinging or blowing as a means of compaction. The V-process is dimensionally consistent, economical, environmentally and ecologically acceptable, energy thrifty, versatile and clean. The molding medium is clean, dry, unbonded silica sand, which is consolidated through application of a vacuum or negative pressure to the body of the sand. The patterns must be mounted on plates or boards and each board is perforated with vent holes connected to a vacuum chamber behind the board. A preheated sheet of highly flexible plastic material is draped over the pattern and board. When the vacuum is applied, the sheet clings closely to the pattern contours. Each part of the molding box is furnished with its own vacuum chamber connected to a series of hollow perforated flask bars. The pattern is stripped from the mold and the two halves assembled and cast with the vacuum on. [Pros / Cons] 
output: Advantages Superb finishes. Good dimensional accuracy. No defects from gas holes. All sizes and shapes of castings are possible Most ferrous / non-ferrous metals can be used. Disadvantages The V-process requires plated pattern equipment.