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Manufacturing Processes - Vacuum ("V") Process Molding


Manufacturing: Metal Casting

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Metal Casting Techniques - Vacuum ("V") Process Molding

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.

Because the V-Process uses clean, dry unbonded sand, you can forget about mullers and mixers, and costly sand reclamation and reconditioning equipment. Most V-Process users require only sand cooling and transportation, dust collection and simple screening to remove tramp metals.

Molding equipment is simple too. It can be limited to as few as five items (a vacuum system, Film heater, vibrating table, pattern carrier and flasks) or automated for higher production. There is no need for heavy, noisy jolt squeeze equipment, ramming of slingers.

The molding media is clean and dry therefore shakeout equipment is usually nothing more than a grate to allow the sand to flow away from the casting and back into the sand system. Fume and odor control is unnecessary in most applications.


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.


  • Superb finishes.
  • Good dimensional accuracy.
  • No defects from gas holes.
  • All sizes and shapes of castings are possible from thin walls to thick sections, or from castings weighing ounces to several tons. Sand thermal conductivity is lower and metal fluidity is improved. Solidification time is slower. In addition, zero draft designs are common, and can reduce clean up and rough machining operations.
  • Most ferrous / non-ferrous metals can be used.
  • Low operating cost - You not only save on the cost of sand binders but all of the cost of sand mixing, testing and disposal/ reclamation. Even pattern life is extended because the sand never touches the pattern and it is never subjected to the rigors of a conventional molding machine. Finally, V-Process produces castings with fewer imperfections and less scrap.


  • The V-process requires plated pattern equipment.


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