Casting Techniques -
("V") Process Molding
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
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.
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
- The V-process requires
plated pattern equipment.