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Case Study #1 - Vectrix Corp - "We were able to have 'machined' castings in three weeks." View Study
Case Study #2 - Intuitive Surgical - "Award Winning Medical Robot utilizes castings to reduce cost." View Study
PRECISION SAND CASTING
General Foundry Service's niche is making "Thin-Walled", "Smooth
Surface" Precision Sand Castings that delight our customers.
Precision Sand Casting is a term we use for our proprietary
method of the "green-sand" molding process. It is a process where our
proprietary mixture of sand, clay, and water is packed around a "Positive"
(typically a Matchplate) by hand, with power tools, or in a pneumatic machine,
which will exert a compressive force to pack the grains of sand and clay close
together to form each mold half.
The term "green-sand" implies that the sand binder is not cured by heating
or chemical reactions.
Read our article on: Precision Sand Castings Vs. V-Process Castings.
Some foundries make tooling from patterns split into two "halves",
which are attached to opposite sides of a flat board.
In order to ensure the tooling you purchase from us will last the life
of your program, we will produce a "cast" aluminum "Matchplate" from a
single pattern of your geometry.
The sprue, runner system, and gates are fastened to the plate to
form connecting channels in the sand for entry of the molten metal
into the casting cavities.
The photos on the right are of a matchplate with four "positives"
of our renowned ice cream scoops. The resulting mold will produce
four castings from each mold created from the matchplate tooling.
The pattern on the right is a fabricated wood/plastic pattern that is primed and sanded to a smooth finish.
The photo on the right illustrates a "matchplate" that is compressed
between two flask halves (the cope & drag), prepared for sand to
be poured against it to produce each half of the mold. The opposite
side of the matchplate contains the opposite side of the casting. The
impression of the matchplate will be made in the sand. The sand is
supported at the plate edges by a box-shaped flask. Interlocking tabs
align the two mold halves when they are later assembled for the pouring
Hollows and undercut surfaces in the casting are produced by cores,
also made from sand (with a resin binder), that are placed in position
before the mold is closed. An undercut surface is one from which the
pattern cannot be withdrawn in a straight line, so must be formed by a
core in the mold.
The core(s) are held in place by the core-prints,
formed in the-sand by pattern projections. When the poured metal has
solidified, the jacket, ( a fitted structural girdle that bridges the parting line
to reinforce the sand, prevent parting line runouts and distortion of the mold), is
removed and the sand falls off with the aid
of vibration, leaving the finished casting(s) ready to be sawed from
The photos on the right are from castings that have "cored" features
in each part.
Please contact General Foundry Service to discuss Precision Sand Casting and our design recommendations.
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