As the name implies, sand casting uses a silica-based material,
like sand, to create a moulding surface. Sometimes manufacturers
add clay to help the sand particles bond more closely. A mold made
of sand is somewhat flexible, so theres less cracking, tearing or
other types of flaws as the liquefied material cools and
hardens.Advantages of sand casting: Lower production and
post-tooling costs The ability to cast ferrous and non-ferrous
materials The ability to create large components
Disadvantages of sand casting: Less accurate than other casting
methods Its harder to cast components with predetermined weight and
size specifications Finished items tend to have a rougher surface
finish Investment CastingInvestment casting manufacturers use a wax
pattern of a product to make a mold. They dip the wax pattern into
a refractory slurry made of materials like plaster of Paris and
silica or sillimanite and silica to form the mold. After dipping
the wax into the slurry, manufacturers heat the pattern to melt and
remove the wax, as well as harden the slurry binders. They then
pour molten metal into the mold and allow it to cool.Advantages of
investment casting: Greater accuracy Create products with precise
dimensions Create intricate, complex parts that have thin walls The
ability to cast ferrous and non-ferrous materials High-quality,
smooth finishes that require minimal machining
In sand casting, where a pattern must be prepared and used, it
is easier to produce letters and numbers by machining them into the
surface of a pattern; thus the pattern will have recessed letters.
the sand mold will then have protruding letters, as long as the
pattern is faithfully reproduced. the final part will then have
recessed letter.In investment casting, the patterns are produced
through injection molding. it is easier to include recessed
lettering in the injection molding die (instead of machining
protruding letters and pattern will have protruding letters. since
the pattern is a replica of the final part, the part will also have
protruding letter.In summary, it is generally easier to produce
recessed letters in sand casting and protruding letters in
investment casting.
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answer depends on the casting process used. In both processes,
letters are commonly machined, and it is easiest to machine
recessed letters. In sand casting, a pattern will be machined; the
recessed pattern letters will produce sand molds of protruding
letters. The parts will then have recessed letters. In investment
casting (see Section 19.3 on p. 544), the mold will likely be
machined directly; the parts will then have protruding letters.
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