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Manufacturing:
Metal Casting
Metal
Casting Techniques - No-bake Molding
Since their introduction,
furan and urethane nobake binders have gained
wide acceptance for the production of molds
and cores for producing metal castings.
The advantages, regardless
of which resins are used, are based upon
control of the setting times by means of
the addition of specific amounts of catalyst.
This feature, combined with high strength
and a desirable range of hot properties
for use with various alloys, presents the
opportunity for great flexibility in mold
making.
To produce a mold using
nobake binders, the pattern is covered to
a depth of 4-5 in. with the nobake sand
mixture. The sand is allowed to set completely
and the flask is then filled with conventional
backup sand or, as the sand becomes tacky
during its setting up period, the backup
sand may be added with a sand slinger. If
ramming energy is applied before the sand
sets, the density of the sand mass at the
pattern surface is increased. This is reflected
in a better casting finish.
Advantages
- Most ferrous / non-ferrous
metals can be used.
- Adaptable to large or
small quantities
- High strength mold
- Better as-cast surfaces.
- Improved dimensional
repeatability
- Less skill and labor
required then in conventional sand molding.
- Better dimensional
control.
Disadvantages
- Sand temperatures critical.
- Patterns require additional
maintenance
- The bench life of the
sand mixture is limited.
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