Flashcards in Types of Molds (advantages vs. disadvantages) Deck (25):
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3 Types of Sand Casting
-Green Sand Mold
-Cold Box Mold
-No Bake Mold
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Type of Mold destroyed after each use
Expendable Mold
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Sand Casting Advantages
-Most Widely Used
-Inexpensive
-resistant to elevated temps
-good permeability to allow gases to escape
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What is Green Sand Mold
Refers to the mold obtaining moisture during pouring
-Least expensive
-Good re-usability
-moisture can cause defects
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What is Cold Box Mold
Uses organic or inorganic binders blended into the sand to chemically bond grains for higher mold strength
-Better dimensional accuracy than green mold
-More expensive
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What is No-Bake Mold
Synthetic liquid resin is mixed with sand (bonded with no heat added)
-Allows for complex geometries
-Fair dimensional accuracy
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Shell Mold Casting Advantages
Mold Walls are smooth resulting in
-Sharper Corners
-Thinner sections
-Low resistance to flow
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Shell Mold Casting Disadvantages
-High cost of metal patterns
BUT!
-No need for finishing or machining due to smooth finish
-several castings can be made in a single mold
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Plaster-Mold Casting Advantages
Made of plaster (talc and silica flour in water)
-High dimensional accuracy
-Cools slower (uniform grain structure)
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Plaster-Mold Casting Disadvantages
Very low permeability (traps gases)
Limited max temperature
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Ceramic Casting Advantages
Same as Plaster mold except uses ceramic
-Suitable for High Temps
-Good dimensional accuracy
-Extremely high tolerances
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Ceramic Casting Disadvantages
-Very expensive
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Lost Foam Process
Uses Polystyrene pattern that evaporates among contact with molten metal
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Lost Foam Advantages
-Cools very fast
-Very complex geometries can be produced
-Flask is inexpensive
-No removal of pattern
-easily automated
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Lost Wax Process
Wax patterns can be joined into 1 mold making a 'tree'
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Lost Wax Advantages
-Significantly increases production rate
-Allows for extremely complex parts
-Good surface finish
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Lost Wax Disadvantages
-Only for small parts
-Complicated and Expensive
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Permanent Mold Castings
-Higher initial set up costs (bad for small production runs)
-Once set up, extremely economical for large runs
-Highly automated (less rejects)
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2 types of Die Castings
Hot-Chamber
Cold Chamber
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Hot-Chamber
Molten Metal is directly attached to machine
-High velocity of productivity
-Thermal damage occurs because continuously submerged in high temp alloys
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Cold-Chamber
Metal is brought in from an external source
-Slower Production rate
-Can use higher melting point alloys
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3 Types of centrifugal casting
True Centrifugal
Semi Centrifugal
Centrifuging
(All use internal forces caused by rotation to force Metals into cavities)
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True Centrifugal Casting
-Great for hollow cylinder parts
-Impurities collect in inner region on axis of rotation
-Wall thickness is easily controlled by pouring amount
-High rate of productivity
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Semi Centrifugal casting
-Mold is filled completely with molten metal through a central sprue
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