Types of Molds (advantages vs. disadvantages) Flashcards

(25 cards)

1
Q

3 Types of Sand Casting

A
  • Green Sand Mold
  • Cold Box Mold
  • No Bake Mold
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2
Q

Type of Mold destroyed after each use

A

Expendable Mold

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3
Q

Sand Casting Advantages

A
  • Most Widely Used
  • Inexpensive
  • resistant to elevated temps
  • good permeability to allow gases to escape
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4
Q

What is Green Sand Mold

A

Refers to the mold obtaining moisture during pouring

  • Least expensive
  • Good re-usability
  • moisture can cause defects
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5
Q

What is Cold Box Mold

A

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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6
Q

What is No-Bake Mold

A

Synthetic liquid resin is mixed with sand (bonded with no heat added)

  • Allows for complex geometries
  • Fair dimensional accuracy
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7
Q

Shell Mold Casting Advantages

A

Mold Walls are smooth resulting in

  • Sharper Corners
  • Thinner sections
  • Low resistance to flow
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8
Q

Shell Mold Casting Disadvantages

A

-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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9
Q

Plaster-Mold Casting Advantages

A

Made of plaster (talc and silica flour in water)

  • High dimensional accuracy
  • Cools slower (uniform grain structure)
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10
Q

Plaster-Mold Casting Disadvantages

A

Very low permeability (traps gases)

Limited max temperature

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11
Q

Ceramic Casting Advantages

A

Same as Plaster mold except uses ceramic

  • Suitable for High Temps
  • Good dimensional accuracy
  • Extremely high tolerances
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12
Q

Ceramic Casting Disadvantages

A

-Very expensive

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13
Q

Lost Foam Process

A

Uses Polystyrene pattern that evaporates among contact with molten metal

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14
Q

Lost Foam Advantages

A
  • Cools very fast
  • Very complex geometries can be produced
  • Flask is inexpensive
  • No removal of pattern
  • easily automated
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15
Q

Lost Wax Process

A

Wax patterns can be joined into 1 mold making a ‘tree’

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16
Q

Lost Wax Advantages

A
  • Significantly increases production rate
  • Allows for extremely complex parts
  • Good surface finish
17
Q

Lost Wax Disadvantages

A
  • Only for small parts

- Complicated and Expensive

18
Q

Permanent Mold Castings

A
  • Higher initial set up costs (bad for small production runs)
  • Once set up, extremely economical for large runs
  • Highly automated (less rejects)
19
Q

2 types of Die Castings

A

Hot-Chamber

Cold Chamber

20
Q

Hot-Chamber

A

Molten Metal is directly attached to machine

  • High velocity of productivity
  • Thermal damage occurs because continuously submerged in high temp alloys
21
Q

Cold-Chamber

A

Metal is brought in from an external source

  • Slower Production rate
  • Can use higher melting point alloys
22
Q

3 Types of centrifugal casting

A

True Centrifugal
Semi Centrifugal
Centrifuging

(All use internal forces caused by rotation to force Metals into cavities)

23
Q

True Centrifugal Casting

A
  • 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
24
Q

Semi Centrifugal casting

A

-Mold is filled completely with molten metal through a central sprue

25
Centrifuging
- Doesn't have rotational symmetry | - Arranged around central sprue