Types of Molds (advantages vs. disadvantages)

Question 1

3 Types of Sand Casting

Answer 1

• Green Sand Mold
• Cold Box Mold
• No Bake Mold

Question 2

Type of Mold destroyed after each use

Answer 2

Expendable Mold

Question 3

Sand Casting Advantages

Answer 3

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

Question 4

What is Green Sand Mold

Answer 4

Refers to the mold obtaining moisture during pouring

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

Question 5

What is Cold Box Mold

Answer 5

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

Question 6

What is No-Bake Mold

Answer 6

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

• Allows for complex geometries
• Fair dimensional accuracy

Question 7

Shell Mold Casting Advantages

Answer 7

Mold Walls are smooth resulting in

• Sharper Corners
• Thinner sections
• Low resistance to flow

Question 8

Shell Mold Casting Disadvantages

Answer 8

-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

Question 9

Plaster-Mold Casting Advantages

Answer 9

Made of plaster (talc and silica flour in water)

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

Question 10

Plaster-Mold Casting Disadvantages

Answer 10

Very low permeability (traps gases)

Limited max temperature

Question 11

Ceramic Casting Advantages

Answer 11

Same as Plaster mold except uses ceramic

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

Question 12

Ceramic Casting Disadvantages

Answer 12

-Very expensive

Question 13

Lost Foam Process

Answer 13

Uses Polystyrene pattern that evaporates among contact with molten metal

Question 14

Lost Foam Advantages

Answer 14

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

Question 15

Lost Wax Process

Answer 15

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

Question 16

Lost Wax Advantages

Answer 16

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

Question 17

Lost Wax Disadvantages

Answer 17

• Only for small parts

- Complicated and Expensive

Question 18

Permanent Mold Castings

Answer 18

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

Question 19

2 types of Die Castings

Answer 19

Hot-Chamber

Cold Chamber

Question 20

Hot-Chamber

Answer 20

Molten Metal is directly attached to machine

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

Question 21

Cold-Chamber

Answer 21

Metal is brought in from an external source

• Slower Production rate
• Can use higher melting point alloys

Question 22

3 Types of centrifugal casting

Answer 22

True Centrifugal
Semi Centrifugal
Centrifuging

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

Question 23

True Centrifugal Casting

Answer 23

• 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

Question 24

Semi Centrifugal casting

Answer 24

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

Question 25

Centrifuging

Answer 25

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