Types of Molds (advantages vs. disadvantages) Flashcards Preview

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Flashcards in Types of Molds (advantages vs. disadvantages) Deck (25):
1

3 Types of Sand Casting

-Green Sand Mold
-Cold Box Mold
-No Bake Mold

2

Type of Mold destroyed after each use

Expendable Mold

3

Sand Casting Advantages

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

4

What is Green Sand Mold

Refers to the mold obtaining moisture during pouring

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

5

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

6

What is No-Bake Mold

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

-Allows for complex geometries
-Fair dimensional accuracy

7

Shell Mold Casting Advantages

Mold Walls are smooth resulting in

-Sharper Corners
-Thinner sections
-Low resistance to flow

8

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

9

Plaster-Mold Casting Advantages

Made of plaster (talc and silica flour in water)

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

10

Plaster-Mold Casting Disadvantages

Very low permeability (traps gases)
Limited max temperature

11

Ceramic Casting Advantages

Same as Plaster mold except uses ceramic

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

12

Ceramic Casting Disadvantages

-Very expensive

13

Lost Foam Process

Uses Polystyrene pattern that evaporates among contact with molten metal

14

Lost Foam Advantages

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

15

Lost Wax Process

Wax patterns can be joined into 1 mold making a 'tree'

16

Lost Wax Advantages

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

17

Lost Wax Disadvantages

-Only for small parts
-Complicated and Expensive

18

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)

19

2 types of Die Castings

Hot-Chamber
Cold Chamber

20

Hot-Chamber

Molten Metal is directly attached to machine

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

21

Cold-Chamber

Metal is brought in from an external source

-Slower Production rate
-Can use higher melting point alloys

22

3 Types of centrifugal casting

True Centrifugal
Semi Centrifugal
Centrifuging

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

23

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

24

Semi Centrifugal casting

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

25

Centrifuging

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