Lecture 2

Question 1

Examples of expendable mould casting

Answer 1

• sand
• investment (lost wax)
• evaporative pattern (lost foam)

Question 2

Examples of permanent mould casting

Answer 2

• gravity die
• pressure die
• centrifugal

Question 3

sand casting

Answer 3

• make cavity in sand of desired casting using pattern
• permeable: still lets gases through
• allows metal to shrink avoiding heat tears

Question 4

what are cores

Answer 4

in sand casting: core prints used to hold and align the core in the cavity

Question 5

what are chaplets

Answer 5

in sand casting: metal supports to provide extra stability to the core

Question 6

sand casting advantages:

Answer 6

• no size limit, variety of metals and shapes

- cheap moulds

Question 7

sand casting disadvantages

Answer 7

• dificult to meet exact engineering requirements e.g. tolerances
• suited to low production volumes

Question 8

sand - what type of casting?

Answer 8

permanent pattern

Question 9

investment/lost wax casting

Answer 9

• no split mould

- pattern surrounded by ceramic coating that becomes mould

Question 10

lost wax process

Answer 10

• produce master pattern, die and wax patterns
• assemble on tree and coat
• allow to harden and melt out wax pattern
• pour molten metal into mould and let it solidify

Question 11

lost wax casting advantages

Answer 11

• only method for producing precision casting of high melting point materials
• requires minimal finishing

Question 12

lost wax - what type of casting

Answer 12

expendable mould and pattren

Question 13

evaporative pattern/lost foam casting

Answer 13

• pattern made from expanded polystyrene

Question 14

what are permanent mould

Answer 14

• not broken up - designed to be removed from mould

Question 15

permanent mould advantages

Answer 15

• reusable

- good accuracy and surface finish

Question 16

permanent mould disadvantages

Answer 16

• suited to lower melting point materials

- wear of mould

Question 17

gravity die casting

Answer 17

• no external force applied other than atmospheric pressure

- involves feeder

Question 18

gravity die advantages

Answer 18

long die life, minimal machining

Question 19

gravity die disavantages

Answer 19

slow production rates and limited complexity

Question 20

gravity die - what type of casting

Answer 20

permanent mould

Question 21

pressure die casting

Answer 21

forces molten metal into mould under high pressure

Question 22

pressure die casting process

Answer 22

• lube and lock dies
• molten metal forced into cavity
• held under pressure until solidification

Question 23

hot chamber process

Answer 23

in pressure die casting:

• metal maintained molten
• some metal forced through shaped channel

Question 24

cold chamber process

Answer 24

in pressure die casting:

• molten metal poured into injection cylinder
• cylinder not heated

Question 25

What is misrun

Answer 25

when molten metal solidifies before it fills the mould