Casting Processes

Question 1

one time use moulds

Answer 1

green sand moulds
CO2 moulds
investment casting

Question 2

multiple use moulds

Answer 2

pressure die casting

Question 3

Allowance for sand casting should be included for

Answer 3

shrinkage, machining, pattern taper and core prints

Question 4

Sand moulding requirements

Answer 4

sufficiently refractory (withstand high temp. of molten metal)
sufficiently permeable (allow the escape of gases)
sufficient strength (prevent breaking of mould)
should not harden excessively (to knock out easily)

Question 5

component needed to produce hollow green sand casting

Answer 5

cores

Question 6

5 parts of the gating system and its purpose

Answer 6

Sprue: allow molten metal to descend from surface of mould to the runner
Runner: allow molten metal to flow to mould cavities through gates
Gates: allow molten metal to flow from runner to cavities
Riser: feed shrinkage during solidification
Vents: increase permeability of sand

Question 7

Advantages of sand casting

Answer 7

great complexity for large range of metals and alloys

cheap to use when small numbers of casting needed

Question 8

disadvantages of sand casting

Answer 8

dimension accuracy is worse than other processes
surface finish is poor
cast components are weak and brittle

Question 9

Purpose of CO2 casting process

Answer 9

Making strong sand cores without baking

Question 10

advantages of CO2 casting process

Answer 10

makes the sand mould very hard

Question 11

limitations of CO2 casting process

Answer 11

cured moulds are not easily broken up

sand is seldom recycled

Question 12

Steps of investment casting

Answer 12

1) Produce wax pattern
2) Assemble wax pattern
3) Shell Making
4) Dewaxing & Firing
5) Casting
6) Knockout
7) Finishing

Question 13

2 method of investment casting and its applications

Answer 13

Ceramic shell mould: turbine blades, implants (large components)

Block mould: small items, gold jewellry

Question 14

purpose of fine primary refractory layer in investment casting is to

Answer 14

provide good surface finish to the casting

Question 15

Advantages of investment casting

Answer 15

complex parts can be casted
can use wide range of alloys (high mp alloys)
close dimensional tolerance

Question 16

Limitations of investment casting

Answer 16

process is time consuming

set up cost for process is high

Question 17

2 types of die casting processes and the types of alloys use for each process

Answer 17

Hot chamber die casting: Zn, Pb, Sn alloys

Cold chamber die casting: Al, Mg, Cu alloys

Question 18

Hot chamber die casting disadvantage

Answer 18

high risk of air entrpament

Question 19

advantages of die casting process

Answer 19

more complex shape can be made than by sand casting
production rate is high
dies can be reused multiple times without changing its dimensions
excellent dimensional accuracy and surface finishing

Question 20

ingredients to make mould for sand casting is

Answer 20

sand, water, bentonite

Question 21

ingredients to make mould in carbon dioxide casting process

Answer 21

sand and solution of sodium silicate

Question 22

describe the process on die casting

Answer 22

injection of molten metal at high speed into the steel mould