Lecture 2 Flashcards
1
Q
Examples of expendable mould casting
A
- sand
- investment (lost wax)
- evaporative pattern (lost foam)
2
Q
Examples of permanent mould casting
A
- gravity die
- pressure die
- centrifugal
3
Q
sand casting
A
- make cavity in sand of desired casting using pattern
- permeable: still lets gases through
- allows metal to shrink avoiding heat tears
4
Q
what are cores
A
in sand casting: core prints used to hold and align the core in the cavity
5
Q
what are chaplets
A
in sand casting: metal supports to provide extra stability to the core
6
Q
sand casting advantages:
A
- no size limit, variety of metals and shapes
- cheap moulds
7
Q
sand casting disadvantages
A
- dificult to meet exact engineering requirements e.g. tolerances
- suited to low production volumes
8
Q
sand - what type of casting?
A
permanent pattern
9
Q
investment/lost wax casting
A
- no split mould
- pattern surrounded by ceramic coating that becomes mould
10
Q
lost wax process
A
- 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
11
Q
lost wax casting advantages
A
- only method for producing precision casting of high melting point materials
- requires minimal finishing
12
Q
lost wax - what type of casting
A
expendable mould and pattren
13
Q
evaporative pattern/lost foam casting
A
- pattern made from expanded polystyrene
14
Q
what are permanent mould
A
- not broken up - designed to be removed from mould
15
Q
permanent mould advantages
A
- reusable
- good accuracy and surface finish
