Manufacturing methods

Question 1

Representation of surface finish

Answer 1

Ra = surface roughness average
low = smooth
high = rough

Question 2

Advantages and disadvantages of open die forging

Answer 2

better fatigue resistance
continuous grain flow and finer grain size
increased strength

machining required to achieve desired dimensions
not capable of forming close tolerance and high precision parts

Question 3

Advantages and disadvantages of closed die forging

Answer 3

no material limitation
better surface finish
no post machining required
internal grain structure formation increases the tightness and strength of the final product
dimensions with tight tolerances can be achieved

uneconomical for short runs due to the high cost of die production

Question 4

Sand casting

Answer 4

It involves pouring molten metal into a cavity-shaped sand mould where it solidifies. After the metal has cooled to room temperature, the sand mould is broken open to remove the casting.

Question 5

Gravity casting

Answer 5

gravity feeds molten substance into mould

quicker than sand casting
useful when making large batches
more efficient

more expensive

Question 6

Pressure casting

Answer 6

changes in grain structure as molten material is under pressure

Question 7

Cores

Answer 7

sheet metal forming
deep drawing abilities
cheap to get low batch numbers

Question 8

Laser casting

Answer 8

quick
cheap
easy
efficient

Question 9

Considerations with laser cutting

Answer 9

tiny cracks occur around the material

crack propagation can occur throughout the material

Question 10

Water-jet cutting

Answer 10

no microscopic cracks
noisier
more time consuming
better edge finishes
more expensive than laser cutting

Question 11

Advantages and disadvantages of sand casting

Answer 11

cheap
quick
simple

not suitable for dimensions with close tolerances
low mechanical properties due to the coarse grain structure as a result of the slow cooling rate

Question 12

Advantages and disadvantages of pressure casting

Answer 12

good surface finish
close dimensional accuracy
good mechanical properties
efficient in large batch production

high setup costs makes pressure casting inefficient for short runs

Question 13

Lathe

Answer 13

rotates a workpiece about an axis to perform various tasks such as cutting, sanding or turning

Question 14

Milling machine

Answer 14

shape, flat/irregular shapes

Question 15

Cutter collets

Answer 15

hold workpiece still

Question 16

Injection moulding

Answer 16

molten material injected into a cavity/mould

used to make thermoplastics, thermosets and elastomers

useful for making large batches, quick, simple components

Question 17

Common materials used in injection moulding

Answer 17

polypropylene
nylon
polyester
polycarbonate
polystyrene
ABS

Question 18

Sintering and 3D printing

Answer 18

allow complex parts to be made

low strength, expensive

Question 19

Investment casting

Answer 19

A wax pattern is manufactured for the process which is then coated with a refractory ceramic material
once the ceramic material has hardened, it takes the shape of the casting
the wax is then melted out and molten metal is poured into the cavity.
Once the metal solidifies, the metal cast is broken out

Question 20

Advantages and disadvantages of investment casting

Answer 20

allows casting of extremely complex parts
good surface finish
high dimensional accuracy with very low tolerances
efficient

complicated process and relatively expensive
limits on size