Manufacturing Techniques

Question 1

Name 2 single use/disposable casting techniques

Answer 1

sand casting
investment casting

Question 2

Name some casting defects

Answer 2

Liquid metals containing gas cause porous end products
metal can contain oxides
misruns/cold shuts - when metal solidifies before mould is full

Question 3

Why is sand casting used

Answer 3

low cost
versatile
small upper limit in terms of size and weight
can cast complex shapes
short lead time
mould is cheap to make from wax, wood or plastic pattern

Question 4

Common problems in sand casting

Answer 4

erosion - metal can be poured in too fast and sand can end up in the cast
penetrations - if molten material is too viscous it can flow into voids of the mould
rough surface and relatively high levels or porosity an low dimensional accuracy

Question 5

applications of sand casting and main material used

Answer 5

cylinder heads
landing gear
mainly used with alloys

Question 6

batch size of investment casting

Answer 6

10-10,000

Question 7

benefits of investment casting

Answer 7

good surface finish
can produce complex shapes
no parting line
can be used with almost any metal

Question 8

drawbacks of investment casting

Answer 8

expensive pattern and mould
high labour costs
size limitations
high lead time
single use
slurry build up in moulds

Question 9

Name 4 permanent casting methods

Answer 9

pressure casting
slush casting
die casting
centrifuge casting

Question 10

pressure casting advantages, drawbacks and minimum batch size

Answer 10

clean finish, no oxidation
expensive, long set up time
minimum batch size of 1000

Question 11

slush casting benefits and drawbacks

Answer 11

hollow cast, good external detail
wall thickness can vary

Question 12

what are the 2 types of die casting

Answer 12

hot chamber - lower melting point, non-corrosive metals
cold chamber - metal is melted separately, high melting point & corrosive alloys

Question 13

die casting advantages, drawbacks and minimum batch size

Answer 13

fast cycle times, thin sections
expensive equipment, small components produced (under 10kg)
minimum batch size of 10,000

Question 14

2 types of centrifugal casting

Answer 14

true centrifugal and semi centrifugal

Question 15

continuous casting advantages and drawbacks

Answer 15

very high volume
very basic shapes
only uses steel
post processing required since shapes are so basic

Question 16

continuous casting shapes

Answer 16

bloom
billet
rounds

Question 17

why are fluxes added to moulds

Answer 17

protect steel from oxidation

Question 18

defects of continuous casting

Answer 18

longitudinal crack
sub-surface cracks
thermal shrinking
sticker breakouts

Question 19

common applications of powder metallurgy

Answer 19

oil impregnated bearings
cutting tools
metal filters

Question 20

common powder metallurgy materials

Answer 20

iron, copper, tin, nickel, titanium

Question 21

limitations of powder metallurgy

Answer 21

typically lower strength
restricted to relatively small, light parts
expensive equipment

Question 22

what is extrusion used to manufacture

Answer 22

railings, sliding doors, window frames, tubing, brackets, gears, hangers

Question 23

materials used for extrusion

Answer 23

copper, aluminium, steel and lead

Question 24

defects of extrusion

Answer 24

cracking
centre cracking
piping

Question 25

what is punching used for

Answer 25

improve edge quality or create holes in sheet metal

Question 26

bending applications

Answer 26

car bodies, paper clips

Question 27

what is spring back

Answer 27

the material trying to return to its original shape so will straighten a bit once it has been bent

Question 28

what shapes are made with extrusion

Answer 28

pipes, rods, pellets

Question 29

thermoplastic mould temperature

Answer 29

90

Question 30

thermoset mould temperature

Answer 30

200

Question 31

welding process

Answer 31

permanent joining of two materials, usually by coalescence - bonding of the molecules of both metals

Question 32

what are tac welds used for

Answer 32

small welds to hold the join at the same angle before a full weld is carried out

Question 33

what is the fusion zone

Answer 33

the area that has been melted and solidified

Question 34

what is the heat affected zone

Answer 34

next to the fusion zone where there are changes in the microstructure but doesn't melt

Question 35

forms of flux

Answer 35

powder, paste, coated filler rod

Question 36

flux function

Answer 36

produces gas shield, chemically cleans base metal and removes oxides, removes slag

Question 37

advantages of welding

Answer 37

extremely strong joint distributed force light weight joint

Question 38

limitations of welding

Answer 38

high energy requirements limited to certain metals similar metals must be used permanent joints residual stresses and distorsion HAZ expensive

Question 39

most common resistance welding process

Answer 39

resistance spot welding

Question 40

resistance welding advantages and limitations

Answer 40

no electrons required, no flux, easy and fast complex and expensive equipment, electrode wear

Question 41

resistance welding applications

Answer 41

sheet metal fabrications, automotive body assembly

Question 42

diffusion welding advantages and application

Answer 42

can join different metals titanium welding in aerospace

Question 43

brazing filler metal melting point

Answer 43

>450 degrees celcius

Question 44

does brazing require a flux

Answer 44

yes - to prevent oxidation and clean base metal

Question 45

how is filler metal drawn into gap

Answer 45

capillary action - uniform gap and clean surfaces

Question 46

why is a welding agent used

Answer 46

reduce surface tension of the molten filler metal enables it to spread across the surface of the base metal

Question 47

what is the most common material used for sheet metal forming

Answer 47

low carbon steel

Question 48

brazing disadvantages

Answer 48

not suitable for high temperature operating conditions not as strong as welding (but still strong) more sustainable to corrosion tighter part tolerance required to promote capillary action

Question 49

how can you improve brazing joint strength

Answer 49

increase the contact area

Question 50

what is the filler metal melting temperature

Answer 50

<450 degrees celcius

Question 51

advantages, disadvantages and applications of soldering

Answer 51

cheap, quick, no HAZ, no distortion limited joint strength, low temp applications electronics, plumbing, automotive radiators

Question 52

name mechanical fasteners

Answer 52

stapling seaming crimping snap in fasteners

Question 53

advantages and considerations of mechanical fasteners

Answer 53

easy to manufacture, easy to assemble and disassemble, movable joints, low cost temporary joint, what materials are being joined, weight limitations, cost, appearance, dimensions

Question 54

adhesives industries

Answer 54

aerospace, automotive, home appliances, building products

Question 55

adhesive advantages and limitations

Answer 55

strong sealed bonds, distributed loads, thin components, low temperatures >200, no distortion, corrosion resistant limited range of temps, long bonding time, surface prep vital

Question 56

what is subtractive manufacturing

Answer 56

parts made by removing material by chipping away from a bulk

Question 57

additive manufacturing

Answer 57

parts made from small building blocks e.g. inkjet printing

Question 58

advantages and disadvantages of additive manufacturing

Answer 58

more efficient energy use, waste reduced, huge design freedom slow production, expensive

Question 59

inkjet printing advantages and disadvantages

Answer 59

stencil can be reused, stencil defines final print contamination from earlier prints, incomplete ink transfer, one ink at a time

Question 60

what is the rake angle

Answer 60

angle of the cutting tool to the vertical

Question 61

what is the relief angle

Answer 61

the angle of the cutting tool to the horizontal

Question 62

up milling description

Answer 62

feed direction is traveling in the opposite direction to the tool direction

Question 63

advantages and disadvantages of up milling

Answer 63

backlash isn't an issue surface finish is impared, suited for older machines

Question 64

down milling advantages

Answer 64

better surface finish, better for modern machines

Question 65

which teeth go into a material first when broaching

Answer 65

roughing teeth then finishing teeth

Question 66

abrasive machining advantages and applications

Answer 66

high dimensional accuracy, excellent surface finish, can be applied to hard, brittle materials ball bearings, pistons, valves, gears

Question 67

most common abrasive machining process

Answer 67

grinding

Question 68

what material does honing use

Answer 68

abrasive stones

Question 69

what material does lapping use

Answer 69

leather