EG-182 Manufacturing technology

year 1 summer exams

what does manufacturing do?

It transforms raw materials into useful, functional items through controlled processes.

Technological definition

Application of physical and chemical processes to transform materials into products

Technological key idea

manufacturing adds value by changing material form or properties

Economic definition

Sequence of operations that add value to materials by turning them into products customers want

Economic key idea

Manufacturing adds value and utility making materials more useful and desirable

What is the share of UK output (GVA) from manufacturing?

8.8%

What is the share of employment in manufacturing?

7.9%

What is the global ranking (2022) of the UK in manufacturing?

dropped to 12th

What is the historical output in USD (2023) of the UK?

$279-284 billion

What are primary industries?

Extract raw, natural materials

What are secondary industries?

Process raw materials and create products

What are tertiary industries?

provide a service (probably using these products directly/ indirectly

What two main categories can final products made by manufacturing industries be grouped into?

Consumer good and capital goods

What are consumer goods?

bought by individuals for personal use (use it)

What are capital goods?

Bought by companies to make products or deliver services (use it to make something else)

Production quantity definition

the number of units produced annually of a given product type

Product variety definition

the number of different types of products made

What are the three ranges of production quantity?

• Low production

• Medium production

• High production

How many units per year is low production?

up to 100

How many units a year is medium production?

100 to 10,000

How many units per year is high production?

10,000 to millions

What are the two basic types of manufacturing operations?

• Processing operations

• Assembly operations

What is processing operations?

transforms a work material from one state of completion to a more advances state that is closer to the final desired product - usuals performed on discrete work parts

What are assembly operations?

joins two or more components to create a new entity, called an assembly, subassembly, or other term.

When is casting most suitable?

When:

• Geometry is complex

• Internal features are required

• Production volumes are medium to high

When might casting not be ideal?

When:

• Very tight tolerances are required

• Surface finish is critical

• Production volume is very low

Casting of metals definition

Process in which molten metal flows by gravity or other force into a mould where it solidifies in the shape of the mould cavity

Steps of casting

• Melt the metal

• Pour it into a mould

• Let it freeze

What is - Can create complex part geometries - an advantage of?

Casting

What is- Can create both external and internal shapes- an advantage of?

Casting

What is -some casting processes are net shape; other are near net shape- an advantage off?

Casting

What is net shape?

No further shaping/ machining necessary

What is - Can produce very large parts- an advantage of?

Casting

What is- some casting methods are suited to mass production- an advantage of?

Casting

What is- limitations on mechanical properties- a disadvantage off?

Casting

What is- Poor dimensional accuracy and surface finish for some processes- a disadvantage off?

Casting

What is- safety hazards to workers due to hot molten metals- a disadvantage off?

Casting

What is environmental problems a disadvantage off?

Casting

The mould in Casting:

Contains the cavity whose geometry determines part shape

• Actual size and shape of cavity must be slightly enlarged to allow for shrinkage of metal during solidification and cooling

• Moulds are made of a variety of materials, including sand, plaster, ceramic and metal

What type of casting mould is this? give description

open mould

What type of casting mould is this? give description

closed mould for more complex mould geometry

with gating system leading into the cavity

What are the two categories of casting processes?

• Expendable mould processes

• Permanent mould processes

What are Permanent mould processes in casting?

Use a permanent mould which can be used to produce many casting

• Made of metal (~or, less commonly, a ceramic refractory material)

What are Expendable mould processes in casting?

Use an expendable mould which must be destroyed to remove casting

• Mould materials; sand, plaster and similar materials, plus binders

What are the advantages and disadvantages of an expendable mould?

• mould is sacrificed to

  remove part

• Advantage: more complex shapes possible

• Disadvantages: production rates often limited by the

  time to make mould rather than casting itself

What are the advantages and disadvantages of a permanent mould?

mould is made of metal

and can be used to make many castings

• Advantage: higher production rates, more economic

• Disadvantage: geometries limited by need to open

mould

Why are most commercial castings made of alloys rather than pure metals?

• Alloys are generally easier to cast, and properties of product

are better

• Cast iron is most popular; tonnage exceeds that of all other

metals combined

What can casting alloys be classified as?

• Ferrous

• Non-ferrous

What are the advantages and disadvantages of steel?

Advantages: Highly attractive mechanical properties

Disadvantages: Steel readily oxides at pouring temp, must be isolated from air and have poor fluidity

What are the advantages and disadvantages of cast iron?

Advantages:

• Attractive mechanical properties, lower pouring temp than steel

• Most widely used material

Disadvantages:

• Higher pouring temp than non- ferrous materials

What are the advantages and disadvantages of copper alloys (brass, bronze)?

Advantages:

• Corrosion resistance

• Attractive appearance

Disadvantages

• High cost of copper

What are the advantages and disadvantages off Aluminium?

Advantages:

• Highly castable

• Light weight

• Easy to machine

• Heat treatment can improve mechanical properties

Disadvantages:

• Mechanical properties not as great as ferrous materials

• Soft metal

What are the advantages and disadvantages of zinc?

Advantages:

• Very castable

• Low pouring temp

• Good fluidity

Disadvantages

• Low creep strength

What is the pouring temp of steel?

1600

What is the pouring temp of Cast iron?

1400

What is the pouring temp of Copper alloys (brass, bronze)?

1085

What is the pouring temp of Aluminium?

419

What steps is the total heat required a sum off?

1. Heat the solid metal

From room temperature to melting point (T0-Tm

2. Melt the metal

Energy required for solid → liquid (heat of fusion)

3. Heat the liquid metal

From melting point to pouring temperature (Tm-Tp

What is the heat required equation ?

H=pV(Cs(Tm-To)+Hf+Cl(Tp-Tm))

What is the H in the heat required equation?

total heat required to raise the temperature of the metal to the pouring temperature, J

What is the p in heat required equation?

density, g/cm3

What is the Cs in the heat required equation?

weight specific heat for the solid metal, J/g-C

What is the Tm in the heat required equation?

melting temperature of the metal, C

What is the To in the heat required equation?

starting temperature—usually ambient, C

What is the Hf in the heat required equation?

heat of fusion, J/g

What is the Cl in the heat required equation?

weight specific heat of the liquid metal, J/g-C

What is the Tp in the heat required equation?

pouring temperature, C

What is the V in the heat required equation?

volume of metal being heated, cm3

What is the heat required equations in words?

Mass × energy to heat it + melt it + get it ready to pour

Why is the heat required equation not fully realistic?

Material properties change as temperature increases

• Solid and liquid metals behave differently

• Most engineering metals are alloys, not pure metals

• Real furnaces lose heat to their surroundings

What is a cupola?

Vertical shaft furnace for continuous

melting of cast iron used in casting

What is a crucible?

Metal melted in a refractory crucible

(small batches) in casting

What is an electric arc?

Metal melted using heat from an

electric arc (mainly steel) used in casting

What is induction?

Metal melted by electromagnetic

heating with good control used in casting

What is an expendable mould process?

mould must be destroyed and reconstructed for each part

What is the sand casting production sequence?

1. Create a pattern of the final part

2. Create the mould

3. Pour the molten metal into sand mould

4. Allow time for metal to solidify

5. Break up the mould to remove casting

6. Clean and inspect casting

• Remove gating and riser system

7. Heat treatment of casting is sometimes required to improve metallurgical properties

What are the three pattern materials of sand casting?

Wood

Metal

Plastic

Why is wood used as a pattern material in sand casting?

common material because it is easy to work, but it warps

Why is metal used as a pattern material in sand casting?

more expensive to fabricate, but lasts longer

Why is plastic used as a pattern material in sand casting?

compromise between wood and metal

What must a pattern have to allow for a pattern?

A draft, gating and riser system

What type of pattern used in sand casting is this?

Solid pattern

What type of pattern used in sand casting is this?

Split pattern

What type of pattern used in sand casting is this?

Match-plate pattern

What type of pattern used in sand casting is this?

Cope and drag pattern

How is a cavity in a sand mould formed?

by packing sand around a pattern, then separating the mould into two halves

and removing the pattern

Describe the sand used for a sand mould

moist and contains a binder to maintain its shape

What must a sand mould have to have internal surfaces?

A core

What is a expendable process and how do it refer to a sand mould?

A new sand mould must be made for each part produced

What is this a mould for?

Sand casting

What requirements do a mould have to have in sand casting?

• Strength

• Permeability

• Thermal stability

• Collapsibility

• Reusability

What is the primary sand casting material used?

Foundry sand (Silica, Si02)

What is the ‘binder’ in sand casting ?

Sand is held together by a mixture of water and bonding

clay

What is the typical mix of ‘the binder’ in sand casting?

90% sand, 3% water, and 7% clay

What two halves does a mould consist of in sand casting?

• Cope = upper half of mould

• Drag = bottom half

What is the box called that contains the mould halves in sand casting?

A flask

What separates the two halves in sand casting?

the parting line

What is this diagram?

The core in sand casting

What is a chaplet in sand casting?

• Made from metal with a higher melting temperature than the casting

metal

• These chaplets bonded into the final casting – the protruding sections

are machined off

What is a gating system in sand casting?

Channel through which molten metal flows into cavity from

outside of mould