MEC304 Flashcards
What is manufacturing?
The transformation of input materials into a useable product
What is a manufacturing process?
A piece of equipment for carrying out a manufacturing task
What is a manufacturing strategy?
A sequence of processes appropriate to turn the raw material into the finished
product, with the necessary Quality Assurance
What is a manufacturing system?
The physical representation of the strategy within an industrial environment, with
appropriate factory management (e.g production lines, batching)
What are some common inputs for manufacturing process?
Raw material, components, energy, labour and equipment
What are some common outputs for manufacturing process?
Product, data and waste
What are the drivers for selecting a manufacturing strategy?
● Material selection,
● Equipment availability, ●Operating constraints,
● Tooling costs,
● Expected volume and cost of product
What are Solidification Processes?
● Uses heat to melt the
material, then it is poured
into a mould to solidify,
● Often used to create the
initial shape of a component,
● Can be used with metals, polymers and glass,
● Can produce finished,
near-net-shape or
oversized components
What is sand casting?
● A pattern is made to the shape of the finished product
● Sand is packed into the bottom half of a
mould and the pattern is pressed on the surface
● The upper half of the mould is placed on top and fitted with pouring channels
● It is packed tightly with more sand
● The mould is split to allow the pattern to be removed
● The mould is closed and metal is poured in to fill the cavity
What is investment casting?
● A pattern is made from wax to the shape of the finished product
● The wax pattern is coated in ceramic
slurry, which is fired to form a solid mould
● During firing, the wax melts and runs out, leaving a hollow cavity
● Metal is poured in to fill the cavity
● Internal channels can be formed by placing a ceramic core in the wax
pattern at the start, which is then leached out of the metal casting
What is permanent mould casting?
● A mould (die) is machined from a
material able to withstand thermal cycling - grey cast iron is often used
● Molten metal is poured into the mould and allowed to cool
● The mould is opened and the casting is removed
● The mould can be reused for multiple castings, although it will
require regular maintenance
What is the equation for ts solidification time?
CHVORINOVʼS RULE
ts = B (V / A)^n
B mould constant
V mould volume
A area of heat extraction
n a constant 1.5 - 2.0
What is injection moulding?
● A polymer is heated until is molten and free flowing (~300°C)
● It is injected, under high pressure (300-1500 bar), into a mould (die) where it solidifies
● Geometric accuracy is limited by the draft angle, added to allow the part
to be removed from the die
● Normally produces finished shape
components
What are Forming Processes?
● Use plastic deformation to achieve a change in shape, without loss of
material
● Can be used to create the initial shape of a component
● Hot forming achieves a significant change in shape, with the heat
making the material easier to work
● Cold forming makes the material stronger through strain hardening
and can achieve tighter tolerances
What is rolling and what products are made from this?
● The material is forced between pairs of rollers, which compress it to
reduce its thickness
● Multiple stages may be necessary to achieve the final shape
● Thin sheets (aluminium foil) to rail tracks and
structural beams
What is the power required equation for a 2-roller set-up?
P = 2 π N F L
P power
F roller force
N roller spindle speed(rps)
L contact length
What is forging?
● The material is compressed between
two halves of a die, either gradually or through impact
● Forging is fast, produces less waste than machining and often produces a
stronger product
● Used for high-strength structural components (shafts, discs and rings)
● Die design and manufacture is highly
critical as the die
What is extrusion & wire/bar drawing?
● Extrusion & drawing force material to
flow through a die opening to produce a defined cross-sectional
shape
● In extrusion, the unshaped material is
pushed into the die
● In wire/bar drawing, the shaped material is pulled from the die
● Used to produce wire, but can also be used for more complex shapes
What is Subtractive Manufacturing?
The process of removing unwanted material from a workpiece to achieve a change in shape
What is turning?
Turning uses a single cutting edge against a rotating workpiece to
achieve a cylindrical shape
What is drilling?
Drilling uses a rotating tool with two cutting edges to create a
round hole
What is milling?
Milling uses a rotating tool with multiple cutting edges to create
smooth surfaces
What is cutting speed?
Speed at which tool
travels relative to workpiece
What is feed rate?
Amount of material
removed per revolution
Tm = L / fr
