Metal processes
Die Casting
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Large quantities of quality castings are required in industry,
the moulds(dies) need to be permanent.
Alloy steel moulds are costly to produce because they are
made in sections fro easy removal
High operating costs involved make this process
economically viable for high volume mass production where
accuracy of shape, size and surface finish is essential.
Materials used in this process include low melting
temperature allows, lead, zinc, aluminium and brass alloys.
Identifying features: Section hair lines, ejector pin marks,
flashes caused by leakages left on internal surfaces, sprue
and runner marks
Die Casting
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A measure of molten
metal is poured into the
charge chamber
An injection piston then
forces the metal into a
water cooled die through
a system of sprues and
runners
The metal solidifies
rapidly and the casting is
removed, complete with
its sprues and runners.
Pressure Die Casting
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“hot” chamber and “cold”
chamber processes are used
Both processes have molten
metal that is forced into a metal
die by a hydraulic ram
Thin sections and complex
shapes with fine detail are
possible.
Sand Casting
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Most frequently used metal casting process
‘Green’ found sand (describing damp quality that bonds sand
together) is a blend of silica grains, clay and water.
Oil-bound sand gives excellent results but is relatively expensive
and difficult to reconstitute.
Element of waste involved as sand that is in contact with hot metal
will burn which need to be scraped out and disposed of.
Quality of casting depends on quality of pattern that is normally
made from wood.
Pattern requires radiused corners, drafted sided and good surface
finish.
Material: Iron, aluminium and non ferrous alloys.
Features: Complex 3D components, Draft angles, rounded corners
and strengthening webs.
Sand Casting
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Place pattern centrally in drag
Pack sand around pattern
Turn drag over and attach cope
Insert sprue pins and pack sand
around
Remove sprue pins
Split moulding box and cut gates
Remove pattern to leave a cavity
Reassemble cope so mould is
ready to recieve molten metal
Pour the molten metal into runner.
Melt fills mould and exits, along
with any gases, via the riser.
Press Forming
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Involves squeezing sheet metal between two matched metal moulds
(dies)
Gives a very strong, shell like structure.
One die is mirror image of the other apart from an allowance for
the thickness of the material.
Machining of these dies is a specialised skill.
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Can be complicated and difficult hence time consuming
Very expensive to produce.
Rubber blocks can be used instead of one of the dies making it
more straightforward applicaitons.
Material: sheet metals of various steels, aluminium alloys, brass and
copper
Features: Different operations can be identified of ribs, piercing
Press Forming
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A blank is cut to the
required size
The blank is placed in a
press
Product id formed using
immense force.
 1000tones
are required
to manipulate 3.5mm
thick steel plate
Piercing and blanking
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Piercing and blanking is essentially the same process.
Involves the stamping of shapes out of sheet metal of
metal strip
Differences depend on which bit of metal is to be kept
Piercing is when a shaped hole is made in the metal
 Blanking is when a shape is stamped out of metal then used.
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Material: most types of metals can be used. Metal is
normally annealed to minimize risk of fracture or
tearing.
Features: sheared surface will show 2 distinct areas of
deformation and fracture.
Piercing and blanking
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Piercing: the punch and die shown.
Note how the punch firs into the die
but does not enter it. Accurate
alignment of the two is essential.
Blanking: main components used in
mass production are a punch, a die
and a stripper plate. The plate
prevents the metal “riding up” the die
on its upward travel. The die is
attached to the main press by means
of a bolster plate. Punch is attached
to a movable ram.
Drop forging
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Industrial process used in the production of high
quality, strong metal components or products.
Accurate to produce numerous objects by using a
specialised shaped die to control flow of metal
 Highly
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skilled craftsman eliminated.
Material: most metal in allow form, alloy steel and
copper most common
Features: flashes, die parting lines
Drop forging
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Hot metal billet placed
between dies
Metal forced into cavity
using power driven
hammer.
Excess metal squeezed out
forming a flashing around
parting line of 2 dies.
Once complete flash is
removed using a trimming
die.