1.16 Metal Processes Flashcards
Describe the term forming
No material is removed, but materials are deformed to produce required shapes
Describe the term redistribution
The material is changed from one form to another, e.g. liquid metal poured into a mould to take a solid shape
Describe the term wastage
Material is cut away to leave the desired shape
State two features of press froming
Process form: Forming
Shapes sheet metal into 3D forms
Often used in conjunction with robots for lifting the sheet into place
Suitable for mass production or large-scale batch production
State two features of wrought iron forging
Process type: Forming
Uses wrought iron (carbon content less than 0.8%)
Can be hand or hydraulic press process
Suitable for one-off or small-batch production
State two features of cupping and deep drawing
Process form: Forming
Starts with a metal blank
Metal is stretched into shape
Used for large-scale mass or continuous production
State two features of drop forging
Process type: Forming
Use for products that need to be tough and hard
Maintains the internal grain structure which retains the strength
Hot metal billet shaped on an anvil or die and then pressed into shape and cooled
Suitable for mass production
State two features of spinning
Process form: Forming
Product may show parallel lines where the sheet has been forced onto the mandrel
Suitable for mass production or small-batch production
Describe the term addition/fabrication
Process where components and products are made by adding pieces together
State two features of sand casting
Process type: Redistribution
Labour-intensive process
Not a high-quality surface finish
Suitable for one-off or small-batch production
State two features of blending
Process type: Forming
Does not include any punching or trimming of the metal
Simple bending can be carried out in school or college workshops
Used for large-scaled batches in industry
State two features of rolling
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Process type: Forming
Hot rolling metal results in uniform mechanical properties, no deformation or stress
Surface is usually coated with carbon deposits, which must be removed using acid pickling
Cold rolling results in a material that has a tighter tolerance and better surface finish
State two features of gravity die casting
Process type: Redistribution
Lower melt point metals such as aluminium, aluminium alloys and zinc-based alloys
Relies on gravity to help the metal flow into the mould
Used for thicker mould sections
Used for very large-batch and mass production
State two features of pressure die casting (hot chamber)
Process type: Redistribution
Lower melt point metals such as aluminium, aluminium alloys and zinc-based alloys
Molten metal stored in a shot of molten metal is forced into the die
Fast process
Used for very large-batch and mass production
State two features of pressure die casting (cold chamber)
Process type: Redistribution
Lower melt point metals such as aluminium, aluminium alloys and zinc-based alloys
Molten metal ladled into shot chamber and hydraulically pushed into the chamber
Used for very large-batch and mass production
State two features of investment casting (lost wax casting)
Process type: Redistribution
Used for intricate or awkward shapes that would be difficult or impossible to mould using any other casting process
High quality, excellent finish
Wax patterns are cast from a master mould repeatable quality process
State two features of low temperature pewter casting
Process type: Redistribution
Used for school or college workshops
Can be used with a simple MDF mould
Suitable for one-off production or small batch (with aluminium moulds)
State two features of MIG welding
Process type: Addition
Uses an electrode wire
Suitable for thin-gauge metals, medium carbon steel or aluminium
Uses an inert gas such as CO2 or argon
Suitable for one-off fabrication or on an assembly line e.g. car chassis
State two features of TIG welding
Process type: Addition
Uses a filler rod
Accurate, strong welds but requires high skill levels and is quite a slow method
Uses an inert gas (argon/helium
State two features of oxy-acetylene welding
Process type: Addition
Uses a steel filler rod
Useful for quick repair jobs or in remote locations where there is no electric power supply
State the feature of spot welding
Process type: Addition
Sheet held between two copper electrodes that form a weld when the charged electrodes make contact with the metal
State the feature of soldering
Process type: Addition
Uses a filler material of a lower melting point than the metal being joined. Typically, solders are an alloy of tin and copper
State two features of brazing (hard soldering)
State two features of brazing (hard soldering)
State the feature of riveting
Process type: Addition
Riveting uses two pieces that are overlapped and drilled. The end of the shaft is then hammered over to join
State the feature of soldering
Process type: Addition
Uses a filler material of a lower melting point than the metal being joined. Typically, solders are an alloy of tin and copper
State the feature of pop riveting
Process type: Addition
Pop riveting uses a rivet gun (or riveting pliers) and a rivet and pin. Good for where the underside of the joint is inaccessible
State the feature of milling
Process type: Wastage
The milling machine can run in the x-direction (left and right horizontally), y-direction (forward and backward horizontally), and z-direction (up and down vertically) to cut slots, shape edges, or thread holes.
State the feature of turning
Process type: Wastage
The workpiece is held with a three or four jaw chuck in the headstock whilst the cutting tool moves in two axes.
State the feature of flame cutting
Process type: Wastage
Uses oxy-acetylene gas and a special flame-cutting torch to deliver a very intense and focused flame above 3,500°C.
Difficult to maintain a parallel line with high levels of tolerance
State the feature of plasma cutting
Process type: Wastage
Plasma is a super-heated ionised gas that is electrically conductive.
Plasma cutting generates a faster, cleaner cut than flame cutting
State the feature of laser cutting
Process type: Wastage
More accurate and uses less energy than plasma cutting but cannot cut the same thickness of the material
Lower-powered lasers are used in schools and colleges to cut acrylic sheets and manufacture boards such as MDF and plywood.
State the feature of punching/stamping
Process type: Wastage
Uses computer-controlled machines that stamp out sections of sheet material
Suitable for small and medium-size production runs and it is normally used for processing metals from 0.5mm to 6mm thickness.
State the three types of temporary fasteners and joining methods
Self-tapping screws
Machine screws
Nut and bolt
PRESS FORMING PROCESS 4 STEPS
1) Sheet metal is clamped over a die of the product that will determine the
final shape of the pressing.
2) A hydraulic press pushes the die into the sheet metal. Cutting blades
may be included to punch holes into the sheet and trim the excess from
the edges.
3) The hydraulic die is lowered and the pressed sheet component is removed.
4) The sheet may be placed into further press forming machines for
additional pressing, where the shape is complex.
SPINNING PROCESS
1) A former called a ‘mandrel’ is put into the chuck. The sheet metal blank
is held in place between the mandrel and the tail stock.
2) The roller tool is moved into the blank and is rotated with the mandrel.
metal stock This starts to stretch the metal over the mandrel.
3) The roller tool is moved along the mandrel as pressure is maintained
4) The roller tool is moved to the end of the mandrel, while still
maintaining contact with the blank. This finishes the shape of the
product.
5) The finished product is removed from the mandrel.
6) Excess material is trimmed off following the spirring process.
CUPPING AND DEEP DRAWING PROCESS
1) The pressing blank is clamped over a deep drawing die using a pressure
pad or clamping ring known as a retainer.
2) A hydraulic press moves the deep drawing punch to be in contact with
the blank. It then pushes the blank into the die cavity to make a cup
shape.
3) The ‘cup’ is then pressed further down through the deep drawing die to
make the desired tube shape.
DROP FORGING
PROCESS
1 A die is made from cast tool steel (which resembles a mould) and this is
secured to the top of an anvil.
2 Aram is also equipped with a die that resembles a mould.
3) The metal ‘billet’ to be forged is heated to above its recrystallisation
temperature (the temperature below the melting point shape of the metal
at which point it is possible to change the size and shape of the grains
that make up the metal). This stops the product from work hardening as
it cools, which would make it brittle.
4) Using tongs, the heated billet is placed by an operator into the
anvil die, and the hydraulic ram is brought down with force.
This makes the hot billet spread around the shape of the die.
5) The ram is lifted and the completed product removed for
cooling and finishing.
SAND CASTING PROCESS
1) A ‘pattern’ is made, usually from wood. This is a replica (sometimes
divided into two halves) of the item that will be cast, and it is placed
in the bottom of a steel box called a ‘drag’. The drag is then filled with
sand which is packed or rammed in tight around the pattern and
levelled.
2) The drag is turned over and a second box called the ‘cope’ is clamped
into position over the top of the drag. The top half of the pattern is
placed into this to mate with the bottom half of the pattern. Wooden
stakes are positioned in the cope. These will form the sprue or runner,
and riser later in the process.
3) Sand is packed into the cope around the runner, riser and pattern. A
small depression is made on the surface around the sprue to make a
pouring basin.
4) The cope and drag are separated, and the stakes and patterns are
carefully removed. Connecting channels are cut to join the sprue to the
pattern cavity, and from this to the riser. The cope and drag are then reassembled and the mould is ready for pouring to begin.
5) Small metal spikes may be inserted and removed to make vent holes.
These will allow gases from the casting process to escape.
6) The molten metal is poured into the pouring basin. It flows down
the runner, into the cavity. When the cavity is full, the molten metal
flows up the riser, indicating to the worker that the cavity is full. Once
cool, the sand is removed to reveal the casting. The runner, channels
and riser are cut off with a hack saw and the casting is ready for
machining.
INVESTMENT CASTING PROCESS
1) An exact replica or pattern of the product to be cast is made using
wax. (This might be made using a master mould machined in steel or
aluminium if the product is to be batch produced.) Where several items
are to be cast, further wax patterns might be joined together in a ‘tree’,
including a replica of the runner that will be used to pour the molten
metal in.
2) The wax pattern is dip coated with a refractory clay. It is then fired in
a kiln to bake the clay hard. The wax is burned away, leaving a hollow
clay mould.
3)Molten metal is poured into the clay mould.
4)Once the metal has filled the mould, it is allowed to cool.
5)The clay mould is then broken away, revealing the casting.
6)The runner and any connecting channels are machined off.
PEWTER CASTING METHOD
1) A mould is made from MDF, plywood or high density modelling foam. If
made from MDF or plywood, the mould might be laser cut or cut with a
fret saw. The mould will include a sprue or runner which will be used to
pour the pewter into.
2) The mould is sandwiched between two pieces of MDF and clamped
together. The top of the mould will be level with the top of the side pieces.
3) The pewter is melted in a ladle and then ladled into the sprue.
4) Once the casting is cooled, it is removed from the mould.
5) The sprue or riser is removed with a junior hacksaw.
6) The casting is then filed, and cleaned up using abrasive wet and dry paper.
7) The casting would then be polished.
OXY-ACETYLENE WELDING PROCESS
1 The metal is prepared by grinding an angle on the edges of the two
pieces to be joined to form a ‘v’ shape. This is done to ensure that the
weld runs through the entire thickness of the metal.
2 The joint area is heated to form a melt pool and at the same time, a steel
filler rod is introduced to the joint area. The melt pool is extended to
form a continuous bead along the length of the joint. The molten metal
will flow to the hottest part of the metal, therefore by moving the torch
along the joint line, a continuous seam is formed.
BRAZING PROCESS
1 The material to be joined is cleaned and degreased.
2 The two pieces are clamped together.
3 A flux is applied (this helps to prevent the joint from oxidising).
4 The joint is heated using an oxy-acetylene or gas/air torch to a
temperature of approximately 850 °C.
5 The brazing rod is applied to the joint area. The brazing ‘spelter’ will
flow along the joint by capillary action to the hottest part, so it can be
made to follow the joint line by manipulating the torch.
SOLDERING PROCESS
1 The metal is cleaned and degreased.
2 The joint area is wired up or clamped.
3 The metal is heated up to the melting point of the solder.
4 The solder is added to the metal. The solder will flow along the joint
using capillary action.
5 The metal is cleaned to remove any flux residue.
