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Metal Processes


Drop Forging Drop Forging Impression-die drop forging is an industrial process used in the production of high quality, strong metal components or products. The main ... – PowerPoint PPT presentation

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Title: Metal Processes

Metal Processes
This PowerPoint presentation takes you through
the various metal work processes that you are
required to be familiar with in order to
successfully complete Unit 3
  • Turning is the production of cylindrical
    components using a centre lathe. The material is
    held firmly in a rotating chuck whilst a cutting
    tool is brought towards it to create the required
    shape. A variety of processes can be carried out
    on the lathe for example turning cylinders,
    creating texture (knurling), accurate drilling
    and threading

Milling Machine
  • Milling machines are powerful pieces of equipment
    which use rotating multi toothed cutters to shape
    the material. There are two types of milling
    machine, horizontal and vertical. The machines
    are named by the position of the cutting tool in
    relation to the workpiece. Milling machines can
    be used as side and face cutters and can also be
    used to cut slots in the material.
  • Milling consists of machining metal by using
    rotating cutters which have a number of cutting
    edges. These tools are known as milling cutters.

Vertical Milling Machine
Horizontal Milling Machine
Milling Cutters
Slot Cutter
Straddle Milling
Milling Cutter
Dovetail Slot
Dovetail Cutter
Angled Face
Angle Cutter
Milling Cutters
Tee Slot Cutter
Flat Surface
Slab Cutter
Die casting
Die Casting
  • Where large quantities of quality castings are
    required in industry, the moulds (dies)need to
    be permanent. These special, alloy moulds are
    costly to produce because they are made in
    sections for easy removal of the components. The
    high operating costs involved make this process
    economically viable for high volume mass
    production where accuracy of shape, size and
    surface finish is essential.
  • Gravity Castings
  • Molten metal is poured into the cavity under
    its own weight. This produces sound, dense
    castings with mechanical properties superior to
    pressure casting (since metal enters the mould
    with less turbulence). This process also traps
    less gas than pressure casting does, leading to
    less porosity.

Die Casting
Hot chamber and cold chamber processes are
used. In both processes molten metal is forced
into a metal die by a hydraulic ram. Thin
section and complex shapes with fine detail are
1. A measure of molten metal is poured into the
charge chamber. 2. An injection piston then
forces the metal into a water-cooled die through
a system of sprues and runners. 3. The metal
solidifies rapidly and the casting is removed,
complete with its sprues and runners.
Die Casting
  • Materials
  • Materials used in this process include low
    melting temperature alloys, lead, zinc, aluminium
    and brass alloys.
  • Identifying Features
  • Section hair lines, ejector pin marks,
    flashes caused by leakage left on internal
    surfaces (these do not interfere with performance
    or appearance), and sprue and runner marks.

Press Forming
Press Forming
  • Press forming involves squeezing sheet metal
    between two matched metal moulds (dies). This
    gives a very strong, shell-like structure. One
    die is the mirror image of the other, apart from
    an allowance for the thickness of the material
    being formed. The machining of these dies is a
    specialised skill. They can be complicated and
    therefore difficult and time consuming to make.
    This makes them very expensive to produce.

The Process The sheet metal component starts out
as a flat sheet or strip 1 A blank is cut
to the required size. 2 The blank is placed in a
press. 3 The product is formed using immense
force. The complete forming process may take
several additional stages of operations to form,
draw (stretch) and pierce the material into its
final shape
Press Forming
  • Materials
  • Sheet metals various steels, aluminium
    alloys, brass, copper
  • Identifying Features
  • Sudden directional changes, i.e. sharp
    edges and deep draws, are avoided to minimise
    overstretching the walls of the product.
    Different operations, e.g flanges, ribs,
    piercing, can be identified.
  • Uses
  • Products used in many everyday activities
    are easily identifiable. These range from pans,
    kettles and stainless steel kitchen sinks to car
    bodies and aircraft panels.

Sand Casting
Sand Casting
Sand casting is the most frequently used metal
casting process. Green, foundry sand is a blend
of silica grains, clay and water. The term
green describes the damp quality which bonds
the sand together. Oil-bound sand gives
excellent results but is relatively expensive and
difficult to reconstitute. There is an element
of waste involved as the sand that is in contact
with the hot metal will burn. This burned sand
needs to be scraped out and disposed of. The
quality of the casting produced depends on the
quality of the pattern. These are normally made
in wood. The pattern requires radiused corners,
drafted sides and a good surface finish. The
sand mould is produced around the pattern, which
is removed to leave a cavity. Molten metal is
poured into the mould and solidifies. When cold,
the mould is broken up to retrieve the casting.
Sand Casting
1. Place the pattern centrally in the drag. 2.
Pack sand around the pattern. 3. Turn the drag
over and attach the cope. 4. Insert sprue pins
and pack sand around them. 5. Remove the sprue
pins. 6. Split the moulding box and cut
gates. 7. Remove the pattern to leave a
cavity. 8. Reassemble the cope so that the mould
is ready to receive the molten metal. 9. Pour the
molten metal into the runner. The melt fills the
mould and exits, along with any gases, via the
Sand Casting
  • Materials
  • Iron, aluminium and non-ferrous alloys are
    most widely used in sand casting. Exceptions
    include refractory (able to withstand high
    temperatures) metals such as titanium. Precious
    metals e.g. gold lend themselves to casting.
  • Identifying Features
  • Complex 3-D components. Mainly solid but
    internal shapes can be produced using cores.
    Thin sections are difficult to mould. Surface
    texture can be poor. Draft angles, fillets,
    rounded corners and strengthening webs will be
    evident and will echo the pattern requirements.
    Other recognisable features include bosses and
    porous surface textures. Fettle marks, due to
    the removal of runners and risers, may be
  • Uses
  • Casting is a versatile process using the
    material properties in the manufacture of engine
    parts, tools and decorative jewellery. Multiple
    mould patterns decrease production time thus
    lowering production costs.

  • Casting in Aluminium
  • The main reason for casting an object is
    that the shape of the object is such that it
    would make matching either very difficult or too
  • There are many ways in which an object can
    be cast, but there are only two ways which are
    suitable for use in the school workshop.
  • 1. Gravity feed casting
  • 2. Investment casting.
  • The main difference being that gravity feed
    casting uses a wooden pattern and so can be used
    for large numbers, where as investment casting
    uses either a wax or a polystyrene pattern and
    therefore only be used once. Both these methods
    come into the category of Green sand moulding,
    which gets its name not from the colour of the
    sand, but because the sand is damp.

Piercing and Blanking
Piercing and Blanking
  • Piercing and blanking are essentially the same
    process, involving the stamping of shapes out of
    sheet metal or metal strip. The differences in
    the process simply depend on which bit of metal
    is to be kept in piercing a shaped hole is made
    in the metal, whereas in blanking a shape is
    stamped out of the metal and then used.

The Process
Piercing The punch and die are shown here in the
closed position. Notice how the punch fits into
the die but does not enter it, stopping instead
as soon as the metal has been cut. Accurate
alignment of the two is essential.
Blanking The main components used for blanking in
mass production are a punch, a die and a stripper
plate. The stripper 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. The punch is attached to a
movable ram.
Progressive Piercing and Blanking
Progressive Piercing and Blanking Many products
requires to be both pierced and blanked. This is
often done in the same press by first piercing
the metal, and then moving it along to another
die and blanking out the desired shape. This
process is called progressive piercing and
blanking. 1 The metal strip is fed into the first
die. 2 A hole is pierced in the metal on the
first stroke of the ram. 3 The ram rises and
metal is moved into position over the blanking
die. 4 Accurate alignment is essential here. 5
The punch descends and the completed component (
in this case a washer) is blanked from the metal
strip. At the same time a hole is pierced in the
next washer. 6 Piercing is normally done before
blanking, as this minimises the risk of
fracturing the metal.
Blanking punch
Piercing punch
Metal Strip
Metal Strip
Finished Washer
Piercing and Blanking
  • Materials
  • Most types of metals can be pierced and
    blanked in sheet or strip form. The metal is
    normally annealed first so as to minimise the
    risk of fracture or tearing.
  • Identifying Features
  • A sheared surface will show two distinct
    areas of deformation and fracture. With the
    correct clearance angles in the punch, this can
    be minimised to give a reasonably smooth edge
    which will require no further finishing.
  • Uses
  • Uses of piercing and blanking include
    component parts for a variety of tool and
    products. Often products made from sheet metal
    that have been press formed are pierced to give a
    decorative finish.

Drop Forging
Drop Forging
  • Impression-die drop forging is an
    industrial process used in the production of high
    quality, strong metal components or products.
    The main advantages are that components can be
    accurately repeated using specially shaped dies
    to control the flow of metal the need for highly
    skilled craftsmen is thus eliminated.

The Process
The die used are very expensive to produce. High
alloy steels are required to prevent heat loss
which causes them to wear too quickly under
impact loads.
1. A hot metal billet is placed between the
dies. 2. The hot metal is forced into the cavity
using a power driven hammer. (Note that the
process may take more than one operation using a
succession of dies.) 3.Excess metal is squeezed
out forming a flashing around the parting line of
the two dies. The amount of flashing is
determined by die wear and the quantity of excess
metal. 4. When the forging is complete the flash
is removed using a trimming die.
Drop Forging
  • Materials
  • Most metals are in alloy form are suited to
    the drop forging process. Alloy steels and
    copper alloys are most common.
  • Identifying Features
  • The function of the product may indicate
    that drop forging is the most appropriate process
    for manufacture, i.e. the product or certain
    parts of the product may require compressive or
    tensile force to be used. Strength to weight
    ratio is a consideration. Visually there may
    well be evidence of flashing and flash removal
    around the edges of the product. Quality
    products may have undergone further finishing to
    eliminate visual evidence of die parting lines.
  • Uses
  • Drop forging metal increases its strength.
    The grain structure of the metal is changed to
    follow the outer contour of the component. This
    provides greater scope for the design of high
    quality metal products. Examples range from hand
    tools such as spanners and plumbing fittings to
    high quality cutlery and domestic appliances.

  • The process of drawing is the main process in
    the production of three dimensional curved
    pressings e.g. drinks cans. The sheet material
    (blank) is held in place by a pressure ring which
    has a highly finished surface plus lubrication to
    minimise friction. A punch is then forced into
    the material drawing it down to form the required
    shape. The depth which can be drawn in one punch
    depends on the type of material, its tensile
    strength and the tool design.

Joining Materials
Joining Materials
  • The manufacture of most products requires
    joining together of materials. Part of the
    designers role is to select the most appropriate
  • Permanent joining methods include adhesives, arc
    welding, fitted joints, riveting, spot welding.
  • Non-permanent methods include nuts, bolts and

  • Mechanical knock down fixings are generally used
    on square cut butt joints on manufactured boards.
    No glue is required but accurately drilled holes
    are essential. Knock-down fixings (fixings) make
    assembly straight forward and have the added
    advantage that dismantling a product is possible.

  • Knock-down fittings are those that can be put
    together easily, normally using only a screw
    driver, a drill, a mallet/hammer and other basic
    tools. They are temporary joints although many
    are used to permanently join together items such
    as cabinets and other pieces of furniture that
    are purchased in a flat pack

  • Soldering, brazing and welding techniques
    are used mainly to join metals. Some
    thermoplastics can also be joined in this way.
  • Arc Welding
  • Heat is obtained by an electric arc via a
    transformer. One lead is attached to the work
    and the other to a grip holder a welding rod. An
    arc is formed when the end of the rod is brought
    near the work. The heat melts the parent metal
    and the filler rod together. The rod is coated
    with flux to prevent oxidation.

Spot Welding
  • The metal is heated and fused together between
    two copper electrodes. Used on thin gauge mild
    steel, e.g. car bodies

  • There are two methods. The traditional method
    uses soft iron, aluminium or copper for snap,
    countersunk and flat head rivets in conjunction
    with a hammer and rivet set.

  • Where the use of a hammer is to be avoided,
    controlled pressure is applied to a pop rivet
    using a pop-riveting gun. Also used for
    blind riveting.

The rivet pliers are pushed on to the pin of the
rivet and the handles are pulled together. As
this happens the pin head is pulled into the
rivet and the end of the rivet is expanded.
Eventually the pin will break off leaving the
rivet permanently fixed in position holding the
two pieces of plastic / aluminium together.
The pop rivet is passed through both holes in the
sheet plastic / aluminium.
The two pieces of plastic or aluminium are
drilled to a size slightly larger than the rivet
  • The screw thread has the advantage of
    enabling items to be taken apart for inspection
    or maintenance purposes. Nuts, bolts and set
    screws can be obtained in various forms. There
    are numerous designs of spanners for use with
    square- and hexagonal-headed nuts and bolts, just
    as there are keys for socket screws.

  • Screws are used to fasten together boards, panels
    and fittings such as hinges and brackets. Pieces
    can be taken apart and reassembled without
    damage. Screwdrivers are available in a variety
    of blade types, e.g. slot and pozidrive. Effort
    in driving screws home can be minimised by using
    electrically powered screw guns

Other Things To Consider
  • Permanent, semi-permanent or temporary?
  • Types(s) of material(s)
  • allow for movement
  • surface area
  • indoor or outdoor?
  • Are cramps to be used?
  • Time (setting time)

Finishing Metal
  • Finishing bright steel
  • Stage 1 - After shaping with coarse file and
    smooth file, complete filing by draw-filing.
    Always work in the same direction along the metal
    and make sure that each stage removes all marks
    left by the previous one.
  • Stage 2 - Finish by using different grades of
    emery cloth, first coarse, then fine, and finally
    after all marks have been removed add a little
    oil to the fine cloth for final finishing
  • Stage 3 - To protect the metal from rust, smear
    it with light grease.
  • Oil finishing black steel
  • Stage 1 - Remove all loose scale from forging,
    grease, etc.
  • Stage 2 - Either dip the metal in machine oil and
    burn it into the metal, or heat the metal to dull
    red heat and quench it in oil.
  • Stage 3 - Wipe off surplus oil and polish with
    black boot polish.

  • Painting metal
  • Stage 1 - Thoroughly clean and degrease the
    metal. Paraffin or special degreasers will clean
    badly affected parts while hot water with soda or
    detergents will remove light oil and dirt.
  • Stage 2 - Find a dust free place to work, and
    make arrangements for supporting the work while
    painting and drying before starting.
  • Stage 3 - For maximum protection apply primer,
    undercoat and topcoat. For inside work one or
    two coats of topcoat alone are adequate. Two
    thin coats are always better than one thick one.
  • Lacquering
  • Stage 1 - Thoroughly clean, polish and degrease
    the metal.
  • Stage 2 - Apply the lacquer or varnish with a
    best quality soft brush to preserve the finish.