Product design

• Press forming


  Used to shape sheet metal into 3D forms, for example metal seats, car body panels, boxes and containers
• Press forming


  Only usually used in mass production or large-scale batch production due to the cost and complexity of making the dies
• Press forming dies


  • Made from hardened steel
  • Often machined using spark erosion techniques (where a material is worn away using sparks)
  • Hand burnished to give a high-quality surface
  • Making dies is a highly skilled, specialist job, and is therefore costly
• Only when manufacturers can recoup the costs by producing and selling many thousands of the same item would such expenditure on press forming dies be justified
• Press forming components


  • Drawing force
  • Holding force
  • Blank
  • Punch
  • Male die or punch
  • Blank holder
• The product life cycle is the stages that products go through from introduction to decline
• Press forming process


  1. Sheet metal is clamped over a die

  2. A hydraulic press pushes the die into the sheet metal

  3. Cutting blades may punch holes and trim excess

  4. The hydraulic die is lowered and the pressed sheet component is removed

  5. The sheet may be placed into further press forming machines for additional pressing
• Spinning


  An alternative process to press forming for shaping objects such as the body of stainless steel kettles, saucepans or other products with radial symmetry
• Spinning process


  1. Sheet of metal is spun at high speed as it is pushed over a former or mandrel

  2. Spun products can be identified by parallel lines that are formed on the surface of the metal during the process
• Spinning


  • Typically used in mass production
  • Can be set up using computer controlled machines so that thousands of identical products can be made
  • Can be used in batch production, particularly where dome-shaped items need to be made but the quantity required does not justify the costs associated with press forming
• Spinning process steps


  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, this starts to stretch the metal over the mandrel

  3. The roller tool is moved along the mandrel as pressure is maintained against the rotating blank
• Spinning


  • Shaping the body of stainless steel kettles
  • Shaping the body of saucepans
  • Shaping other products with radial symmetry
• Cupping and deep drawing process

  • Used to form tube-like shapes such as fire extinguishers and high pressure aerosol cans
  • Considered 'deep drawing' when the depth of the pressing exceeds the diameter
• Cupping and deep drawing process


  1. Clamping pressing blank over deep drawing die using pressure pad or clamping ring

  2. Hydraulic press moves deep drawing punch to be in contact with blank and pushes blank into die cavity to make cup shape

  3. Cup is then pressed further down through deep drawing die to make desired tube shape
• Cupping and deep drawing

  • High setup costs of hydraulic presses and dies
  • Only suitable for mass or continuous production of identical items
• Drop forging


  Used to shape hot metal into finished products
• Drop forging


  • Finished product needs to be tough (impact resistant) and hard
  • Typically used for products such as spanners, pliers and screwdriver shafts
  • Allows hot metals to be formed and maintains the internal grain structure and thus the strength required
• Mass production of identical items using drop forging


  • Dies are dedicated to making one specific item
  • Dies can be changed quickly to make other items using the same hydraulic ram
• Drop forging process


  1. Die made from cast tool steel is secured to the top of an anvil

  2. Ram equipped with a die that resembles a mould

  3. Metal billet to be forged is heated to above its recrystallisation temperature

  4. Heated billet is placed by an operator into the anvil die

  5. Hydraulic ram is brought down with force to make the hot billet spread around the shape of the die

  6. Ram is lifted and the completed product removed for cooling and finishing
• Bending


  Bending sheet or plate metal in industry is done using a machine called a press brake
• Bending process


  1. Clamping the stock metal between a matching punch and die

  2. Hydraulic, pneumatic or mechanical brake holds the metal sheet or plate

  3. Lowers the punch to bend the material to shape
• Common dies used in press brakes

  • V shaped
  • 90 degree
  • Radius
• Unlike press forming, bending does not usually combine any punching or trimming
• Bending as a production method

  • Can be done as a one-off
  • More typically used in large-scale batch production in industry
• Rolling


  A metal forming process in which the stock metal material is passed through sets of rollers to reduce the thickness of the material
• Rolling


  1. Passed through sets of rollers

  2. Reduce thickness of material
• Other products made by rolling

  • Rails for railway tracks
• Hot rolled metal


  • Has mechanical properties that are uniform throughout the sample
  • No deformation or stresses which could result in a fault
• Cold rolled metal


  • Has a tighter tolerance because carbon deposits are not formed during the rolling process
  • Surface finish is much better
• MIG welding


  A fabrication process used for thin gauge metal (usually medium carbon steel) or aluminium, particularly tube and box section
• MIG welding


  1. Uses an electric arc to create heat which melts the joint area

  2. A wire electrode (made from the same metal as the material being joined) also melts in the arc and fills the gap between the two pieces being joined

  3. The operator swirls the welding gun as they move it over the joint, to form a continuous bead of weld

  4. The electrode wire is stored on a reel and advances through the welding 'gun' as the trigger is pressed
• Shielding gas


  MIG welding uses an inert gas such as CO2 or argon to form a 'flux' shield over the area that is being joined, replacing the oxygen at the joint area to prevent oxidisation and help the weld form properly
• MIG welding is a process that is suitable for one-off fabrication, but it can be used as a process stage in the mass production of a product
• Components of MIG welding

  • Wire-fed
  • Consumable electrode
  • Arc
  • Shielding gas
• TIG (tungsten inert gas) welding


  A process used to weld metals such as stainless steel, non-ferrous metals like aluminium, copper or magnesium alloys
• TIG welding


  1. Electric arc welding process

  2. Electrode made from tungsten does not melt

  3. Separate filler rod is used

  4. Gas shield of argon or helium is used to protect the weld area from oxidisation
• TIG welding


  • Allows for greater control by the operator
  • Creates more accurate, stronger welds
  • Requires higher levels of skill
  • Quite a slow method
• Where TIG welding might be used

  • Fabricating stainless steel ladders for boats or swimming pools
  • Welding stainless steel car exhausts
• Oxy-acetylene welding


  Used to weld low carbon steel sheet, tube or plate where arc welding processes are not available
• Oxy-acetylene welding


  • Processes such as MIG welding, or electric arc welding, have made the use of oxy-acetylene almost obsolete
  • Useful for quick repair jobs or in remote locations where there is no electric power supply