1. Metal forming processes
in manufacturing

2. Classification of manufacturing processes
A complex geometry
(shape, size, accuracy,
tolerances, appearance,
Properties)
A given material
(shapeless or a simple geometry)
Primary shaping processes
Casting, melt extrusion, die casting, etc.
Rolling, extrusion, forging, bending, drawing
(plastic deformation)
Metal forming processes
Sawing, turning, milling
(by removing metal)
Metal cutting processes
Heat treatment, surface hardening
(unchanged in shape, changed in properties)
Metal treatment processes
Metallurgical joining : welding,
Mechanical joining : riveting, shrink fitting, assembly
Joining processes

3. Metal forming processes in manufacturing
Massive forming processes (Bulk forming processes)
: forging, extrusion, rolling, drawing
Material type
Large plastic deformation, appreciable change in shape or cross section,
The portion of permanent deformation >> elastic deformation
Elastic deformation is negligible
Sheet forming processes
: deep drawing, stretch forming, press forming
Sheet, changes in shape, not in section, permanent=elastic, e/recovery
Cold forming processes : room temperature
Forming temp.
Hot forming processes : above the recrystallization temp.
☞ Most materials behave differently under different temperature condition
; [cold forming] Y.S. increases with an increase of strain
; [hot forming ] Y.S. increases with an increase of strain rate
Attractive points
☞ in case where the part geometry is of moderate complexity
☞ in case where the production volume are large
☞ in case where tooling costs per unit product should be kept low

4. Variables and Classification of Metal Forming Processes

5. Significant variables in a deformation process
Flow stress as a function of strain, strain rate, temperature,
microstructure (constitutive equation)
Billet material
Workability as a function of strain, strain rate, etc
(forming limit diagram)
Surface condition
Mechanical properties (thermal/physical)
Geometry of tools
Tooling
Surface condition
Heat treatment / hardness
Accuracy / tolerances
Lubricant type and condition
Interfacial
condition
Cooling characteristics of the interface layer
Friction

6. Significant variables in a deformation process
Deformation mechanics / model used for analysis
Deformation
zone
Metal flow and velocity
Stresses (variation during deformation)
Temperatures (heat generation and transfer)
Speed / Production rate
Equipment
Force / Energy capabilities
Rigidity and accuracy
Dimensional accuracy
Product &
Environment
Surface finish
Plant and production facilities and control

7. Description of Metal Forming
Processes

8. Closed die forging Closed die forging with flash
☞ a billet is formed (usually hot) in dies (usually with two halves)
☞ the excess of the material is extruded through a restrictive narrow gap

9. Closed die forging Closed die forging without flash
☞ in this process, a billet with carefully controlled is deformed by a punch
☞ in order to fill a die cavity without any loss of material, the punch and
the die may be made of one or several pieces

10. Closed die forging Coining process
☞ coining is a closed die forging (usually called restriking)
☞ all surfaces of the work are confined or restricted
☞ resulting in well-defined imprint of the die on the workpiece

11. Forward extrusion
☞ A punch compresses a billet (hot or cold) confined in a container
☞ the billet material flows through a die in the same direction as the punch

12. Backward extrusion
☞ a moving punch applies a steady pressure to a slug confined in a closed die
☞ it forces the metal to flow around the punch in a direction
opposite the punch direction

13. Open die forging ☞ Open die forging is a hot forming process
☞ the metal is shaped by hammering or pressing between flat or simple
contoured dies.
☞ most of shafts can be manufactured by this process

14. Orbital forging
☞ orbital forging shapes parts by incrementally forging a slug between
an rotating upper die and a non-rotating lower die
☞ the lower die is raised axially toward the upper die, which is fixed axially

15. Upsetting
☞ Through the upsetting process, the cross sectional area in increased

16. Sheet rolling
☞ a hot or cold forming process for reducing the cross-sectional area
☞ this process uses rotating rolls
☞ the rolled material (plate) elongates and spreads at the same time

17. Shape rolling
☞ Shape rolling is a cold or hot forming process for reducing as well as
shaping the cross section of the metal
☞ the metal passes through a series of rotating sets of rolls with grooves

18. Tube rolling
☞ the process of reducing the cross section and the diameter of a tube

19. Ring rolling
☞ a process where a hollow circular blank is formed into a ring
☞ a main roll presses on the outside diameter of the blank
☞ shaped cross section is obtained by contouring of the mandrel and the roll

20. Shear forming / spinning
☞ a process for hot or cold seamless shaping of dished part
☞ it uses the combined forces of rotating and pressure

21. Drawing
☞ drawing is the process of reducing the cross-sectional area and the shape
of a rod, bar, tube or wire by pulling through a die

22. Deep drawing
☞ a sheet blank is forced by a punch into a die to form a deep recessed part
☞ this process is used to produce cylindrical cup shape

23. Bulging / hydroforming
☞ an internal pressure is applied so as to form a tube to the desired shape
☞ the internal pressure can be delivered by expanding a punch through
a fluid

24. Roll bending
☞ roll bending gives a curvature to a sheet, bar or shaped section by bending it
between two or three cylindrical rolls

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