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Introduction to Manufacturing

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Introduction to Manufacturing Chapter 14: Forging Forging Metal-forming process in which the workpiece is shaped by compressive forces applied through various dies ... – PowerPoint PPT presentation

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Title: Introduction to Manufacturing


1
Introduction to Manufacturing
  • Chapter 14 Forging

2
Forging
  • Metal-forming process in which the workpiece is
    shaped by compressive forces applied through
    various dies and tools.

3
Example Blacksmith Hammer and anvil
4
Forging
  • Forgeability
  • Capability of a material to undergo deformation
    without cracking.
  • Forging is a discrete (individual) parts process
  • Forging is a near net shape process

5
Metal flow and grain structure controlled parts
have good strength
  • Landing gear
  • Jet engine shafts
  • Bolts
  • Connecting rods
  • Hand tools

6
Forging classified cold or hot
7
Cold Forging
  • Requires greater forces and workpiece materials
    must have sufficient ductility at room
    temperature good surface finish and dimensional
    accuracy.

8
Hot Forging
  • Requires smaller forces, not as good finish or
    dimensional accuracy usually require additional
    machining.

9
Open-Die Forging
  • Upsetting or flat-die forging
  • Simplest forging process.
  • Solid workpiece is set between two flat dies and
    reduced (height) through compression.

10
Barreling
  • outward bowing of material
  • Two causes
  • 1.) by friction at die-work piece interface
  • minimized by use of lubricants.

11
Barreling
  • (2) by hot work piece between cold dies
  • Material cools at die interface and resists
    deformation

12
Cogging
  • Drawing out
  • Operation where the thickness of a bar is reduced
    by successive forging steps at certain intervals.
  • Typical for parts such as I-beams which must be
    pre-shaped before rolling

13
Fullering
  • Distribute material away from die

14
Edging
  • Gather material into die

15
Impression-Die Forging
  • Work piece takes shape of die cavities
    (impressions).
  • Flash material which flows out from dies
    (frictional resistance from cooling flash causes
    material to fill the inside of the die cavity).

16
Closed-Die Forging
  • Also called precision forging
  • flashless forging (flash does not form).
  • workpiece completely fills the die cavity. Volume
    of material is precise.
  • Economical - eliminates trimming flash

17
Closed die forging (cont.)
  • Greater forces to obtain fine detail
  • Al and magnesium good because malleable
  • Less material wasted
  • Gears, connecting rods, etc.

18
Coining
  • Another closed die process
  • Produces fine details
  • No lubricants used can be trapped in die
    cavities dont compress
  • pressures five to six times the strength of
    material.

19
Related Forging Operations
20
(1) Heading
  • upsetting operation, usually performed at the end
    of a round rod or wire to produce a large cross
    section
  • heads of bolts, screws nails, rivets, etc.

21
(2) Piercing
  • indenting, without breaking, the surface of a
    workpiece with a punch to produce a cavity or an
    impression

22
(4) Roll Forging
  • the cross section of a bar is reduced or shaped
    by passing it through a pair of rolls with shaped
    grooves
  • leaf springs, hand tools, discrete parts

23
(5) Skew Rolling
  • similar to roll forging
  • Ball bearing production

24
(6) Orbital Forging
  • upper die moves along an orbital path above the
    part which is also spinning.

25
(7) Incremental Forging
  • process where a blank is forged into a shape in
    several small steps (the die penetrates the blank
    at different depths across the surface). Similar
    to cogging.

26
(8) Isothermal Forging
  • Hot die forging
  • Dies heated to same temp as workpiece
  • Good for complex parts with dimensional accuracy

27
Forging die design
  • Most important rule in die design
  • Work piece material must flow in direction of
    least resistance
  • Machining allowance used

28
Die inserts
  • Separate sections
  • Reduce cost of making dies

29
Die lubricants
  • Slow rate of cooling
  • Improve metal flow
  • Serve as parting agent
  • Not for coining precision forging

30
Forging Machines
31
Presses
  • Hydraulic
  • Mechanical
  • Screw

32
Hammers
  • Gravity drop free falling ram
  • Power drop stroke accelerated by steam, air, or
    hydraulic

33
Hammers (cont.)
  • Counterblow (two hammers simultaneously approach
    each other
  • High-energy-rate machines - ram accelerated by
    high pressure part forged in one blow
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