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
Forging

• Cold Forging
• Requires greater forces and workpiece materials
  must have sufficient ductility at room
  temperature good surface finish and dimensional
  accuracy.
• Hot Forging
• Requires smaller forces, not as good finish or
  dimensional accuracy usually require additional
  machining.

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
Open-Die Forging

• (upsetting or flat-die forging)
• Simplest forging process.
• Solid workpiece is set between two flat dies and
  reduced (height) through compression.
• Barreling (outward bowing of material) minimized
  with the use of lubricants.

6
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

7
Impression-Die Forging

• Work piece forms in between shape of die cavities
  (impressions).
• Flash material which flows out from dies
  (frictional resistance causes material to fill
  the inside of the die cavity).

8
Impression-Die Forging (Cont.)

1. blank (part which has been cropped or cut from
   bar stock).
2. blocking (rough shaping with dies).
3. finishing (using impression dies, forging the
   final part shape).
4. trimming (removing the flash).

9
Closed-Die Forging

• flashless forging (flash does not form).
• workpiece completely fills the die cavity. Volume
  of material is precise.
• Precision Forging near-net-shape, net-shape
  forging (volume control gears, connecting
  rods)
• Coining pressures five to six times the strength
  of material.

10
Related Forging Operations

• Heading
• upsetting operation, usually performed at the end
  of a round rod or wire to produce a large cross
  section (bolts, rivets) warm, cold, or hot
  process. (Fig. 14.11)
• Piercing
• indenting, without breaking, the surface of a
  workpiece with a punch to produce a cavity or an
  impression (pressure is usually 3-5 times the
  strength of material). (Fig. 14.12)

11
Related Forging Operations

• Hubbing
• pressing a hardened punch into the surface of a
  block of metal to produce a cavity (create dies
  for tools, tableware, etc.).
•  
• 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)

12
Related Forging Operations

• Skew Rolling
• similar to roll forging
• Ball bearing production
• Orbital Forging
• upper die moves along an orbital path above the
  part which is also spinning.

13
Related Forging Operations

• 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.
•  
• Isothermal Forging
• Hot die forging

14
Related Forging Operations

• Rotary Swaging
• Radial Forging (circular shaped parts)
• Use reciprocating dies controlled by a cam
• Tube swaging
• Mandrel and dies

15
Forging Machines

• Presses
• hydraulic
• mechanical
• screw
• Hammers
• gravity drop
• power drop
• Counterblow (two hammers)
• high-energy-rate Machines (pneumatic)