0. Introduction to Manufacturing
Chapter 14: Forging

1. Forging
Metal-forming process in which the workpiece is shaped by compressive forces applied through various dies and tools.
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2. Forging Cold Forging Hot 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.
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3. Forging Forgeability Forging is a discrete (individual) parts process
Capability of a material to undergo deformation without cracking.
Forging is a discrete (individual) parts process
Forging is a near net shape process
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4. 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.
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5. 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
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6. 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).
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7. Impression-Die Forging (Cont.)
blank (part which has been cropped or cut from bar stock).
blocking (rough shaping with dies).
finishing (using impression dies, forging the final part shape).
trimming (removing the flash).
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8. 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.
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9. 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 )
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 )
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10. 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)
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11. 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.
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12. 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
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13. Related Forging Operations
Rotary Swaging
Radial Forging (circular shaped parts)
Use reciprocating dies controlled by a cam
Tube swaging
Mandrel and dies
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14. Forging Machines Presses Hammers hydraulic mechanical screw
gravity drop
power drop
Counterblow (two hammers)
high-energy-rate Machines (pneumatic)
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