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.
Engr 241-R1

3. Example – Blacksmith Hammer and anvil
Engr 241-R1

4. 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
Engr 241-R1

5. Metal flow and grain structure controlled – parts have good strength
Landing gear
Jet engine shafts
Bolts
Connecting rods
Hand tools
Engr 241-R1

6. Forging classified cold or hot
Engr 241-R1

7. Cold Forging
Requires greater forces and workpiece materials must have sufficient ductility at room temperature; good surface finish and dimensional accuracy.
Engr 241-R1

8. Hot Forging
Requires smaller forces, not as good finish or dimensional accuracy; usually require additional machining.
Engr 241-R1

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.
Engr 241-R1

10. Barreling outward bowing of material Two causes
1.) by friction at die-work piece interface
minimized by use of lubricants.
Engr 241-R1

11. Barreling (2) by hot work piece between cold dies
Material cools at die interface and resists deformation
Engr 241-R1

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
Engr 241-R1

13. Fullering
Distribute material away from die
Engr 241-R1

14. Edging
Gather material into die
Engr 241-R1

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).
Engr 241-R1

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
Engr 241-R1

17. Closed die forging (cont.)
Greater forces to obtain fine detail
Al and magnesium good because malleable
Less material wasted
Gears, connecting rods, etc.
Engr 241-R1

18. Coining: Another closed die process Produces fine details
No lubricants used – can be trapped in die cavities – don’t compress
pressures five to six times the strength of material.
Engr 241-R1

19. Related Forging Operations
Engr 241-R1

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.
Engr 241-R1

21. (2) Piercing
indenting, without breaking, the surface of a workpiece with a punch to produce a cavity or an impression
Engr 241-R1

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
Engr 241-R1

23. (5) Skew Rolling similar to roll forging Ball bearing production
Engr 241-R1

24. (6) Orbital Forging
upper die moves along an orbital path above the part which is also spinning.
Engr 241-R1

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.
Engr 241-R1

26. (8) Isothermal Forging Hot die forging
Dies heated to same temp as workpiece
Good for complex parts with dimensional accuracy
Engr 241-R1

27. Forging die design Most important rule in die design
Work piece material must flow in direction of least resistance
Machining allowance used
Engr 241-R1

28. Die inserts
Separate sections
Reduce cost of making dies
Engr 241-R1

29. Die lubricants Slow rate of cooling Improve metal flow
Serve as parting agent
Not for coining – precision forging
Engr 241-R1

30. Forging Machines
Engr 241-R1

31. Presses
Hydraulic
Mechanical
Screw
Engr 241-R1

32. Hammers Gravity drop – free falling ram
Power drop – stroke accelerated by steam, air, or hydraulic
Engr 241-R1

33. Hammers (cont.)
Counterblow (two hammers simultaneously approach each other
High-energy-rate machines - ram accelerated by high pressure – part forged in one blow
Engr 241-R1