1. Bulk Deformation Processes in Metalworking

2. Rolling
Rolling - deformation process with thickness reduced by compressive forces exerted by two opposing rolls.

3. Rolling Analysis Conservation of material
Continuity of volume flow rate
Forward slip
Rolling force, F

4. Rolling Analysis Where the deformation strain
and the average flow stress
The torque required for the deformation process
The power required by the process is

5. Rolling Mechanics
The rolling process is governed by the frictional force between the rollers and the workpiece. The frictional force at the entrance side is higher than that at the exit side. This allows the roller to pull the workpiece towards the exit end.

6. Friction vo<vr<vf
Maximum draft, which is the thickness reduction, is given as 2R.
Coefficient of friction depends on lubrication, typically:
cold working 0.1
warm working 0.2
hot working 0.4

7. Material and Process Parameters
Material Parameters
ductility
coefficient of friction
strength, modulus and Poisson’s ratio
Process Parameters
roller speed
power
draft
lubrication

8. Shape Rolling
In addition to the material and process parameters, the rollers will acts as a set of dies and have to be pre-formed to take the negative shape of the cross-section.
There may be more than one set of rollers required to reduce the workpiece to the appropriate shape.

9. Rolling Mill Configurations
a) two high b) three high c) four high
d) cluster mill e) tandem rolling mill

10. Ring Rolling To make a larger and thinner ring from the original ring
Usually a hot rolling process for large rings and cold rolling for small rings
Typical applications: bearing races, steel tires, rings for pressure vessel.

11. Thread Rolling Production of external thread Cold rolling
High and competitive production rate (up to 8 parts per second)

12. Gear Rolling Similar to the screw thread. Typically for helical gears
Shares the same advantages:
better material usage
smoother surface
stronger thread due to work hardening
better fatigue resistance due to compression

13. Roll Piercing Hot working process
Production of Seamless thick-wall tubes

14. Forging
Open-die forging
Flashless forging
Impression-die forging

15. Mechanics of Forging Under ideal condition: Where F = forging force
Yf = flow stress
A = cross-section of part

16. Forging In open-die forging, barreling occurs.
But with hot forging, the issue is complicated by the thermal distribution within the workpiece and the associated flow of metal.

17. Shape factor The actual forging force is greater than the ideal case.
The shape factor is to cover the effect of barreling and the friction effect.
Open-die forging is not a net-shape process and will require subsequent machining to dimension.
Load-stroke curve

18. Open-die Forging
Fullering
Edging
Cogging

19. Open-die Forging Fullering Edging Cogging
Reducing workpiece cross section to prepare for subsequent shaping action. Dies with convex surface cavity are used.
Edging
Similar to Fullering, but the dies have concave surface cavitiy.
Cogging
Open dies with flat or slightly contoured surfaces to reduce cross-section and to increase length.

20. Impression-die Forging
Dies containing the inverse of the shape of the part. Flash is allowed on the parting surface. The flash serves as a constraint for metal flow in the die and help to fill the intricate details of the cavity.
Higher forging forces are required in this process than open-die forging. The shape factor generally will have a higher value.

21. Impression-die Forging
The forces are largest at the end of the process when the projected area of the blank and the friction is largest.
Again, progressive dies are needed to transform the starting blank into a final desired geometry.
Machining is needed to produce the fine tolerance needed.

22. Impression-die Forging
Pros:
high production rate
conservation of metal
greater strength
favorable grain orientation
Forging Machining

23. Shape Factor

24. Flashless Forging
Conventional forging part Precision forging part

25. Flashless Forging
The volume control is important and the outcome is precision re-production of inverse of cavity geometry. Typically for aluminum and magnesium alloy.

26. Corning

27. Drop Hammer and Dies
Webs - Thin section parallel to parting line.
Ribs - thin section perpendicular to parting line
Gutter - area for containing flash
Dies are normally made from tool steel with high impact strength and high wear resistance.

28. Upsetting and Heading Upsetting and Heading
The leading section of the stock is forged to form a head section using closed-die forging.

29. Upsetting and Heading
Upsetting is used to form heads of screw and bolt with different geometric forms.

30. Swaging
Swaging used to reduce the cross-sections of forged rods or tubes using a set of rotating dies. A mandrel is sometimes used to control the internal form of the tube.
Radial forging rotates the stock rather than the die.

31. Roll Forging

32. Orbital Forging
Small contact area reduce the forging force required substantially.

33. Hobbing
To press the die against the softer blank to form the final shape.

34. Trimming
Trimming is a shearing process to remove the flash from the workpiece.

35. Design Considerations
Material
Die design
Machine
Machine processing range
Machine process setting

36. Design Considerations
Material
Ductility
Strength
Plastic deformation law (constitutive relationship)
Coefficient (Die/workpiece)
Variation of properties at processing temperature range

37. Design Considerations
Die Design
Number of die stations (progressive die)
Geometric complexity of the part
Die geometric details
Draft angle, fillet, radii
Webs and ribs
Flash
Parting surface and parting direction
Die material
Die life

38. Design Considerations
Machine processing range
Maximum forging force
Maximum power
Maximum speed
Maximum die size

39. Design Considerations
Machine process setting
No. of stations
Velocity profile
Temperature / time profile
Force