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Manufacturing Processes > Section 4: Bulk Deformation > Flashcards

Section 4: Bulk Deformation Flashcards

1
Q

Bulk Deformation

A

Metal forming operations which cause significant shape change by deforming metal parts whose initial form is bulk rather than sheet.
Causes plastic flow into the desired shape

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2
Q

plastic flow

A

permanent deformation when a material hits a critical stress value

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3
Q

What temperature processes is bulk deformation performed under

A

cold, warm, and hot working

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4
Q

Advantage of hot working bulk deformation

A

Significant Shape change

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5
Q

Advantage of cold working bulk deformation

A

Strength is increased

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6
Q

Primary benefit of bulk deformation

A

Little to no waste
little or no machining required

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7
Q

Four Basic Bulk Deformation Processes

A
  • Rolling
  • Forging
  • Extrusion
  • Wire and bar drawing
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8
Q

Rolling w/ goals

A
  • Slab or plate is squeezed between opposing ROLLS
  • the rolls act as compressive forces that reduce the crosssection (reduce thickness)
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9
Q

Forging

A

Work is squeezed and shaped between opposing DIES

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10
Q

Extrusion

A

work is squeezed through a die OPENING, thereby taking SHAPE of the OPENING

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11
Q

Wire and bar drawing

A

Diameter of wire or bar is REDUCED by PULLING it through a die opening

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12
Q

Difference between Extrusion and Wire & bar drawing

A

In extrusion the work is SQUEEZED through an opening to take the shape of that opening

In Wire & bar drawing the work is PULLED through an opening with the goal of reducing the diameter

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13
Q

4 Types of Rolling and their 2 respective bases and functions

A

Based on workpiece geometry:
- Flat Rolling: used to reduce the thickness of a rectangular cross-section
- Shape Rolling: Square cross section is formed into a shape such an I-beam

Based on Work temperature:
- Hot Rolling: can achieve significant deformation
- Cold Rolling: produces sheet and plate stock

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14
Q

4 types of Rolling and their bases

A

Workplace Geometry:
- Flat Rolling
- Shape Rolling
Work Temperature:
- Hot Rolling
- Cold Rolling

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15
Q

What is Thread Rolling

A

Bulk deformation process used to form threads on cylindrical parts by moving them between two dies

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16
Q

Benefits of Thread Rolling

A
  • Important for mass production of bolts and screws
  • Performed as Cold Working
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17
Q

Advantages of thread rolling over thread cutting

A
  • higher production rates
  • better material utilization
  • stronger threads and better fatigue resistance
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18
Q

Ring Rolling

A

Deformation Process in which a thick-walled ring of smaller diameter is rolled to form a thin-walled ring of larger diameter

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19
Q

Roll Piercing

A

Formation of internal stresses and cavity by compression of cylindrical part
Can be used for seamless tubing

20
Q

What is Forging

A

Deformation process in which work is compressed between two dies

21
Q

What is the oldest metal forming operation

A

Forging

22
Q

Common products of forging

A

engine crankshafts, connecting rods, gears, jet engine turbine parts

23
Q

What is Impact forging

A

Forge hammer - applies impact

24
Q

What is Press forging

A

Forge Press - applies gradual force

25
Q

What is Open-die forging

A

work is compressed between two flat dies, allowing metal to flow laterally with minimum constraint to produce a desired cross-sectional shape

26
Q

What is Impression-die forging

A

Compression of work piece by two dies
- flash is created

27
Q

What is Flashless forging

A

compression of a work piece in punch and die tooling
- no excess flash

28
Q

Importance of flash in impression-die forging

A
  • As flash forms, friction resists continued metal flow into the gap, constraining the metal to fill the die cavity
  • In hot forging, metal flow is further restricted by cooling against die plates
29
Q

Advantages & Limitations of Impression-die forging

A

Advantages:
-higher production rates
- less waste of metal
- greater strength
- Favorable grain orientation of metal
Limitations:
- Not capable of close tolerances
- Machining is often required to achieve accuracies and features needed

30
Q

Notes on flashless forging

A
  • starting work volume must equal die cavity volume within very close tolerance
  • process control more demanding than impression-die forging
  • best suited to part geometries that are simple and symmetrical
  • often classified as a precision forging process
31
Q

Types of forging hammers and functions

A

gravity drop hammers - impact energy from the falling weight of a heavy ram
power drop hammers - accelerate the ram with pressurized air or steam

32
Q

disadvantage of forging hammers

A

impact energy is transmitted through anvil into the floor of the building

33
Q

What are forge hammers commonly used in

A

impression-die forging

34
Q

In general, extrusion is used to produce what?

A

long parts of uniform cross-sections

35
Q

two basic types of extrusion

A

-direct (or forward)
- indirect (or backward/reverse)

36
Q

Direct Extrusion

A
  • starting billet cross section is usually round
  • Extrudate is determined by opening
  • as the ram approaches the opening, the remaining portion that cannot be forced through is called the butt
  • also called forward extrusion
37
Q

Indirect Extrusion

A
  • aka backward or reverse extrusion
  • lower rigidity of hollow ram
  • difficulty in supporting extruded product as it exits die
  • can produce a solid cross-section using a hollow ram only
  • can produce a hollow cross-section using a solid ram only
38
Q

Advantages and Limitations of Extrusion

A

Advantages:
- Variety of shapes possible, especially in hot extrusion
- Grain structure and strength enhanced in cold and warm extrusion
- close tolerances possible, especially in cold extrusion
- potentially little to no waste
Limitations:
- part cross-section must be uniform throughout length

39
Q

what is Hot extrusion and its goal

A
  • prior heating of billet to above its recrystallization temperature
  • reduces strength and increases ductility of metal, permitting more size reductions and more complex shapes
40
Q

what is the goal of Cold extrusion

A
  • generally used to produce discrete parts
41
Q

Impact extrusion

A

high speed cold extrusion

42
Q

Difference between wire drawing and bar drawing

A

stock size, equipment, and terminology
- Bar drawing: large diameter bar and rod stock
- Wire drawing: Small diameter stock

43
Q

Typical Drawing practice

A

-cold working
- use round cross sections

44
Q

Products of wire and bar drawing

A
  • Wire: fencing, hangers
  • Rod stock for nails, screws, springs
  • Bar stock: metal bars for machining, forging, etc
45
Q

Bar Drawing

A

-Accomplished as a single draft (the stock is pulled through one die opening)
-Beginning stock has a large diameter and is a straight cylinder
- requires a batch type operation

46
Q

Wire Drawing

A

Continuous drawing machines consisting of multiple draw dies (4-12) separated by accumulating drums:
- Each drum (capstan) provides force to draw wire stock through the upstream die
- Each die provides a small reduction, so the desired total reduction is achieved by the series of dies
- Annealing sometimes required between dies to relieve work hardening

Manufacturing Processes (7 decks)

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