Transcript New approaches in Materials and Manufacturing Education

Unit 5. Selecting
processes:
shaping, joining and
surface treatment
New approaches to Materials Education - a course authored by
Mike Ashby and David Cebon, Cambridge, UK, 2007
© MFA and DC 2007
Outline
•
Processes and their attributes
• Screening by attributes
• Selecting shape-forming processes
• Selecting joining processes
• Selecting surface-treatment processes
• Exercises
More info:
• “Materials: engineering, science, processing and design”, Chapter 18 and 19
• “Materials Selection in Mechanical Design”, Chapters 7 and 8
© MFA and DC 2007
Manufacturing processes
Mould
Primary
shaping
Casting
Molding
PM methods
Granular Polymer
Nozzle
Secondary
shaping
Cylinder
Heater
Machining
Drilling
Cutting
Screw
Injection moulding
No.8-CMYK-5/01
Machining
Surface
Treating
Joining
Welding
Adhesives
Fasteners
Painting
Polishing
Heat treating
Welding
Painting
© MFA and DC 2007
Data organisation: the PROCESS TREE
Kingdom
Family
Casting
Joining
Process
data-table
Shaping
Surfacing
Attributes
Compression
RTM
Blow molding
Material
Injection molding
Material
Deformation
Rotation
Molding
Injection
Composite
RTM
Powder
Blow
Rapid prototyping
Each family has
attributes that differ.
Difficult !
Member
Class
Shape
Material
Shape
Size
Range
Shape
Size
Range
Min.
section
Size
Range
Min.
section
Tolerance
Min. section
Tolerance
Roughness
Tolerance
Roughness
Economic
batch
Roughness
Economic batch
Documentation
Economic batch
Documentation
-- specific
Documentation
-- specific
-- general
-- specific
-- general
-- general
Process records
© MFA and DC 2007
Shape classification
Some processes can make only simple shapes, others, complex shapes.

Wire drawing, extrusion,
rolling, shape rolling:
prismatic shapes
Stamping, folding,
spinning, deep drawing:
sheet shapes


Casting, molding,
powder methods:
3-D shapes
© MFA and DC 2007
Structured data for injection moulding*
Injection moulding (Thermoplastics)
INJECTION MOULDING of thermoplastics is the equivalent of pressure die casting of metals. Molten
polymer is injected under high pressure into a cold steel mould. The polymer solidifies under pressure
and the moulding is then ejected.
Shape
Circular Prism
Non-circular Prism
Solid 3-D
Hollow 3-D
Economic Attributes
True
True
True
True
Economic batch size
Relative tooling cost
Relative equipment cost
Physical attributes
Mass range
Roughness
Section thickness
Tolerance
0.010.2 0.4 0.1 -
25
1.6
6.3
1
Process characteristics
Discrete
Prototyping
kg
µm
mm
mm
1e+004 - 1e+006
high
high
Cost modeling
Relative cost index
fx
+ links to materials
True
False
Typical uses
Injection molding is used ……….
*Using the CES EduPack Level 2 DB
Key physical factors in
choosing a shaping process
(economics always important)
© MFA and DC 2007
Unstructured data for injection moulding*
The process. Most small, complex plastic parts you pick up –
children’s toys, CD cases, telephones – are injection
moulded. Injection moulding of thermoplastics is the
equivalent of pressure die casting of metals. Molten polymer
is injected under high pressure into a cold steel mould. The
polymer solidifies under pressure and the moulding is then
ejected.
Various types of injection moulding machines exist, but the
most common in use today is the reciprocating screw
machine, shown schematically here. Polymer granules are
fed into a spiral press like a heated meat-mincer where they
mix and soften to a putty-like goo that can be forced through
one or more feed-channels (“sprues”) into the die.
Mould
Granular Polymer
Nozzle
Cylinder
Heater
Screw
No.8-CMYK-5/01
Design guidelines. Injection moulding is the best way to mass-produce small, precise, plastic parts with complex
shapes. The surface finish is good; texture and pattern can be moulded in, and fine detail reproduces well. The only
finishing operation is the removal of the sprue.
The economics. Capital cost are medium to high; tooling costs are high, making injection moulding economic only
for large batch-sizes (typically 5000 to 1 million). Production rate can be high particularly for small mouldings. Multicavity moulds are often used. The process is used almost exclusively for large volume production. Prototype
mouldings can be made using cheaper single cavity moulds of cheaper materials. Quality can be high but may be
traded off against production rate. Process may also be used with thermosets and rubbers.
Typical uses. The applications, of great variety, include: housings, containers, covers, knobs, tool handles,
plumbing fittings, lenses, etc.
The environment. Thermoplastic sprues can be recycled. Extraction may be required for volatile fumes.
Significant dust exposures may occur in the formulation of the resins. Thermostatic controller malfunctions can be
extremely hazardous.
*Using the CES EduPack Level 2 DB
© MFA and DC 2007
Finding information with CES
File
Toolbar
Edit
View
Browse
Select
Select
Table: ProcessUniverse
Subset: Edu Level 2
Tools
Search
Print
Search web
Find what?
SLS
RTM
Which table?
Processes
ProcessUniverse
+
Joining
+
Shaping
+
Surface treatment
© MFA and DC 2007
Selection of processes

Process selection has the same 4 basic steps
Step 1 Translation: express design requirements as constraints & objectives
Step 2 Screening: eliminate processes that cannot do the job
Step 3 Ranking: find the processes that do the job most cheaply
Step 4 Documentation: explore pedigrees of top-ranked candidates
© MFA and DC 2007
Selection by series of screening stages
Browse
Select
Ceramic
Search
Material
Ferrous
Hybrid
Metal
1. Selection data
Non-ferrous
Polymer
Edu Level 2: Processes - shaping
Shape
2. Selection Stages
Limit
Tree
Physical attributes
Mass range
Tolerance
Roughness
Results
X out of 60 pass
0.2
0.3 kg
0.5 mm
100 mm
Process 1
Process 2
Process 3
Process 4
Process 5
Batch size B
Graph
Circular prismatic
Non-circular prismatic
Flat sheet
etc
B1 > B > B2
………..
© MFA and DC 2007
Spark-plug insulator: translation
Insulator
Translation of design requirements
Body shell
Insulator
Function

Material class
Alumina

Shape class
3-D, hollow

Mass
0.05 kg
Design requirements

Section
3 - 5 mm
Make 2,000,000 insulators
from alumina with given

Tolerance
< 0.5 mm

Roughness
< 100 mm

shape

Batch size
>2,000,000

dimensions

tolerance and

surface roughness
Central
electrode
Constraints
Free variable
Choice of process
© MFA and DC 2007
Spark-plug insulator: screening
Insulator
Body
shell
1
2
Select Level 2: Shaping processes
Alumina
Hybrids
B-carbide
Metals
Silicon
Polymers
W-carbide
Materials
Central
electrode
Translation
Ceramics
Physical attributes
Constraints  Material class Alumina
 Shape class
3-D, hollow
0.06 kg
Tolerance
-
Roughness
-
100 m m
Mass range
Range of sect. thickness
0.04
3

Mass
0.05 kg

Section
3 – 5 mm

Tolerance
< 0.5 mm

Roughness
< 100 mm
Economic attributes

Batch size
>2,000,000
Economic batch size
3
2e6
5
mm
0.5 mm
-
Shape
Hollow, 3 D

© MFA and DC 2007
The selection: two shaping processes
Powder pressing and sintering
Powder injection molding
© MFA and DC 2007
Data organisation: joining processes
Kingdom
Family
Class
Member
Braze
Adhesives
Joining
Processes
Solder
Welding
Gas
Fasteners
Arc
Shaping
e -beam ...
Surface
treatment
Joint
geometry

Lap

Butt

Sleeve

Scarf

Tee
Attributes
Gas welding
Gas welding
Material
Gas welding
Material
Joint
geometry
Material
Joint geometry
SizeJoint
Range
geometry
Size Range
Section
Sizethickness
Range
Section thickness
Relative
costthickness
...
Section
Relative cost ...
Documentation
Relative cost ...
Documentation
Documentation
© MFA and DC 2007
A joining record*
Gas Tungsten Arc (TIG)
Tungsten inert-gas (TIG) welding, the third of the Big Three (the
others are MMA and MIG) is the cleanest and most precise, but
also the most expensive. In one regard it is very like MIG welding:
an arc is struck between a non-consumable tungsten electrode
and the work piece, shielded by inert gas (argon, helium, carbon
dioxide) to protect the molten metal from contamination. But, in
this case, the tungsten electrode is not consumed because of its
extremely high melting temperature. Filler material is supplied
separately as wire or rod. TIG welding works well with thin sheet
and can be used manually, but is easily automated.
Joint geometry
Lap
Butt
Sleeve
Scarf
Tee
True
True
True
True
Materials
Ferrous metals
True
Economic Attributes
Physical Attributes
Component size
Watertight/airtight
Demountable
Section thickness
non-restricted
True
False
0.7 - 8 mm
Relative tooling cost
Relative equipment cost
Labor intensity
low
medium
low
+ links to materials
Typical uses
TIG welding is used ……….
Documentation
*Using the CES EduPack Level 1 DB
Key physical factors in
choosing a joining process
© MFA and DC 2007
Data organisation: joining and surface treatment
Kingdom
Family
Class
Member
Anodize
Anodize
MaterialAnodize
Joining
Processes
Shaping
Heat treat
Paint/print
Surface
treatment
Attributes
Coat
Polish
Texture ...
Electroplate
Anodize
Powder coat
Metallize...
Material
WhyMaterial
treatment?
Why
treatment?
Function
of
Coating
thickness
treatment
Coating thickness
Surface hardness
Coating
thickness
Surface
hardness
Relative cost ...
Surfacecost
hardness
Relative
...
Documentation
Relative cost ...
Documentation
Documentation
Process records
Function of
treatment
 Increased hardness
 Thermal insulation
 Wear resistance
 Electrical insulation
 Fatigue resistance
 Color
 Corrosion resistance
 Texture
 Oxidation resistance
 Decoration ….
© MFA and DC 2007
A surface-treatment record*
Induction and flame hardening
Take a medium or high carbon steel -- cheap, easily formed and
machined -- and flash its surface temperature up into the austenitic
phase-region, from which it is rapidly cooled from a gas or liquid jet,
giving a martensitic surface layer. The result is a tough body with a
hard, wear and fatigue resistant, surface skin. Both processes allow the
surface of carbon steels to be hardened with minimum distortion or
oxidation. In induction hardening, a high frequency (up to 50kHz)
electromagnetic field induces eddy-currents in the surface of the workpiece, locally heating it; the depth of hardening depends on the
frequency. In flame hardening, heat is applied instead by hightemperature gas burners, followed, as before, by rapid cooling.
Function of treatment
Fatigue resistance
Friction control
Wear resistance
Hardness
Economic Attributes
Relative tooling cost
Relative equipment cost
Labor intensity
Physical Attributes
Curved surface coverage
Coating thickness
Processing temperature
Surface hardness
Very good
300 - 3e+003 µm
727 - 794
K
420 - 720
Vickers
low
medium
low
Documentation
+
links to materials
Typical uses
Induction hardening is used …..
*Using the CES EduPack Level 2 DB
Key physical factors in
choosing a surface treatment
© MFA and DC 2007
The main points
•
Processes can be organised into a tree structure containing records
for structured data and supporting information
•
The structure allows easy searching for process data
•
Select first on primary constraints
• Shaping:
material, shape and batch size
• Joining:
material(s) and joint geometry
• Surface treatment: material and function of treatment
• Then add secondary constraints as needed.

Documentation in CES, and http://matdata.net
© MFA and DC 2007
Pause for demo
© MFA and DC 2007
Exercises: Browsing processes
File
5.1 Find, by browsing, the Level 2 record for the
shaping process Resin transfer molding (RTM) in
Shaping: Composite forming. What products,
typically, is it able to make?
5.2 Find the Level 2 record for shaping process
Abrasive jet machining and cutting in Shaping:
Machining: non-conventional machining. Can it be
used to cut glass?
5.3 Find the Level 2 record for the joining process
Friction-stir welding in Joining: Mechanical welding.
How does the process work?
Edit
View
Browse
Select
Select
Tools
Search
Table:
Table: ProcessUniverse
ProcessUniverse
Subset:
Subset: Edu
Edu Level
Level 22
ProcessUniverse
+
Joining
+
Shaping
+
Surface treatment
5.4 Find the Level 2 record for the surface coating
process Metal flame spraying in Surface treatment:
Surface coating. What are its principal uses?
© MFA and DC 2007
Exercises: Searching for processes
5.5 Find, by searching, the record for the rapid
prototyping process with the trade name SLS.
What classes of material can it handle?
5.6 Find, by searching, the record for Flexible
adhesives. Which polymers are used for flexible
adhesives?
File
Edit
Browse
View
Select
Select
Tools
Search
Find what:
SLS
Look in table:
ProcessUniverse
5.7 Find, by searching, the record for Vitreous
enameling. What Functions can it perform?
© MFA and DC 2007
Exercise : Selecting shaping processes
5.8 A process is required to mold ABS components with
a solid 3-D shape in large numbers: it should be
economic at a batch size of 1,000,000 or more.
Use the CES Level 2 Shaping data-table to find
possible candidates.
Browse
Select
Search
1. Selection data
Edu
Edu Level
Level2:
2: Processes
Processes -- shaping
shaping
2. Selection Stages
 Material: ABS
(TREE stage)
 Process: Molding
(second TREE stage)
 Shape: 3-D solid
(LIMIT stage)
6
and Economic batch size > 10
(LIMIT stage)
Graph
Limit
Tree
Shape
Solid 3-D
Joining
Process
Economic attributes
Shape
Surface
Economic batch size > 10 6
Ceramic
Material
Hybrid
Metal
Results:
Polymer
Cast
Deform
Molding
Composite
Powder
Prototype
ABS
CA
Nylon
PC
PE
PP……
 Compression molding
 Injection molding, thermoplastics
© MFA and DC 2007
Exercise : Cutting CFRP sheet
5.9 A process is required to cut flat 4mm CFRP sheet
for the face-sheets of a light-weight sandwich
panel. Using the Level 2 Shaping data-table to
select it. The requirements are




Material: CFRP
Shape: flat sheet
Section thickness: 4mm
Process characteristics: Cutting
(TREE stage)
(LIMIT stage)
(LIMIT stage)
(LIMIT stage)
Browse
Select
Search
1. Selection data
Edu
Edu Level
Level2:
2: Processes
Processes -- shaping
shaping
2. Selection Stages
Graph
Limit
Tree
Shape
Flat sheet
Physical attributes
Section thickness <>4 mm
Material
Ceramic
CFRP
Hybrid
DMC
GFRP
Metal
SMC
Polymer
……
Process characteristics
Cutting processes
Results:
 Abrasive jet machining and cutting
 Band sawing
 Laser cutting
 Water-jet cutting
© MFA and DC 2007
Exercise: Joining metal sheet
Gillette “Sensor 3” razor
Browse
Select
Search
1. Selection data
Edu
Edu Level
Level2:
2: Processes
Processes -- joining
joining
2. Selection Stages
Graph
Limit
Tree
Materials to be joined
5.10. A process is required to join 0.6 mm steel blades
onto aluminum sheet carriers to form a lap joint.
Use the Level 2 Joining data-table to find them. The
requirements are




Metals
Joint geometry
Lap joint
Physical attributes
Section thickness <> 0.6 mm
Materials to be joined: metals
Joint geometry: lap joint
Section thickness: 0.6 mm
Demountable: No (X)
Function
Demountable
All done with a
LIMIT stage
The reality:
Laser spot welds
Results:




Brazing
Power beam (laser, electron beam)
Resistance welding
Rivets and staples
 Ultrasonic welding
Blades
© MFA and DC 2007
Exercise: Surface treatment of gears
Enhancing performance of gears
Browse
Select
Search
1. Selection data
Edu
Edu Level
Level2:
2: Processes
Processes -- surface
surface
2. Selection Stages
Emerson Transmission Corp
5.11. A process is required to improve the wear
resistance and fatigue resistance of steel
gears. The requirements are
 Materials: steel
 Purpose of treatment: wear resistance
fatigue resistance
 Curved surface coverage: very good
Graph
Limit
Tree
Function of treatment
Wear resistance
Fatigue resistance
Physical attributes
Ceramic
Material
Hybrid
Metal
Ferrous
Non-ferrous
Polymer
Curved surface coverage: v. good
Results:
 Carburizing and carbo-nitriding
 Nitriding
 Induction hardening and flame hardening
© MFA and DC 2007
End of Unit 5
© MFA and DC 2007