aula 6 - selecting processes

8/13/2019 Aula 6 - Selecting Processes

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New approaches to Materials Education- a course authored byMike Ashby and David Cebon, Cambridge, UK, 2008

MFA and DC 2008

Unit 6. Selectingprocesses:

shaping, joining and

surface treatment


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Outline

Processes and their attributes

Screening by attributes Selecting shape-formingprocesses Selectingjoiningprocesses Selecting surface-treatmentprocesses Exercises


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Manufacturing processes

JoiningWelding

AdhesivesFasteners

Welding

PrimaryshapingCasting

MoldingPM methods Heater Screw

Granular PolymerMould

Nozzle

Cylinder

No.8-CMYK-5/01

Injection moulding

SecondaryshapingMachining

DrillingCutting

Machining

SurfaceTreating

PaintingPolishingHeat treating

Painting


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Each family has

attributes that differ.

Family

Joining

Shaping

Surfacing

Data organisation: the PROCESS TREE

Kingdom

Process

data-table

Class

Casting

Deformation

Molding

Composite

Powder

Rapid prototyping

Member

Compression

Rotation

Injection

RTM

Blow

Attributes

Process records

RTM

Material

Shape

Size Range

Min. section

Tolerance

Roughness

Economic batch

Documentation

-- specific

-- general

Blow molding

Material

Shape

Size Range

Min. section

Tolerance

Roughness

Economic batch

Documentation

-- specific

-- general

Injection molding

Material

Shape

Size RangeMin. section

Tolerance

Roughness

Economic batch

Documentation

-- specific

-- general

Difficult !


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Shape classification

! Wire drawing, extrusion,rolling, shape rolling:

prismatic shapes

! Casting, molding,powder methods:

3-D shapes

! Stamping, folding,spinning, deep drawing:

sheet shapes

Some processes can make only simple shapes, others, complex shapes.


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Structured data for injection moulding*

INJECTION MOULDING of thermoplastics is the equivalent of pressure die casting of metals. Moltenpolymer is injected under high pressure into a cold steel mould. The polymer solidifies under pressure

and the moulding is then ejected.

Injection moulding (Thermoplastics)

*Using the CESEduPack Level 2 DB

Process characteristicsDiscrete True

Prototyping False

Economic AttributesEconomic batch size 1e+004 - 1e+006

Relative tooling cost high

Relative equipment cost high

+ links to materials

ShapeCircular Prism True

Non-circular Prism TrueSolid 3-D True

Hollow 3-D TruePhysical attributesMass range 0.01- 25 kg

Roughness 0.2 - 1.6 !mSection thickness 0.4 - 6.3 mm

Tolerance 0.1 - 1 mm

Cost modelingRelative cost index

fx

fx

Typical usesInjection molding is used """. Key physical factors in

choosing a shaping process

(economics always important)


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Unstructured data for injection moulding*

Design guidelines. Injection moulding is the best way to mass-produce small, precise, plastic parts with complexshapes. The surface finish is good; texture and pattern can be moulded in, and fine detail reproduces well. Theonly finishing operation is the removal of the sprue.

The economics. Capital cost are medium to high; tooling costs are high, making injection moulding economic onlyfor large batch-sizes (typically 5000 to 1 million). Production rate can be high particularly for small mouldings. Multi-cavity 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.

The process. Most small, complex plastic parts you pick up

childrens 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.

Heater Screw

Granular PolymerMould

Nozzle

Cylinder

No.8-CMYK-5/01



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Finding information with CES

Browse Select SearchToolbar Print Search web

File Edit View Select Tools

Find what?

Which table?

SLS

Processes

RTM

Joining

Shaping

Surface treatment

ProcessUniverse

+

+

+

Table:ProcessUniverse

Subset:Edu Level 2


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Selection of processes

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

Step 1 Translation:express design requirements as constraints & objectives

! Process selection has the same 4 basic steps


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Shape

Circular prismatic

Non-circular prismatic

Flat sheet

etc

Physical attributesMass range kg

Tolerance mm

Roughness m

Material

Ceramic

Hybrid

Metal

Polymer

Ferrous

Non-ferrous

B1> B > B

2

Batch

sizeB

Selection by series of screening stages

Browse Select Search

1. Selection data

Edu Level 2: Processes - shaping

2. Selection Stages

Graph Limit Tree

ResultsX out of 60 pass

Process 1

Process 2Process 3

Process 4

Process 5

"""..

0.2

100

0.5

0.3


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Spark-plug insulator: translation

" Mass 0.05 kg" Section 3 - 5 mm" Tolerance < 0.5 mm" Roughness < 100 m" Batch size >2,000,000

" Material class Alumina" Shape class 3-D, hollowConstraints

Free variable Choice of process

Body shell

Insulator

Centralelectrode

Make 2,000,000 insulatorsfrom alumina with given

" shape" dimensions" tolerance and" surface roughness

Design requirements

Insulator

Translation of design requirements

Function


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3

Economic attributes

Physical attributesMass range

Range of sect. thickness

kg-

Tolerance

Roughness

Shape

mm

mm

m

-

-

-

Hollow, 3 D

Economic batch size -

Materials

Ceramics Alumina

Hybrids B-carbide

Metals Silicon

Polymers W-carbide

2

Spark-plug insulator: screening

Bodyshell

Insulator

Centralelectrode

Translation

SelectLevel 2: Shaping processes1

" Mass 0.05 kg" Section 3 5 mm" Tolerance < 0.5 mm" Roughness < 100 m" Batch size >2,000,000

" Material class Alumina" Shape class 3-D, hollow

Constraints

0.060.04

3 5

0.5

100

2e6


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The selection: two shaping processes

Powder pressing and sintering Powder injection molding


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Data organisation: joining processes

Gas welding

Material

Joint geometry

Size Range

Section thickness

Relative cost ...

Documentation

Gas welding

Material

Joint geometry

Size Range

Section thickness

Relative cost ...Documentation

Gas welding

Material

Joint geometry

Size Range

Section thickness

Relative cost ...

Documentation

Attributes

Adhesives

Welding

Fasteners

Braze

Solder

Gas

Arc

e -beam ...

Class MemberFamilyKingdom

Surface

treatment

Joining

ShapingProcesses

" Lap" Butt" Sleeve" Scarf" Tee

Jointgeometry


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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, butalso 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, carbondioxide) to protect the molten metal from contamination. But, in

this case, the tungsten electrode is not consumed because of itsextremely high melting temperature. Filler material is suppliedseparately as wire or rod. TIG welding works well with thin sheet

and can be used manually, but is easily automated.

Physical AttributesComponent size non-restrictedWatertight/airtight True

Demountable FalseSection thickness 0.7 - 8 mm

Economic AttributesRelative tooling cost lowRelative equipment cost medium

Labor intensity low

Typical usesTIG welding is used """.



Joint geometryLap TrueButt True

Sleeve TrueScarf True

Tee True

MaterialsFerrous metals

Key physical factors inchoosing a joining process

Documentation


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Data organisation: joining and surface treatment

FamilyKingdom

Surface

treatment

Joining

ShapingProcesses

Class

Heat treat

Paint/print

Coat

Polish

Texture ...

Member

Electroplate

Anodize

Powder coatMetallize...

Attributes

Process records

Anodize

Material

Why treatment?

Coating thickness

Surface hardness

Relative cost...

Documentation

Anodize

Material

Why treatment?

Coating thickness

Surface hardness

Relative cost...Documentation

Anodize

Material

Function oftreatment

Coating thickness

Surface hardnessRelative cost...

Documentation

" Thermal insulation" Electrical insulation" Color" Texture" Decoration!.

" Increased hardness" Wear resistance" Fatigue resistance" Corrosion resistance" Oxidation resistance

Function of

treatment


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A surface-treatment record*

Induction and flame hardeningTake a medium or high carbon steel -- cheap, easily formed and

machined -- and flash its surface temperature up into the austeniticphase-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 thesurface 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 work-piece, locally heating it; the depth of hardening depends on the

frequency. In flame hardening, heat is applied instead by high-temperature gas burners, followed, as before, by rapid cooling.

Economic AttributesRelative tooling cost lowRelative equipment cost medium

Labor intensity low



Key physical factors inchoosing a surface treatment

Physical AttributesCurved surface coverage Very goodCoating thickness 300 - 3e+003 !m

Processing temperature 727 - 794 KSurface hardness 420 - 720 Vickers

Typical usesInduction hardening is used "..

Function of treatmentFatigue resistanceFriction control

Wear resistanceHardness

Documentation


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The main points

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.! Documentationin CES, and http://matdata.net

Processes can be organised into a tree structure containing recordsfor structured data and supporting information


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Exercises: Browsing processes

5.1 Find, by browsing, the Level 2record for the

shaping process Resin transfer molding (RTM) inShaping: Composite forming. What products,

typically, is it able to make?

5.2 Find the Level 2record for shaping processAbrasive jet machining and cutting in Shaping:

Machining: non-conventional machining. Can it be

used to cut glass?

5.3 Find the Level 2record for the joining processFriction-stir welding in Joining: Mechanical welding.

How does the process work?

5.4Find the Level 2record for the surface coatingprocess Metal flame spraying in Surface treatment:

Surface coating. What are its principal uses?





Joining

Shaping

Surface treatment

ProcessUniverse

+

+

+

Table: ProcessUniverseTable: ProcessUniverse

Subset: Edu Level 2Subset: Edu Level 2

Joining

Shaping

Surface treatment

ProcessUniverse

+

+

+

Joining

Shaping

Surface treatment

ProcessUniverse

++

++

++

Table: ProcessUniverseTable: ProcessUniverse

Subset: Edu Level 2Subset: Edu Level 2

Table: ProcessUniverseTable: ProcessUniverseTable: ProcessUniverseTable: ProcessUniverse

Subset: Edu Level 2Subset: Edu Level 2Subset: Edu Level 2Subset: Edu Level 2


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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?

Find what:

Look in table:

SLS

ProcessUniverse



Find what:

Look in table:

SLS

ProcessUniverse

Find what:

Look in table:

SLS

ProcessUniverse



5.7 Find, by searching, the record for Vitreousenameling. What Functions can it perform?

5.6 Find, by searching, the record for Flexibleadhesives. Which polymers are used for flexible

adhesives?


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Exercise : Selecting shaping processes

5.8A process is required to moldABS components with

asolid 3-Dshape in large numbers: it should beeconomic at a batch size of 1,000,000 or more.Use the CES Level 2 Shaping data-table to find

possible candidates.

" Material: ABS (TREE stage)" Process: Molding (second TREE stage)" Shape: 3-D solid (LIMIT stage)and Economic batch size > 106 (LIMIT stage)

Results:

# Compression molding# Injection molding, thermoplastics


1. Selection data

Edu Level 2: Processes - shapingEdu Level 2: Processes - shaping

2. Selection Stages

Graph Limit Tree

Process

Joining

Shape

Surface

CastDeformMolding

CompositePowderPrototype

Material

Ceramic

Hybrid

Metal

Polymer

ABSCANylon

PCPEPP!!

Shape

Solid 3-D

Economic attributes

Economic batch size > 106

Browse Select SearchBrowse Select Search

1. Selection data

Edu Level 2: Processes - shapingEdu Level 2: Processes - shaping

2. Selection Stages

Graph Limit Tree

2. Selection Stages

Graph Limit Tree

Process

Joining

Shape

Surface

CastDeformMolding

CompositePowderPrototype

Material

Ceramic

Hybrid

Metal

Polymer

ABSCANylon

PCPEPP!!

Shape

Solid 3-D

Economic attributes


Shape

Solid 3-D

Economic attributes



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Exercise: Joining metal sheet

Gillette Sensor 3 razor

5.10. A process is required to join 0.6 mmsteel blades

onto aluminum sheet carriersto form a lap joint.Use the Level 2 Joining data-table to find them. The

requirements are

" Materials to be joined: metals" Joint geometry: lap joint" Section thickness: 0.6 mm" Demountable: No (X)

All done with aLIMIT stage

Results:# Brazing# Power beam (laser, electron beam)# Resistance welding# Rivets and staples# Ultrasonic welding

Blades

The reality:

Laser spot welds


1. Selection data

Edu Level 2: Processes - joiningEdu Level 2: Processes - joining

2. Selection Stages

Graph Limit Tree

Materials to be joined

Metals

Joint geometryLap joint

Physical attributes

Section thickness 0.6 mm

Function

Demountable

Browse Select SearchBrowse Select Search

1. Selection data

Edu Level 2: Processes - joiningEdu Level 2: Processes - joining

2. Selection Stages

Graph Limit Tree

2. Selection Stages

Graph Limit Tree

Materials to be joined

Metals

Joint geometryLap joint

Physical attributes

Section thickness 0.6 mm

Function

Demountable


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Exercise: Surface treatment of gears

Emerson Transmission Corp

Enhancing performance of gears

5.11. A process is required to improve thewear

resistanceandfatigue resistanceof steelgears. The requirements are

" Materials: steel" Purpose of treatment: wear resistance

fatigue resistance

" Curved surface coverage: very good

Results:

# Carburizing and carbo-nitriding# Nitriding# Induction hardening and flame hardening

BrowseSelect

Search

1. Selection data

Edu Level 2: Processes - surfaceEdu Level 2: Processes - surface

2. Selection Stages

Graph Limit Tree

Function of treatment

Wear resistanceFatigue resistance

Physical attributes

Curved surface coverage: v. good

Material

Ceramic

Hybrid

Metal

Polymer

Ferrous

Non-ferrous

BrowseSelect

SearchBrowseSelect

Search

1. Selection data

Edu Level 2: Processes - surfaceEdu Level 2: Processes - surface

2. Selection Stages

Graph Limit Tree

2. Selection Stages

Graph Limit Tree

Function of treatment

Wear resistanceFatigue resistance

Physical attributes

Curved surface coverage: v. good

Material

Ceramic

Hybrid

Metal

Polymer

Ferrous

Non-ferrous

Material

Ceramic

Hybrid

Metal

Polymer

Ferrous

Non-ferrous

aula 6 - selecting processes

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