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Lecture 2 Selecting the

manufacturing processes

Final Design

Preliminarydesign

Material selection

ManufacturingProcess

Selection

Ideageneration

FeasabilityStudy

ProductFessible

?

DFA

DFEDFM

Yes

No

Proto type

Design Process

Preliminarydesign

• Function (what does the component do)

• Objective (what is to be maximized or minimized)

• Constraints(what essential conditions to be met)

• Free variables (which design variables are free)

Design Requirements

• Functional drawing, flowcharts, sketches

• Rough component sizing

Design Concept

• Stresses, size, shape, thickness, …etcDesign

Calculations

components function?

Källa: Volvo

Källa: Volvo

Linkarm

Check for DFM and DFA

• DFA

– how easily things can be assembled

– DFA: Design of components taking into account how

they will be assembled together to ensure that assembly

costs are minimized.

• DFM – how easily things can be made

– DFM: Design of components taking into consideration

the processes that will be used to manufacture them to

ensure that manufacturing costs are minimized.

• DFMA – balance between ease of making & assembly

DFA Example:Design Simplification

•Link between function and required properties Define a “performance index” as strength (Ashby Maps)

Performance

ProcessingCharacteristics

•Process costCost

-Weldability

-Machinability

.Material selection

Data organisation

ManufacturingProcess

Selection

Material-Process

compatibility

Size-Process compatibility

Shape-Process compatibility

Cost

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Sand casting

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Die casting

Investment casting

Low pressure casting

Forging

Extrusion

Sheet forming

Powder Methods

Electro machining

Conventional

machining

Injection molding

Blow molding

Compression

molding

Rotational molding

Thermo molding

Polymer casting

Resin-Transfer

molding

Filament winding

Lay-up method

Vacuum bag

processes can be split up into:

shaping: e.g. forging, rolling, casting, blow moulding, vacuum forming

Finishing: e.g. grinding, drilling

Joining: e.g. soldering, gluing

Material-Process compatibility

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AdhesivesWelding, metalsWelding, polyemrsFaseners

Fin

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Precision machiningGrindingLappingPolishing

Metal

Ceramics

Polymers

Polymer foams

Composites

Size-Process compatibility

Can we make something this size? For instance, you can't die-cast an engine

block - it's too big.

Is the processes suitable for the shape we need? For example: tubes are long and

thin so ideal for extrusion but not casting; and you can't blow-mould a telephone

case because of all the holes in it!

Will we get the finish we want? Both dimensional tolerance (accuracy) and

surface roughness (smoothness) are strongly influenced by which process is used,

for instance sand casting is poor for both whilst die-casting is very good.

How good will the quality be? This is the most difficult problem to address and

usually there is little that can be said without actually trying it! However, we can

sometimes make rough comparisons - for instance sand castings can often be

porous and so might not be very strong.

Sand casting

Die casting

Investment casting

Low pressure casting

Forging

Extrusion

Sheet forming

Powder Methods

Electro machining

Conventional machining

Injection molding

Blow molding

Compression molding

Rotational molding

Thermo Forming

Polymer casting

Resin-Transfer molding

Filament winding

Lay-up method

Vacuum bag

10-3 10-2 0.1 1 10 102 103 104Mass (kg)

Shape-Process compatibility

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Sand casting

Die casting

Investment casting

Low pressure casting

Forging

Extrusion

Sheet forming

Powder Methods

Electro machining

Conventional machining

Injection molding

Blow molding

Compression molding

Rotational molding

Thermo Forming

Polymer casting

Resin-Transfer molding

Filament winding

Lay-up method

Vacuum bag

Weight of the disk is 5,0kg.

Ex choose a manufacturing process for the brake disk