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TAM 302 Design for Manufacture & Assembly 1
TAM302Engineering Design Principles
Syl labus Top ic:Design for Manu factu re &
Assemble (DFMA)Int roduct ion
Course I nstructor :
Mike PhilpottDirector of Concurrent Design & Manufacture Lab
Associate Professor of Mechanical Science & Engineering
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TAM 302 Design for Manufacture & Assembly 2
$95
$10
$25
$8
$75
$100
$55
$400
$0.30
$60,000
$1.20
$5,000
x3
Piece-part costs
Tooling costs
Mfg. Alternatives:Investment/Cash Flow
Decisions
Trade off:Recurring Costs versus Non-Recurring Costs
Example: $60,000 tooling investment = $0.30 per part$5 tooling investment = $95 per part
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TAM 302 Design for Manufacture & Assembly 3
$95
$10
$25
$8
$75
$100
$55
$400
$0.30
$60,000
$1.20
$5,000
x3
Piece-part costs
Tooling costs
Mfg. Alternatives:Investment/Cash Flow
Decisions
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TAM 302 Design for Manufacture & Assembly 4
DFM: where M =Primary Mfg. Process
Select theManufacturingProcess
Improve thedesign formanufacturability
AnalyzeCost
Broad processknowledge
Comparativecost knowledge
Do's & Don'ts(Rules/checklist)
Cost-of-features
knowledge
Quote Hist. data Models Software
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TAM 302 Design for Manufacture & Assembly 5
Design ForAssembly (DFA)
Assembly typically occupiesbetween 40% and 60% of thetotal production period.
SelectAssemblyMethod
Analyze forAssembly
Improve thedesign
Manual Robotic Specialpurpose
DFA principles BDI handbook Software (BDI,Sapphire, AEM)
$
%
Combine Eliminate Simplify
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TAM 302 Design for Manufacture & Assembly 6DFAExample
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Assembly LaborHours per Car
U.S. (Big 3)
Japan
Europe
16
25
36
Data Source: Detroit Free Press
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DFA onFord Taurus
Savings resulting from the use ofDFA techniques on Ford's TAURUSCarline have been estimated to be
> $1 billion.
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NCR 2760 Point-of-saleTerminal
Assembled blindfolded at DFA conf. in 1.5 mins. Reduced number of parts by 80% Reduced number of vendors by 65% Eliminated special assembly tools Estimated lifetime labor cost redn. of $1.1 million Estimated savings from elimg. 1 screw $12,500
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Design ForAssembly (DFA)
Assembly typically occupiesbetween 40% and 60% of thetotal production period.
SelectAssemblyMethod
Analyze forAssembly
Improve thedesign
Manual Robotic Specialpurpose
DFA principles BDI handbook Software (BDI,Sapphire, AEM)
$
%
Combine Eliminate Simplify
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DFAPrinciples
A. 'Product' Design forAssemblyThe design of the entire product with a view tooverall ease of assembly.
B. 'Component' Design forAssemblyThe design of each component for ease ofassembly to its neighbors.
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A. 'Product' DFAPrinciple #1.
1. Design for minimumnumber of parts
Is there a way that reduces the number ofrequired parts?
Are all components essential or can their
functions be achieved by modifying anexisting component?
Can components be combined into one andmanufactured as an integral multifunctional
component?
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Ex. Application ofPrinciple #1.
New design= 3 parts
Old design= 8 parts
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TAM 302 Design for Manufacture & Assembly 14
Old Design = 25 parts New Design = 2 parts
Ex. Application ofPrinciple #1.
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TAM 302 Design for Manufacture & Assembly 15
2. Minimize number of
fasteners and their components Use snap fits where possible Use press fits where disassembly is not required Consider molded hinges, straps, or hook-unders Rationalize fasteners - types, lengths etc.Use one piece fasteners with lead in pilots Design geometry for automatic alignment
A. 'Product' DFAPrinciple #2.
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TAM 302 Design for Manufacture & Assembly 16
Hook-under design tominimize number offasteners
Ex. Applications ofPrinciple #2.
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TAM 302 Design for Manufacture & Assembly 17
Ex. Applications ofPrinciple #2.
Use single-piecefasteners, withguide pilots
orinserts
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TAM 302 Design for Manufacture & Assembly 18
Ex. Applications ofPrinciple #2.
Snap fits - can bedesigned for ease ofassembly &disassembly
Recess for
release ofsnap
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TAM 302 Design for Manufacture & Assembly 19
Living hinges& straps
Ex. Applications ofPrinciple #2.
Hinges, strapsand/or snap fits:
Snap fits
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TAM 302 Design for Manufacture & Assembly 20
Ex. Applications ofPrinciple #2.
Rocker-box example:Good ergonomics / style
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TAM 302 Design for Manufacture & Assembly 21
3. Design the product for
assembly from one direction Where possible assemblies should bedesigned so that a base piece is established,and remaining parts assembled from one,ideally vertical (Z) direction.
It is difficult to feed components in from theside.
A. 'Product' DFAPrinciple #3.
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TAM 302 Design for Manufacture & Assembly 22
4. Avoid the need to
turn the assembly over If previously placed components have not beenfastened, they may move out of position.
Datum and location points change, andcomplicate the assembly process, which leadsto jamming and assembly failure.
A. 'Product' DFAPrinciple #4.
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TAM 302 Design for Manufacture & Assembly 23
5. Standardize on Components,
Materials, and FastenersComponents can be difficult to differentiate,
particularly small similar shaped ones.
It is relatively common for feeders to becomejammed because wrong parts have been fedin by operators.
Considerable savings in storage, inventory,ordering etc.
A. 'Product' DFAPrinciple #5.
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TAM 302 Design for Manufacture & Assembly 24
6. Provide location surfaces that areclosely related to datum surfaces
This ensures a known location tolerance for theautomatic placing of components.
Care should be taken to avoid tolerance build-up.
A. 'Product' DFAPrinciple #6.
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TAM 302 Design for Manufacture & Assembly 25
7. Consider ease ofdisassembly for maintenance,
service, repair, and recycling Integral snap fits, press fits, and retaining clips
(circlips) allow compact designs, but if care isnot taken, result in impossible disassembly
Disassembly is frequently necessary due toincorrect assembly, the need to service/repair,and now the requirement to recycle
A. 'Product' DFAPrinciple #7.
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TAM 302 Design for Manufacture & Assembly 26
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TAM 302 Design for Manufacture & Assembly 27
8. Adopt a modular design
philosophy for the product group Allows model variations to be accomplished ata sub-system level. Subassembly volumesincrease, total parts decrease.
Modular sub-assemblies may be built andtested by specialist teams (higher quality).
A. 'Product' DFAPrinciple #8.
Modular Design
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TAM 302 Design for Manufacture & Assembly 28
Modular DesignAssembly time reduced from 540 hrs to 180 hrs
Design time per crane =350 man hrs - 18hrs
Fabrication time = 1500 hrs to 550 hrs
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TAM 302 Design for Manufacture & Assembly 29
9. Avoid the need forassembly adjustments
Eliminating adjustments will usually reduceassembly time considerably; and reduce
service / maintenance
Equipment going out of adjustment is one of
the biggest causes of customer dissatisfaction. Spring loading can be used effectively to avoidassembly adjustment and to eliminateadjustment for wear.
A. 'Product' DFAPrinciple #9.
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TAM 302 Design for Manufacture & Assembly 30
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TAM 302 Design for Manufacture & Assembly 31
A. 'Product' DFAPrinciple #10.
10. Minimize assemblysteps and extra operations
Each assembly step or operation must beresourced
Mistakes in assembly are one of the greatestcause of product malfunction and customerreturns. The fewer the steps the fewer theopportunities for error.
Extra operations such as applying grease,sealants, turning part over etc. add to time andreduce assembly efficiency.
B 'C t' D i
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TAM 302 Design for Manufacture & Assembly 32
Feeding the components: from a bin, bulkfeeder (e.g. bowl feeder), or magazine, or
continuous strips. Orienting the components: by human operator,by the feeder tracks, and by the robot /workhead.
Positioning and Placing the components
B. 'Component' Designfor Assembly
The design of eachcomponent for ease ofassembly to its neighbors;i.e. the following tasks:
B 'C t' DFA
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TAM 302 Design for Manufacture & Assembly 33
1. Components should besymmetrical or haveexaggerated assymetry
Symmetrical shapeshave a predictablerest aspect
Non-symmetrical shapes
have an unpredictableresting aspect
exaggerated assymetryand part falls on oneof its flat faces
B. 'Component' DFAPrinciple #1
B 'C t' DFA
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TAM 302 Design for Manufacture & Assembly 34
2. Components shouldhave the least numberof important directions
A
B
is betterthan
is betterthan
B
A
To reduce the chance of correctfeeding and positioning:
B. 'Component' DFAPrinciple #2
B 'C t' DFA
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TAM 302 Design for Manufacture & Assembly 35
Where possible make chamfers and lead-in anglesgenerous, and avoid sharp corners, to avoid jamming:
3. Provide Lead-in orChamfers
B. 'Component' DFAPrinciple #3
OR
B 'Component' DFA
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TAM 302 Design for Manufacture & Assembly 36
Often a small design change can eliminate thetendency of components to tangle. Close ends andkeep material thickness greater than gaps and slots:
4. Components should befree from burrs andflash, and be smooth in surface finish.
B. Component DFAPrinciple #4 & #5
5. Design parts to prevent tangling:
B 'Component' DFA
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Loosely tolerancing non-functional dimensionscan cause problemsif the feeding andorienting method is
not considered -jamming may occurif components are at extremes of limit:
Feeder / Hopper
Delivery
Tube
Parts
t
B. 'Component' DFAPrinciple #4 & #5
6. Consider the dimensionsimportant to feeding and orienting
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