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Georgia Institute of TechnologySystems Realization Laboratory
Recycling Guidelines
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Georgia Institute of TechnologySystems Realization Laboratory
Design for Recycling Guidelines
• Most recycling guidelines are divided into three categories:
– Component design
– Material selection
– Fastener selection
• Most people agree that these issues, plus the choice of whichprocesses are employed for recycling, have the largest impact
on recyclability.• Mechanical and manual separation techniques can be
suggested for each of the above areas.
• Some also emphasize packaging.
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Fundamental Lessons Learned
• As part of ongoing efforts in improving vehicle recyclability,a number of fundamental lessons have been learned from thedisassembly of vehicles and studies by the Vehicle RecyclingPartnership:
– The limiting factor in economic recycling of complex, integrated assemblies(such as instrument panels) is the separation into pure material streams.
– Both manual and mechanical separation have their advantages anddisadvantages.
– Significant value must be retained in a part for manual separation to beeconomically feasible.
– Different design techniques should be employed depending on whether onewants to facilitate manual separation or mechanical separation.
• These fundamental lessons should be kept in mind whengenerating design alternatives.
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Process Selection Guidelines
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Metric for Selecting Separation Technique
• How do you know which process to design for?
• The following flowchart provides a relatively simple metric fordesign decision support.
Hig h material remo val rate (MRR )?(ap prox. 10 lb s /min for plastics)
Manu al Sep arat ionTechn iqu es ap p lied
Rep eat fo r compo n en ts of assemb ly
Mid -v alu e b ut imp ro vab le MRR?(ap prox. 5 lbs/min fo r p las tics )
Mechanical Sep arationTechn iqu es ap p lied
No
Yes
No
Yes
can did ate desig n
Material Removal Rate = Material [kg] / time [min]From: Coulter, S. L., Bras, B. A., Winslow, G. and Yester, S., 1996, “Designing for Material Separation: Lessons from the AutomotiveRecycling,” 1996 ASME Design for Manufacturing Symposium, ASME Design Engineering Technical Conferences and Computers in
Engineering Conference, Irvine, California, August 18-22, ASME, Paper no. 96-DETC/DFM-1270.
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Detached Weight for Cost Neutral Recyling (g/min)
• The amount of material (in grams) that has to be detached perminute if recycling is to be cost neutral for manual disassembly:
– Precious metals:
» gold 0.05
» palladium 0.14
» sliver 5.1
– Metals:
» copper 300
» aluminium 700
» iron 50,000
– Plastics:
» PEE 250» PC, PM 350
» ABS 800
» PS 1000
» PVC 4000
– Glass 6000
Based on West-European hourly rates and
material prices in Sept. 1995
(Philips Center for Manufacturing Technology)
Estimated total industrial labor rate: US$0.6/min
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End-of-Life Destination Flowchart(from TNO Industry Delft, The Netherlands)
• General guidelines to determine end-of-life destinations
YES NO
r e s t f r a c t i o n s
Is productdisas sembly part of the policy?
Is the product (or partsof it) fit for mechanicalprocessing?
Which parts can beincinerated, dumped or treated as chemical waste?
Will the material cyclesbe closed?
Which parts can berecycled or reused?
Which parts will besuitable for high andlow quali ty recycling?
r e s t
f r a c t i o n s
YES
NO
Reuse High qualityrecycling
Low qualityrecycling
Incineration Landfill Chemicalwaste
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Material Selection Guidelines
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Recycling Two or More Materials(from GE Plastics)
Rule of Thumb:You want to take the
shortest path for
material recyclingNOTE: I deall y, you just want
to have ONE mater ial!
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Material Compatibility
• Compatibility matrices (or tables) listwhether two materials are compatible,that is, they can be processed together.
• Most tables are for plastics, but somealso exist for metal alloys. Most use a
(rough) scale of 1-4 or 1-3.• Typically, the information regarding
compatibility (and especially detailedinformation) is buried in chemicalhandbooks.
Additive
M a t r i x m a t e r i a l
compatible
compatible with limitations
compatible only in small amounts
not compatible
Important plastics
The table shown here is translatedfrom VDI 2243.
I n case of doubt, see your mater ial expert.
Question:
Are regular and galvanized steel compatible?
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Glass and Ceramics Compatibility
+ = good, 0 = moderate, - = poor/nil
The table shown here is from“Ecodesign: A PromisingApproach to SustainableProduction and Consumption”,UNEP/IE, United Nations.
bottle glass window glass drinkingglass
drinking glass(crystal)
TV (screen) TV (cone) TV (neck) LC D (screen) ceramics
bottle glass + - - - - - - - -
window glass + + + - - - - - -
drinking glass + 0 + - - - - - -
drinkingglass(crystal)
- - + - 0 0 - -
TV (screen) 0 0 - - + 0 - - -
TV (cone) - - - 0 - + + - -
TV (neck) - - - 0 - - + - -
LCD (screen) 0 0 - - 0 - - + -
ceramics - - - - - - - - -/0
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Compatibility of Metals
• In general, metal parts are easily recycled, but the following
rules and guidelines apply: – Unplated metals are more recyclable than plated ones.
– Low alloy metals are more recyclable than high alloy ones.
– Most cast irons are easily recycled.
– Aluminum alloys, steel, and magnesium alloys are readily separated and recycled
from automotive shredder output. – Contamination of iron or steel with copper, tin, zinc, lead, or aluminum reduces
recyclability.
– Contamination of aluminum with iron, steel, chromium, zinc, lead, copper ormagnesium reduces recyclability.
– Contamination of zinc with iron, steel, lead, tin, or cadmium reduces recyclability.
Metal
(processe d by way
of s melting
process)
Knock-out
elements
(decreases value
of the f raction to
zero)
Penalty e lements
(seriously
decrease value o f
the fraction)
Copper (Cu) Hg, Be, PCB
(polychlorobezene)
As, Sb, Ni, Bi, Al
Aluminum (Al) Cu, Fe, polymers Si
Iron (Fe) Cu Sn, Zn
The table shown here is from“Ecodesign: A PromisingApproach to SustainableProduction and Consumption”,UNEP/IE, United Nations.
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A Well Known Laminate Example
Look around and you will see a lot of room for improvement.
From:
“Green Products by Design –
Choices for a Cleaner
Environment”, Office of
Technology Assessment, US
Congress, Oct. 1992.
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Material Selection
• “At the onset of a new program, the Design Office, PlatformEngineering, Purchasing and Supply, and the component suppliershould discuss recycling issues associated with a concept anddetermine the „best fit‟ materials and processes for specificapplications.”
• “Suppliers should be encouraged to demonstrate recyclability andto take materials back for recycling at the end of the vehicle‟suseful life to be recycled in automotive and other applications.”
• “The use of materials which have been recycled, including fromold vehicles, is desirable where it is economically viable.”
(from Chrysler Vehicle Recycling Design Guidelines)
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Diversity of Plastics
• There is an incredible variety of plastics in modern vehicles.
• However, the top 7 used plastics are (in N-America)
– Urethane; 1990 - 454 mill. lbs, 1995 - ± 493 mill. lbs.
– Polypropylene (PP); 1990 - 437 mill. lbs, 1995 - ± 522 mill. lbs.
– Acrylonitrile/Butadiene/Styrene (ABS); 1990 - 281 mill, 1995 - ± 289 mill. lbs.
– Polyvinylchloride (PVC); 1990 - 264 mill. lbs, 1995 - ± 288 mill. lbs.
– Nylon; 1990 - 208 mill. lbs, 1995 - ± 246 mill. lbs.
– Polyethylene (PE); 1990 - 191 mill. lbs, 1995 - ± 248 mill. lbs.
– Polyester composite (SMC); 1990 - 173 mill. lbs, 1995 - ± 261 mill. lbs.
• Thus, if you have to choose a plastic, try picking one which iswidely used.
• Minimizing material diversity is beneficial for acquisition,storage, manufacturing, recycling, etc.
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Main Material Concerns
• Meet environment, health, and occupational safety requirementsfor regulated or restricted substances or processes of concern.
– Do not, or limit, the use of materials which pose human or environmental risk.
• Mark materials according to standards.
• Generate minimal home and pre-consumer scrap duringmanufacturing.
• Make components of different recyclable materials easilyseparable, or use materials which can be recycled as a mixture.
• Standardize material types.
• Reduce painting.
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Cathode Ray Tubes - Problem
• Cathode ray tubes (CRTs) pose a major difficulty forrecycling.
• The phosphor-based coating used to provide the necessaryluminescence contains heavy metals and other toxins, while
the glass itself is loaded with lead and barium.
• Recycling a specific design of CRT with known constituentsis relatively straightforward, but finding a process that willhandle very large quantities of CRTs of varying age andspecification is not so easy.
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Marking of Plastics
• SAE J1344 – April 1993 contains the standards on markingof plastic parts.
• Based on standard symbols as published by ISO 1043.
• Allows for expansion and inclusion of new symbols for newmaterial. (complete appropriate forms).
• See SAE J1344 for examples and specifics.
•European legislation wil l requir e the marking of all plastic parts with a weight greater than 100 grams.
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Positions and Life of Markings
• No position of marking is prescribed, but: – Field service people should be informed regarding the material.
– If practicable, marking should be located where it may be observed while it isin use. May consider multiple markings.
– Marking on the outside is preferred for field service people.
• Also, markings should last: – Markings applied with inks, dyes, paints should not bleed, run, smudge, or
stain materials in contact with the marking.
– Markings should be designed to remain legible during the entire life of thepart.
– Markings which are molded into the part are preferred since they are
permanent and do not require additional manufacturing operations. BUT,molded parts should not create a stress concentration.
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Material Selection – Summarizing
General:
• Avoid regulated and/or restricted materials
– These often MUST be recycled, whatever the monetary cost of removal is.
• Use recyclable materials
– Both technically as well as economically
• Use recycled materials, where possible – This increases recycled content
• Standardize material types
– May involve corporate decision
• Reduce number of material types
– Can be done at engineering level
• Use compatible materials, if different materials are needed.
– Single material is preferred, however.
• Eliminate incompatible laminated/non-separable materials.
– These are a major hassle.
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Material Selection (cont.)
Manual Separation:
• Avoid painting parts with incompatible paint
– Especially plastics can be contaminated by paint.
• Eliminate incompatible laminated/non-separable materials
Mechanical Separation:
• Reduce number of materials as much as possible
– Probably two materials can be economically recovered
• Choose materials with different properties (e.g., magnetic vs
non-magnetic; heavy vs light), thus enabling easy separation.
• Allow for density separation
– Maintain at least 0.03 specific gravity difference between polymers
– Isolate polymers with largest mass by density
• Eliminate incompatible laminated/non-separable materials
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Component Design Guidelines
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Component Design
• Apply Design for Manufacturing and Assembly (DFMA)and Serviceability Guidelines as appropriate in componentdesign.
– Facilitate ease of assembly removal and material separation.
– (There is a close correspondence between DFA, DFD, and Design for
Service)
• Route wiring to facilitate removal.
Pins are easy to tap outDifficult toremove
Pressedalignment
pins
Pressed boltsand studs
Complete holesPay attenti on to detail and
reduce the amount of
frustration and special
equipment.
Label dangerous operations.
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Minimize Part and Material Count
• To facilitate separation and collection:
– Minimize the number of components within anassembly.
– Minimize material types within an assembly.
– Build in planes of easy separation where this doesnot affect part function.
» Look under a hood for good and bad examples.
– (By the way, think also about modular i ty)
Question: What other (non-DFR) reasons exist for minimizing part and mater ial count?
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Classical Component Integration Example
• Springs and their support systems are always classicalexamples of component integration.
• Note the reduction in part and material count.
a) b)
a) Traditional design of springs in a doorlock:different materials, e.g., steel, aluminum
b) Injection molded spring sys tem made from POM(single material product)
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Laminates and Paints
• Avoid laminates which require separation prior to reuse.
– Even though unique separation techniques exists, it increases the cost of therecyclable material.
– When laminates are used, design them from compatible materials and adhesives.
Examples :
– Dashboard cover:
» Old design: PVC top foil, PUR foam core, steel support plate
» New design: PP top foil, PP foam core, support layer of PP
– Bumper:
» Old design: PC skin, PUR foam core, steel support
» New design: Integral foam of PC, PP, support frame of PC, PP
• Avoid painting parts wherever possible.
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Problems with Paints
• In general, paints contaminate plastics to be recycled. – Compatible paints exists, but the majority is non-compatible.
– One percent (!) of contamination can be enough to ruin a plastic batch forrecycling.
• Many painting processes are subject to regulations. – For example, in case a city-wide smog alarm goes off, certain paintingprocesses (or other processes with volatile compounds) need to be stopped.
• Stripping paint is also a very nasty process.
– Environmentally benign stripping processes exists, but the paint chips still
have to be disposed off.
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Component Design - Summarizing
General:
• Integrate parts
– Reduce disassembly time
• Minimize scrap during production
Mechanical separation:
• Avoid using incompatible materials
– E.g., stiffen sections rather than adding foam for noise-vibration-heat areas
Manual:
• Use Design for Manufacturability/Assembly and
Serviceability guidelines• Reduce number of steps to remove a recyclable part
• Reduce chance of contamination
• Route wiring to facilitate removal
– Separate at bulkheads/interface areas
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Fasteners –
Guidelines
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What about fasteners ?
• In VDI 2243, an example is given on the remanufacture of a four cylinderinternal combustion engine.
• About 32.5% of all activities in the disassembly process consist of theloosening of screws. These activities consume 54% of the entiredisassembly process time.
• According to VDI 2243, this is a typical example.
• The separation of staple, glue, press joints or joints made by deformationnot only require more specialized equipment, but also embody a higher
risk of damaging the component, if it is to be reused.
• Additional problems occur when contaminations such as oil, dirt andcorrosion are present.
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Assembly and Disassembly
• Adhere to Design for Assembly guidelines – Good designs take ease of assembly as well as service and recycling into
account.
• Facilitate disassembly (Design for Disassembly)
– Select fasteners which facilitate disassembly by any method includingdestruction (by shredding) after a vehicle‟s useful life.
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Reduce and Commonize Fasteners
• Reduce the number and types of fasteners used.
• Select fasteners that do not require post-dismantling materialseparation for recycling.
– When practical, use fasteners of the same (or compatible) material as theattaching part.
– If this is not possible for plastic fasteners, use ferrous fasteners or inserts to allowfor magnetic separation after shredding.
• Commonize fasteners
– Try to design with minimum screw head types and sizes. (remember theVolkswagen Bug‟s 13 mm wrench standardization)
• DO NOT JEOPARDIZE STRUCTURAL INTEGRITY OR FUNCTION !!
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Select Proper Coatings
• Corroded fasteners cause severe problems for fast removal of parts
• Select coatings which minimize corrosion.
– This may drive up the cost.
– Phospate & oil coatings have low corrosion resistance
– Better (but more costly) coatings may be warranted for recyclability (andservicability).
• Cadmium coatings should not be used because of potential
health and environmental hazard.
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Snap fits
• Use snap fits wherever possible to reduce the use of additional fasteners.
• Molded clips should be removable without breaking off.
IMPORTANT:
• Do not jeopardize product integrity.
• Also, consider long term effects (hardening of plastic,fatigue failure, frustration of broken snaps).
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Adhesives
• Joining or bonding materials of the same type withcompatible adhesives enhances recycling.
• But, non-compatible adhesives may cause contaminants toenter the material waste stream.
• Therefore, adhesive selection and the effect on partrecyclability should be discussed with Materials Engineeringas part of the development process at the onset of a program.
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VDI 2243’s Fastener Selection Table
• This table gives an overview of a German rating of fasteners.
• It will give you an idea of how different fasteners compare against each other.
• Caution: By no means is thi s a defini te table!
characteristics
of connection
principle
of connection
Static St rength
Fatigue
Strength
Joining
Expenditure
Guidance
Expenditure
Detaching
Expenditure
Destructive
Detaching
Expenditure
Product
Recycling
Material
Recycling
C a r r y i n g
C a p a c i t y
J o i n i n g
B e h a v i o u r
D e t a c h i n g
B e h a v i o u r
R e
c y c l a b i l i t y
good average bad
plastic/metal
adhesive
bonding weldingmagnetic
connection
Velcro
fastener
bolt/
nut
plastic
bolt/
nut
spring
connection
snap
joint
bent-lever
connection
1/4-turn
fastener press-turn
fastener
press-press
fastener band with
lock
Material Connection Frict ional Connection Positive Connection
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Fastener Selection – Summarizing
Clear distinction between manual vs mechanical separation guidelines
Manual Separation: • Reduce number of fasteners
• Commonize fastener types
• Use fasteners made of compatible materials
• Consider snap-fits (two-way, if necessary)• Consider destructive fastener removal
– Possible inclusion of break points in material
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Fastener Selection: Mechanical Separation
IMPORTANT: Fasteners wil l not be unfastened! – Disassembly time is irrelevant!
Material properties are (again) key issue
In order of preference, use
1) Molded-in fasteners (same material)
2) Separate fasteners of same or compatible material
3) Ferrous metal fasteners (easy to remove due to magneticproperties)
4) Non-ferrous metal fasteners (can be removed using, e.g.,Eddy-current)
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Trade-offs
• Design for Recycling can negatively affect performance andcost issues.
– For example, required material substitution is not always possible or will costmore.
• However, in most cases, the trade-offs can be resolved andoften converted in win-win situations.
• Often cited and studied and questioned are the trade-offsbetween design for disassembly and design for assembly.
• Take a look at the DFA guidelines and compare them not justwith DFD, but also with DFR in general.
– Remember, a shredder does not care much about geometry and fasteners…
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Product Design for Assembly Guidelines
Product Design for Assembly
1) Overall Component count should be minimized.
2) Minimum use of fasteners.
3) Design the product with a base for locating other components.
4) Do not require the base to be repositioned during assembly.
5) Design components to mate through straight-line assembly, all from thesame direction.
6) Maximize component accessibility.
7) Make the assembly sequence efficient.
- Assembly with the fewest steps.
- Avoids risks of damaging components.
- Avoids awkward and unstable component, equipment, and personnelpositions.
- Avoid creating many disconnected subassemblies to be joined later.
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Component Design for Assembly Guidelines
Component Design for Assembly
8) Avoid component characteristics that complicate retrieval
(Tangling, nesting, and flexibility)
9) Design components for a specific type of retrieval, handling, and
insertion.
10) Design components for end-to-end symmetry when possible.
11) Design components for symmetry about their axes of insertion.
12) Design components that are not symmetric about their axes of insertion to be clearly asymmetric.
13) Make use of chamfers, leads, and compliance to facilitate insertion.
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DFR – Special Issues
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Limiting Factors
• Identify the limiting factors and address these first!
• Look at a combination of the following component aspects: – Weight – If recyclability and recycled content are defined by weight, it makes
sense to look at the heaviest components first. Improving a 10 pound component‟srecyclability rating from 4 to 3 has a larger impact on the overall systemrecyclability than improving a 1 pound component.
– Distance from target ratings – Components with recyclability ratings of 4 and
lower should be improved. Pay special attention to components with arecyclability rating of 4 because they can often relatively easily be changed toobtain a (good) rating of 3. The same applies for material separation ratings, i.e.,first focus on those components with a separability rating of 4.
– Risk – Those components with a high risk are also prime candidates forimprovement.
– Violation of Design for Recycling guidelines – A component which clearly violatessome of the Design for Recycling guidelines may also be a limiting factor and aprime candidate for improvement. Pay special attention to WHY one or moreguidelines have been violated; it may have been done intentionally to, say,increase functionality or manufacturability.
• Often, upon careful inspection, the material or combination of materials is the limiting factor in most parts.
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Risk Assessments
• Some basic simple risk assessments with respect to achieving
targets can be doneRisk Low Medium HighRecyclabilit y % Recyclability
identified and
meets initial
t argets. Planned
changes will not
degrade it .
% Recyclability
does not meet
initial target s, but
plan ned changes
provide
improvements.
1) % Recyclability
does n ot meet
initial target s
and/or p lanned
changes do not
provide
improvement s.2) % Recyclability
meets initial
t argets, but
plan ned changes
degrade it below
target level.
Recycled Co ntent Recycled co nt ent
identified and
meets initial
t argets. Plannedchanges will not
degrade it .
Recycled cont ent
does not meet
initial target s, but
plan ned changes provide
improvements.
1) % Recycled
content does not
meet initial targets
and/or p lannedchanges do not
provide
improvement s.
2) % Recycled
content meets
initial target s, but
plan ned changes
degrade it below
target level.
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Management Issue: Recyclability Target Setting
• Goal of designer: Improve vehicle recyclability – 85% (by weight) required recyclability in 15 years
• Current recyclability (first revision) 75%
• Four (yearly) revisions of vehicle expected
• Data available on: – expected production for each year
– estimated reliability of vehicles
• Aim: Aid designer in setting appropriate targets for the
recyclability of each revision of the vehicle
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Target Setting: Parameters
• Production Uncertainty: Normal, = 5,000
• Recyclability: Triangular, ± 3%
• Reliability, Weibull distribution
• Monte Carlo simulation used to explore effects of a given set
of targets
Iteration Mean EstimatedProduction
Mean EstimatedRecyclability
EstimatedReliability
1 100,000 75% =7, =11
2 95,000 TBD =7, =113 95,000 TBD =7, =11
4 90,000 TBD =7, =11
5 90,000 TBD =7, =11
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Target Setting: Constant Improvement
Iteration 1 2 3 4 5Recyclability Target 75% 78% 81% 84% 87%
Recyclability of Vehicles Retired in a Given Year
Certainties Centered on Medians
0.700
0.750
0.800
0.850
0.900
90%
5%
Trend Chart
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Target Setting: Achieving 85% Recyclability
Iteration 1 2 3 4 5Recyclability Target 75% 80% 84% 87% 89%
Recyclability of Vehicles Retired in a Given Year
Certainties Centered on Medians
0.700
0.750
0.800
0.850
0.900
90%
5%
Trend Chart
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Inclusion of Uncertainty
• How will changes in technology and legislation affect thetarget definition and prioritization of limiting factors?
legislative limit
product’smeanenvironmentalimpact
Environmental Impact
Initial Product
Range of Expected Regulatory Limits atIteration 5 (one-sided distribution)
Iteration 2
Iteration 3
Iteration 4Iteration 5
Reduction of mean environmental i mpact and variance over several iterati ons
Y
Xcompliance high
legislative mean
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Computer-Based Tools
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Computer-Aided Design for the Life Cycle System Architecture
ProductModeling
Synthesis & SelectionCAD
Ev aluation Modules
ProblemFormulation
AssemblyModeling
Manufacturing
Recycling
Disassembly
Robustness
Imp rovement
Models
Parametric Assemb lyModel
Geo metry Life-CycleInformatio n
Database of P roductRepresentations
Service
Compa risonModels
Graph ics
Parametrics
Geo metry
Features
Materials D B
Facilities D B
Features,Components, &
Mati ng RelationshipsDB Process DB
Designer
Design System
ProcessModeling
Process Synthesis &Selection
Ev aluation Modules
Simulatio n
Imp rovemen tModels
Compa risonModels
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Automotive Center Console
• Given are the geometric(solid) and assemblymodels of a center consoledesign generated using amodern CAD package.
Rightbase
Leftbase
Endcap
BinFront bracket
Bezel Ashtray Latch Armrest
Hinge
Coverplate
Assembly ModelCenter Console
Base Armrest Ashtray &
Lighter
Cupholder
Bin
Leftbase
Rightbase
Bezel
Endcap
Solid Model
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Virtual Disassembly
• Disassembly in a Virtual
Reality environmentfacilitates design forrecycling as well as designfor serviceability.
– Other assessments are also beingadded (e.g., demanufacture
process cost assessments)
• The key is to use theexisting product modelsand add functionality inexisting and (for a
designer) familiarsoftware systems.
NSF grants:
– Virtual Design Studio for Servicing and Demanufacture (Rosen, Bras, Mistree, Goel, Baker) – DMI9420405
– CAD for De- and Remanufacturing (Bras and Rosen) – DMI9414715
– Enhancing Reusability by Design (Bras) – DMI9410005
– Integrated Product and De- and Remanufacture Process Design (Bras) – DMI9624787
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Kodak Funsaver Virtual Disassmbly
Hand int erface
Camera
components
• Virtual disassemblyallows tracking of basic disassembly pathbased on user/designerexperience.
• This path can be fine-tuned using othertools.
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IGRIP Robotic Disassembly Simulation
Disassemblycycle times arecalculated.
Disassembly paths are
simulated and tested.
Different robots can be simulated and programmed
Detailed information about the kinematic and dynamic behavior of the robot can be obtained