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SAE TECHNICAL
PAPER SERIES
2002-01-2246
Design for Automotive Glass Removal Using
Active Disassembly
Nicholas Jones, David Harrison, Joseph Chiodo and Eric Billett
Brunel University, Department of Design
Reprinted From: Proceedings of the 2002 SAE International Body Engineering Conference
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2002-01-2246
Design for Automotive Glass Removal Using
Active Disassembly
Nicholas Jones, David Harrison, Joseph Chiodo and Eric Billett
Brunel University, Department of Design
Copyright © 2002 Society of Automotive Engineers, Inc.
ABSTRACT
Active Disassembly is a well researched technique for
creating assemblies or casings that can break
themselves apart for recycling using a heat trigger.
'Chiodo' has applied this principle to consumer electronic
goods since the mid nineties. In response to pending
EU legislation, the scope of active disassembly has
broadened to include automotive disassembly. The first
automotive demonstrators produced have been to make
self-disassembling window glass retaining channels that
enable easy glass removal for recycling. This waste
glass can then be used in coastal defences as an
alternative to landfill. Both shape memory alloy and
shape memory polymer solutions have been examined.
The shape memory alloy solution has been successful.
Optimisation for the polymer solution is required.
to a minimum of 85% by an average weight per vehicle
and year. For vehicles produced before 1980, the
member states may lay down lower targets, but not
lower than 75% for reuse and recovery and not lower
than 70% for reuse and recycling [1].
Ferrous metal (65%)
Non-ferrous metal
(8%)
Glass (3%)
INTRODUCTION
The pending End of Life Vehicle legislation (ELV) states
that by 2006, at least 85% of a vehicle must be reused
or recycled, rising to 95% by 2015 [1]. In order to meet
this quota vehicles will need to be dismantled and sorted
further than they have ever been before. The majority of
a vehicles mass comes from its ferrous metal content,
and this is readily recovered, leaving the lighter material
fractions for recovery {Figure 1}. As up to 2% of a
vehicles weight comes from its glass content- attempts
will be made to remove the glass and sort it. However,
as there is no market for used automotive glass [2]where will it go?
PENDING LEGISLATION - The ELV directive is a
pending piece of EU legislation that states that by 2006,
a minimum of 85% (by mass) of any motor vehicle must
be re-used1 or recovered2 when the end of life condition
arrives [1]. Within the same time limit the reuse and
recycling shall be increased to a minimum of 80% by an
average weight per vehicle per year. By no later than
2015, this quota will rise to a minimum of 95% for reuse
and recovery and the reuse and recycling level will rise
Tyres (3%)
Other rubber (seals
& hoses etc. 4%)
Thermoplastics (8%)
Other(3.5%)
Fluids(1%)
Battery (1%)
Figure 1.
Polyurethane seat
foam (2%)
Thermoset plastics
(1.5%)
Material composition of a typical 1990's
European Car (Source: ACORD)
1, Reuse.
Reused components such as engines,
alternators, starter motors and radios. These are not
recycled by complete dismantling, but by cleaning and
preparing the parts for re-sale
2, Recovery. Material recovery for recycling. This
requires each specific material (including plastic type) to
be separated for reprocessing into raw material
Meeting the Criteria - It is already established that the
automotive industry achieves a recycling rate of
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approximately 75% (by mass) with regards to ELV's.
This recycling percentage is higher than for any other
industrial sector [3]. This is due to the fact that the
majority of the weight in a vehicle is from its steel
content, and this is relatively easy to sort {Figure 1}. A
shredded vehicle is simply magnetically sorted to
separate the scrap steel, and this is fairly effective.
There must be an emphasis placed on carefully sorting
different materials from within the scrap steel stockpile to
avoid a build up of 'tramp' elements.
In particular,
copper contamination must be avoided, but this will not
be dealt with within the scope of this paper [see ref.4].
Where the problem lies, is in 'finding' the extra 10 % of
recyclate to meet the 2006 criteria. Approximately 1% of
a vehicles weight is from the battery, and this can be
removed easily for reprocessing and reuse.
Approximately 1% of the weight of a vehicle comes from
the fluids contained within the vehicle. These can be
removed by drilling the sump, gearbox and petrol tank
and sucking out the fluids and containing them
separately. Even the shock absorber fluid, coolant,
hydraulic fluids and screen wash can be removed and
contained for reprocessing. These fluids and the battery
have to be removed under the new legislation
regardless. It is compulsory to remove any hazardous
materials so that shredder residue does not get
contaminated [5]. Tyres will also have to be removed
under the European Landfill Directive (app. 3% by
mass). From 2003 it will be prohibited to landfill whole
tyres, and from 2006 the ban will also apply to shredded
tyres [6]. However, it is expected that the UK will delay
this implementation.
Unfortunately this results in a total recovered mass of
less than 80% (~79%).
With glass making up
approximately 2% of the overall weight of a vehicle, this
will be a material chosen for removal to help meet the
criteria. With 8-9 million tonnes of waste generated from
scrap vehicles across the community annually, this could
lead to around 180,000 tonnes of waste glass generated
annually that has to have a destination other than
landfill. The problems are that firstly the glass is difficult
to remove, and secondly, there is no second use for
waste automotive glass, so landfill appears to be the
only economic option.
Glass Retention - Glass is difficult to remove
completely without breakage. Avoiding breakage is
critical in helping to meet the criteria, as it is not efficient
usage of time to try and sweep out all the broken glass
fragments.
Where windscreens used to typically be
retained by rubbers and chrome glamour strips; a
modern screen is retained by a single part polyurethane
adhesive which allows the screen to contribute to the
chassis stiffness [7]. It is a similar story with regards to
rear screens and fixed quaterlight windows. However,
door windows that are 'windable' are not retained in this
way. Typically the glass is captured in a folded steel
channel that is lined with a rubber strip. This traps the
glass securely due to the crimping force of the steel
channel and the surface friction of the rubber. The
rubber is also coated in an adhesive. The steel channel
also incorporates the fixing for the winding mechanism
{Figure 2}. The steel channel is not removable from the
glass and is not available as a spare part. When a
separate door glass is purchased, the steel strip is
included. For recycling purposes it is desirable to
separate the glass from the steel strip for material
separation reasons. At present however, breaking the
glass is the easiest way to remove it from the channel.
By incorporating some "Active Disassembly" principles
at the design stage, it can be made possible to easily
remove the glass by using simple heat triggers.
Figure 2.
Ford Door Glass Retaining Channel
(250mm scale)
ACTIVE DISASSEMBLY
Active Disassembly using Smart Materials (ADSM) is
now a well proven concept that has been developed by
Chiodo at Brunel University since the mid nineties. The
principle involves incorporating actuators or releasable
fastening solutions into host products to aid disassembly
when the end of life condition arises. Initially the project
scope took in consumer electronic products [8], but now
with the ELV directive pending, the project scope has
expanded to take in automotive disassembly.
By incorporating actuators into a host product, the
product casing can be made to forcibly separate under a
heat trigger, allowing the internal components to be
recovered. These actuators have typically been made
from shape memory alloys (SMA) such as Copper/
Zinc/Aluminium, or Nickel/ Titanium. These can be
formed into tiny actuators with no additional moving
parts. For example, looking like a coiled spring, they
can sit totally inert inside a product casing and will
reliably extend under a certain temperature stimulus
{Figure 3}. As a broad summary, SMA's can exist in
two different shapes, and these can be switched by
heat. The resultant shape change is known as the
Shape Memory Effect (SME), and in the case of SMA,
there is a significant force associated with the SME. It is
this force that can be used to break assemblies. As
SMA devices are able to 'do work', they can be used as
a replacement for motors and solenoids- and they are
typically 1000 times lighter than a comparable solenoid
[9]. A solenoid is essentially another type of actuator
that could be used to facilitate active disassembly.
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Figure 3.
Phillips Radio Split With
Cu-Zn-Al Actuators [12]
SMA materials can be classed as either one-way or twoway devices. Two-way devices will return to their
original shape upon cooling, where a one-way device
will not. The extent of deformation, the material, and the
extent of the stimuli all have a bearing on the degree of
two-way behaviour shown [10]. One-way devices can
be cycled many times, but they have to be physically
bent back into their initial position for them to cycle again
[11]. In fact, SMA devices have been found to cycle
reliably millions of times so they can be safely re-used.
It should also be pointed out that SMA devices are not
bimetallic devices, this is a popular misconception. The
shape change that occurs in a SMA device is due to a
change in the alloy crystalline structure (from martensite
to austenite), not a differential expansion rate of two
differing materials.
Alternative active disassembly solutions have been
engineered around shape memory polymers (SMP) [12].
Shape memory polymers are different to shape memory
alloys in that instead of being able to exert a force when
the shape memory effect (SME) occurs, they lose all
their mechanical properties and if allowed, recover a
pre-formed shape.
SMP's have been successfully
utilised in many ways including screws that lose their
heads under thermal load {Figure 4}, screws that retract
their thread when heated and allow the screw to drop
out, and shape memory rivets. As there is no force
associated with the shape change of SMP, springs are
often used to aid product separation. A good example of
this lies with the SMP snap-fit. This is a conventional
cylindrical shaped snap fit as used on many product
casings. In this instance, the snap fastening is made
from SMP, with a biasing spring loading the joint. This
fixing then remains inert in the product. When the joint
reaches the glass transition temperature (Tg) the SMP
loses all its integrity, and the force of the spring takes
over, separating the joint and pushing the product casing
apart.
Figure 4.
Shape Memory Polymer Property Loss Screws.
These have been gravity cast using a two-part polymer
compound.
Once removed from the sprue, these screws can be
used to assemble product casings. A spring inside the
casing pre loads the screw so that when it is heated the
screw will lose its head, facilitating disassembly
Shape memory polymer is a material that has been
developed by Mitsibishi Heavy Industries, and is still
very much in the development stages. Currently only
low Tg materials (app. 60 0c) have been developed
commercially. Higher Tg materials have been produced
under lab conditions [13].
ACTIVE DOOR GLASS REMOVAL
Door glass is retained in pressed steel channels. These
steel channels are crimped to a slip of rubber that holds
the glass. The channel itself is bolted to the window
winding mechanism. Although wind-up windows still
exist, most cars now incorporate power windows,
particularly at the front. By allowing easy glass removal
from the winding mechanism, not only is it possible to
sort the glass for recycling or recovery, but it is possible
to easily remove the whole window winder assembly for
recycling or reuse. A winder mechanism typically
weighs about 1.5 kg, (1995 Ford Escort Ghia), there is a
total of 6kg (4 mechanisms) of easily recoverable
material. New glass can simply be re attached to an
existing winder mechanism.
SHAPE MEMORY POLYMER SOLUTION - To
incorporate active disassembly into the door glass area,
the crimped channel must be redesigned without
compromising the existing vehicle specification. In the
first series of experiments, the rubber slip that sits in the
steel channel was replaced with a shape memory
polymer slip. This slip was crimped to the glass in the
same way that the rubber channel was retained. This
means that there is significant pressure applied to the
polymer strip to retain the glass {Figure 5}. The system
was assembled and tested for its release properties. It
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was found that upon heating, the SMP strip would
'spread' under the small area where high pressure was
applied. This would decrease the loading on the glass,
allowing it to pull free. The Active Disassembly concept
here was a success.
the window was wound up and down. Due to the high
transition temperature of the Ni-Ti clips (120 0c), the part
also meets the Ford specification for the assembly [15].
Figure 6.
Figure 5.
Shape memory Polymer Retaining Slip
Holding Glass in a Steel Channel
Upon assembling the winder assembly and testing it
within the door, it was found that the window seal had
enough friction to pull the glass out of the channel. This
test was therefore a failure. However, shape memory
polymer is a PU based material, and the SMP samples
we have to work with are very hard in their glassy state.
According to Winfield Polyurethane, it is possible to
formulate polyurethane with hardness and surface
frictions that can replicate all but the softest rubber (PU
down to Shore A/ 20 where rubbers can be formulated at
Shore A/ 10) [14]. With further development, SMP
should be able to replicate the Shore A/ 65 used in the
steel channel rubber slip. Also, with regards to meeting
the existing part specification, the SMP solution is again
not ideal. Ford is looking for a temperature specification
of 105 0c, and as yet, there are no SMP materials that
meet this criteria.
SHAPE MEMORY ALLOY SOLUTION - The
second solution that was developed involved the use of
SMA clips. The crimped steel channel had three 8mm
slots milled to a depth on 10mm. These slots ran
perpendicular to the glass channel and were evenly
spaced. The glass was pushed into the channel in a
standard rubber slip. This time however, the channel
was not crimped but simply incorporated a small lead-in
to aid assembly. The assembled rubber and glass was
a tight sliding fit into the channel. Once in place, small
SMA clips were crimped through the milled slots so that
the rubber squeezed the glass tightly {Figure6}. The
glass could not then be pulled out, as the clips would
interfere with the channel. When heated, the clips
unrolled and dropped off the assembly. The glass could
then be slid out of the assembly, leaving the winder
assembly in the door. Active disassembly was a
success.
The SMA solution was also a success for the
reason that the glass remained firm in the channel when
Shape Memory Clips, With Parts and Dedicated
Channel (250mm scale)
Glass Reuse -
Once the glass is released, in
accordance with the ELV directive, the material must be
recycled or reused. Reuse will not be practical due to
the level of sorting required. However, the glass will still
have to be sorted carefully into differing colours for
recycling. The quality of cullett (granulated glass)
supplied for recycling has to conform to specifications
regarding colour, to avoid introducing impurities into the
melt [16].
The UK already has a good tendency to recycle glass in
bottle banks and from household waste. With the
amount of glass produced in the UK that is recycled,
coupled with the level of imported glass that also makes
it into our recycling chain- the glass recycling chain
becomes overloaded [17].
With this in mind, the
additional loading of automotive waste may place
considerable strain on our recycling system.
Alternatives should therefore be examined. In a recent
article, Oliver [18] said that "There is the possibility of
using waste glass as aggregate for road building, but
here there is the possibility of poaching the market from
other secondary materials". Therefore, another more
attractive alternative may lie in coastal defences.
Glass for Coastal Defence
From 1995-1999 a rebuild project was completed to
restructure the coast in Eastbourne, England. This
single project consumed 780,000 m3 of beach
replenishment, 54,000 tonnes of rock, 30,000 tonnes of
concrete and 20,000 tonnes of granite. Given that this
single project consumed so much material, it would
seem that there would be not too much of a problem in
consuming the whole communities 180,000 tonnes of
glass in coastal construction projects around the EU.
Here there would be no shifting of alternative secondary
material markets- and the whole concept could have
large environmental gain. Indeed, there is now concern
over the use of Scandinavian rock in construction and it
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is not seen as renewable. If a hilltop is removed for its
rock, the hilltop will not grow again…[19].
Glass is ideal for coastal projects for many reasons. It is
totally inert so it will not affect wildlife or contaminate the
water. It is thermally stable so it will not be prone to
cracking or any dimensional change associated with
ambient temperatures. And perhaps most importantly, it
can safely erode. It can absorb energy from the waves
as a coastal defence mechanism, and as it erodes, it
merely returns to the silica from whence it came- a
complete cycle.
remove. By incorporating active disassembly, not only
will it be possible to increase recycling percentages, but
it will also be possible to cut recycling time.
REFERENCES
[1] Directive 2000/53/EC of the European Parliament
and of the Council of 18 September 2000 on end-of life
vehicles, article 7
[2] Ian Gaskin, Environmental Director- Universal
Salvage Services
CONCLUSIONS AND FURTHER WORK
[3] Society of Motor Manufacturers and Traders (SMMT).
Active disassembly has already proved itself with
consumer electronics as being a realistic solution to a
recycling problem. In the harsh environment of a motor
vehicle, further work needs to be done. Firstly, to make
full use of shape memory polymers, higher transition
temperatures need to be developed commercially, as do
polymer constructions of differing durometers. Shape
memory polymers are a far more attractive prospect
than shape memory alloys, as they are much cheaper,
and they can be recycled with the PU seat foams
already contained within a vehicle.
http://www.smmt.co.uk/news/pressreleasedisplay.asp?ar
ticleid=74
Active disassembly can provide a quick and easy
disassembly method for automotive parts when the end
of life condition occurs. Disassembly by inserting a hot
probe into parts of the vehicle may be one way of
triggering the fastenings. Certainly the design of the
vehicle will have to be optimised somewhat to facilitate
this principle. While it is certainly possible that the
surface of an assembly may reach the required
triggering
temperature,
the
internal
assembly
temperature may be far lower. Provisions will have to be
made to facilitate the conduction or convection of heat
through an assembly to rapidly raise the temperature of
the appropriate heat critical part. There is also the
possibility of electrically triggering the release of some
parts by using thin SMA 'muscle wires' that get hotter
and shorten when they are heated by an electric current.
Again, this is another area that we need to fully
investigate to maximise the recycling potential of these
interesting materials
Implementation of active disassembly window
channels could be almost immediate, as the channels
can simply bolt or clip onto existing assemblies. They
can also aid vehicle repair, as the glass only can be
replaced. However, to maximise the benefits of active
disassembly the most likely areas of implementation will
be those areas where the cost saving to be made will be
highest. This means that after this preliminary study, the
next area to be tackled will be the highly complex
instrument panel (IP). The mix of materials in an IP is
high, as well as the individual component cost- mainly
due to the extensive use of sub-assemblies. Using what
we have learned from the car door assembly, we will try
to apply to an IP. Not only is the IP an expensive part of
the car, it is also one of the most time consuming to
[4] Prum, N.
Scrap Steel from ELV: A Valuable
Secondary Ore Material for the Steel and Zinc
Industries. In, Proceedings of the first International
Automobile Recycling Congress, Geneva, Switzerland.
ICM 2001.
[5] Directive 2000/53/EC of the European Parliament
and of the Council of 18 September 2000 on end-of life
vehicles, article 6 subsection 3(c)
[6] Oliver, J., Recycling World news-desk article.
Recycling World issue 342, June 1st 2001, pp.10
[7] Information courtesy of Jeremy Downing, Engineer
with Permabond Engineering adhesives
[8] Chiodo et al, Eco-Design for Active Disassembly
Using Smart Materials. In, Proceedings of the Second
International Conference on Shape Memory and
Superelastic Technologies, California, USA. Pp 269-274.
SMST 1997.
[9] Company Literature. Dynalloy, (shape memory alloy
producer). http://www.dyanalloy.com
[10] Gordon, R. F. Design Principles for Cu-Zn-Al
Actuators, in 'Engineering Aspects of Shape Memory
Alloys', Duerig, T. W., et al, ed. Butterworth-Heinmann,
New York 1990. Pp.245
[11] Tautzenberger, P., Thermal Actuators: A
Comparison of Shape Memory Alloys with Thermostatic
Bimetal and Wax Actuators, in 'Engineering Aspects of
Shape Memory Alloys', Duerig, T. W., et al, ed.
Butterworth-Heinmann, New York 1990, pp.208
[12] Chiodo, J., Billett, E. H., Harrison, D. J., Preliminary
Investigations of Active Disassembly Using Shape
Memory Polymers. In, Proceedings, EcoDesign '99:
First International Symposium on Environmentally
Conscious Design and Inverse Manufacture. Tokyo,
Japan. IEEE 1999. Pp. 590-593
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[13] Irie, M. Shape Memory Polymers. In, Shape
Memory Materials, Ed by Otsuka and Wayman. Pp 203207, Cambridge University Press 1998,
[14] Company Literature.
Cast Solutions
Winfield, Innovative Liquid
http://www.winfieldinds.com/typical_properties_polyurethane.htm
[15] Ford Engineering Material Specification, WSSM15P4-E. Pp.3-5
[16] Department of the Environment Transport and the
Regions, Waste Strategy- Report of the Market
Development Group.
http://www.environment.detr.gov.uk/waste/strategy/mdg/
report/4.htm
[17] Berryman, For a Brighter Future. Glass recycling
literature. Berryman Glass
[18] Oliver, J. Editorial comment, In Recycling World.
Issue 344, June 29th 2001, pp3
[19] Brian
Duvivier
Waters,
Consultant
Engineer,
Posford
CONTACT
Nicholas Jones.
ADSM, Brunel University, Department of Design
Coopers Hill Lane, Egham, Surrey, TW20 0JZ, England
Tel +44 (0) 1784-431341 ext. 202/239
Fax +44(0) 1784-432777
nick.jones@brunel.ac.uk
http://www.brunel.ac.uk/research/adsm