- Email: [email protected]
Process Requirements for Disassembly and Recycling
Copyright © IFAC Infonnation Control in Manufacturing, Nancy - Metz, France, 1998
PROCESS REQUIREMENTS FOR DISASSEMBLY AND RECYCLING M.H. Gentil, A. Castaing and J.P. Bourrieres LAP/GRAI, University Bordeaux 1 351, Cours de la Liberation, 33405 Talence cedex France Tel: (33) 05 56 84 65 30, Fax: (33) 05 56 84 66 44 E-mail: {name}@lap.u-bordeaux.fr
Abstract: Waste flow processing is become a major challenge of industrialized nations. In most of EU members countries, rough dumping will be legally forbidden by year 2002, so that the whole waste flow will be processed before dumping or recycled towards industry as raw materials. The legislative pressure aims at forcing manufacturers to be responsible for their products at their end of life. In the case of used products (industrial and domestic equipment), disassembly is a necessary step before any further processing towards dumping or recycling. This paper highlights some requirements for the industrialization of disassembly processes, a key problem being the need for two types of infonnation: off-line technical data on product and process data to be obtained from manufacturers, as well as on-line measures to let disassembly processes adapt to highly variable state of used products. Copyright © 1998 IFAC. Keywords : Environmental engineering, Product transformation, Recycling systems configuration, Process quality requirements, ISO norms.
1. INTRODUCTION
revaluation units specialized in specific -plastics, metals, rubber or glass- processing.
The protection of the environment is become a major challenge for all industrialized countries. According to an European agreement, member states have legislated to control waste dumping and to support recycling activities. By year 2002, dumping will be limited to ultimate waste, the whole flow of rough waste being processed to recycle energy through incineration or materials to be reused in new products.
This paper focuses on process requirements and quality issues in disassembly units. A structured view of what a product is first presented to be used as a referential for disassembly activities. Typical contexts of recycling are then examinated to be referred throughout the paper. Two key issues are finally addressed :
To be economically viable, recycled materials should be competitive with regard of quality and price, which requires to minimize both logistics and revaluation costs, and to eliminate processing faults as well. Automation is the unique response to mass processing and to market requirements in tenns of quality and cost.
•
the traceability of original technical data related to products and corresponding assembly processes,
•
the adaptativity of disassembly units to face with the varying physical state of end-of-life products.
2. PRODUCT MODELING
Moreover, the high diversity of products -in shape and in material- requires highly flexible units to sort and disassemble composed products before dispatching quasi-homogeneous materials towards
Seen from the marketing, a product provides a set of technical, aesthetic, social, etc.. functions to a client. These functions endows the product with value.
835
Engineering is the art of turning the functional definition of a product into a complete technical specification, in terms of: •
•
•
structures, i.e. assemblies and subassemblies matching technical subfunctions (for instance, the gear box in a car) or justified by assembly easiness. Some of the assembly links are reversible (screws), whereas other are not (welding, etc...) or require specific operations.
•
the salvage of components: chips from electronic cards, technical parts from an engine, etc..
•
more commonly, the salvage of materials contained in used products : aluminum and ferrous metals mainly.
Furthermore, an important flow of scrap is produced by manufacturing industries -with various added value on materials, parts or products -, which also has to be processed by recycling facilities.
components, i.e. parts separately manufactured, made of a single material, to be assembled.
Finally, recycling activities can be classified as combinations of :
materials, generally manufactured massively by dedicated industries.
According to this view (Fig. 1), engineering is a specification process which performs the virtual decomposition of the future product, whereas manufacturing makes the successive transformations leading from the materials to the final functions of the product. Note that quality issues in manufacturing also match this referential, the functional quality of the product being conditional on the quality of assembly (structures), of manufacturing (components) and of materials.
•
the value target, defining the objective of the activity. The value is recovered from the product and/or regenerated through revaluation.
•
the state of the product from which the value is to be extracted.
These combinations lead to different revaluation paths (Fig. 2) with specific re-processing.
:i ~S~~t~l ~ . .....:rtt1~
E n g
Functions Structures Components Materials
::::l:::..
. ....
.DisGS6emhly .
......... ,
·Assembly .
· . • . • . . . • • . . • • 'e;",,' .
i
n e e
· : ::
: : : : Mtip~in:ing: : : : : . : :
. 'Parr' . ~
r
· ... J .
n
g
:
Manufacturing
't'"
Part· . .
• .•.•.....
j.st.~.e~.·t. :. :i ; i1~rt:r:~
, .. Processing· . · . Material' . ~ . . .
Fig. 1. Product decomposition
Fig. 2. Product revaluation
3. PRODUCfREVALUATION
4. RECYCLING INDUSTRIES
The value of a product decreases when its main functions disappear, for different reasons linked to its own state (breakdown, loss of reliability), to the point of the user or to the evolution of the environment (obsolescence, fashion effects, etc..). A product turns to waste when its residual functions are insufficient to satisfy any owner, so that its commercial value is nil.
Recycling is a general concept which covers a large scope of activities. The enterprises can be classified according to two criteria : the process and the industrial context.
4.1 Process The enterprises involved in the recycling loop (Fig.3) are specialized in technological activities to perform a part of the whole recycling process, most of time split in concordance with the main product value levels identified above :
The commercial justification of recycling is the revaluation of waste, the value added brought by the transformation process being cumulated to the residual value of waste (if any). Recycling can then consist in : •
•
the salvage of structures : tyre remolding, copier cartridges, etc..
836
disassembly units provide sorted components from complex used products (cars, domestic machines, PCs, etc...)
•
component revaluation: part re-machining
The flexibility concept has to be refined as follows:
•
component shredding units (or any other destructive process leading to recover materials from components)
•
•
material revaluation units, to transform material scrap into basic materials for industry, through chemical, thermal, ... reprocessing.
upstream flexibility is the capacity of the unit to process variable inputs, both in nature (range of used products, components, materials to be processed) and in quality (limits to shape deformation, heterogeneity , cleanness...) of inputs. Note that supplies can be waste from manufacturing enterprises, for instance metallic scrap from mechanical industries, with a high level of homogeneity.
•
downstream flexibility (or customization) allows the enterprise to react to sale opportunities through a range of value-added outputs.
raw . ultimate enVIronment . Is matena ~ ~ waste 1st transformation incineration homogeneots revaluation material
\r
manufac ring
revaluation
component assembly product \ distribution
~V:eterogen:ous "'
l
matenal
schreddine
Such an industrial context brings a lot of problems : •
preparing homogeneous batches of used products is difficult, given the high variety of products and their dissemination. To plan and schedule the activity of a disassembly or revaluation unit requires advanced techniques ~for instance, group technology) to launch economical series.
•
to access the technical data relating to products is a key problem, since these infonnation are the property of the independent companies in which the used products have been originally designed and manufactured. In other words, product information has been lost between the manufacturing system and the recycling system. Note that a first step toward traceability has been made by the Directive 94/621CE of the European Parliament, which obliges to mark materials used in packaging (plastics, papers, metals, ...).
~component
disassembly / worn product collectine
"--use/ Fig. 3. Recycling activities (underlined) among industrial activities 4.2 Industrial context We here consider the relationships between the manufacturing system (providing products to final consumers) and the recycling system (processing used products). Three basic situations can be identified.
Cooperative recycling (type 2) : In another typical situation, both manufacturing and recycling systems belong to a single company, or are composed of explicitly collaborating companies. For some big companies (computer manufacturers, automotive industry), it is a strategic will to recover used products, for a question of image or confidentiality mainly. Then the recycling loop is included entirely in a single system (Fig. 5), which largely facilitates a rational approach to recycling :
Market environment (type I) : In a free competitive environment (Fig. 4), a recycling enterprise has to find outlets for its "products" and to search for suppliers as well, so that the enterprise is involved in upstream and downstream supplier-to-customer relationships like any enterprise from the competitive sector. Quality and price (through productivity) are here the main keys to competition.
•
product technical data are accessible
•
the range of used products to process is limited to the products previously manufactured in another unit of the same company
•
collecting logistics can take into account the management requirements of the disassembly or revaluation unit, and gather products consequently.
Moreover, collecting used products can be made through the distribution network itself, which considerably reduces the cost of recycling logistics.
Manufacturing sector Fig. 4. Market environment (type 1)
837
company integrated recycling system
Fig. 5. Cooperative recycling (type 2)
,~ • •
---: ...•
external ;', supply
, ... _".;,.
".'~.•_""',,"""'"
'.
.'"
,.' ',",',' •. 'J
passed
~~
.· .·. ',.....
the variability of the physical state of products and its incidence on quality management
•
the availability of original technical data on products and manufacturing processes (traceability).
•.•
........~·product
.....,.~~I
5.1 Product information and traceability One key-problem of disassembly is to have product technical data at disposal, i.e. the data that were initially necessary to build the product : product internal structure, assembly links and materials. If not obtained from the manufacturer, these indispensable information must be rebuilt through analysis on the disassembly plant.
Fig. 6. Internal recycling (type 3) Recycling here matches the management of quality in manufacturing. Non conform products are disassembled to retouch some components or assembly links. Otherwise, scrap is sold - if valuable - on the external recycling market. In the short tenn, recycled flows reveal a fault rate in manufacturing, with an incidence on production management and productivity. The continuous improvement of quality then aims to decrease the fault rate and recycled flows. Nevertheless, the necessity to disassemble non conform products or structures can justify some Design For Disassembly (DFD) (Kriwet, et al., 1995) efforts.
Depending of the industrial context of disassembly (see section 4.2), the technical communication between the manufacturer and the disassembler is more or less easy, given also the life duration of the product (years, most of time): Type 1 context (market) : the manufacturer and the disassembler are fully independent. This context makes any communication unlikely and requires high shape recognition and diagnosis capacities on the disassembly site, where old technology products must be totally re-discovered. Some experiments reported by Siemens (Ebach, 1997) demonstrate the feasibility of televisionsets disassembly without any technical database.
Finally, the key problems encountered are strongly dependent on the industrial context of recycling, as shown in Table 1, regarding :
Type 2 (cooperative) and type 3 (internal) context: the communication between both industrialists can be contractually assured, in the short term to facilitate disassembly process, and in a longer term to redesign products and let disassembly costs decrease.
Table 1 Comparison of recycling industrial contexts
type 1 (market) type 2 (cooperative) type 3 (internal)
•
Disassembly provides separate components from a more or less complex structure. Disassembly process requirements strongly depend on the final target which can be to recycle components as such or to recycle materials subsequently. Disassembly can functionally be seen as symmetrical to assembly. In fact, disassembly is rarely a reverse assembly process, which is highlighted by the following.
recycling within manufacturing unit '.
the variability of used product supply and its incidence on production management
5. DISASSEMBLY
Internal recycling (type 3) : A third typical context is recycling scrap on the manufacturing site itself (Fig.6).
~'.''''
•
supply variability high
state variability high
traceability
limited
high
high
low
low
total
null
838
technical data
com~ I ~ p~utt !ssemblY
stable input Quality
~
tl
product database process database
(s)
on-line inspection
stable output quality requirements
Process Quality control
Fig. 7a. Process quality requirements in assembly... not revaluable revaluable revaluable materials components on-line diagnosis
technical data
Fig. 8. Adaptive disassembly process components
or
produet(s)
The depth of the disassembly results from the diagnosis perfonned at the different steps of the process : reversibility of assembly links, shape of components, quality of materials (Fig. 8).
materials
variable input Quality S::J
variable output
\1 quality requirements
Process Quality control
5.3 Disassembly operations
Fig. 7b. ...vs disassembly
Many assembly operations (welding, crimping, etc...) are not reversible and require specific disassembly techniques and tools (Tuominen, 1997). Other assembly techniques (clipping) are reversible if specific tools are applied (Fig.9). Moreover, dismantling a product to recover materials does not require to preserve the integrity of its components. It is then often justified to use destructive operations (drilling, sawing, etc.. ) which significantly spare timecycle and costs.
5.2 On-line quality diagnosis and adaptive disassembly process
The quality disparity of assembly process inputs (components) is very low today thanks to certification. The situation is highly different for disassembly, since the inputs of the process are here used products whose physical state is uncertain. Disassembly processes have to be adaptive to face with the physical state variability of used products (Fig. 7a and 7b). Measures and diagnosis on each instance of product can be necessary to customize the process accordingly. The diagnosis should integer both economical and technical parameters such as : the current raw material quotation, the disassembly costs, product technical data, on-line inspection and measures. Both advanced sensoring techniques, especially vision systems (Schmidt, 1996), and human inspection can be necessary to assess the value of the product and the cost of the disassembly process.
disassembly tool
Fig. 9. Specific disassembly tool
839
The motions to separate parts most of time combine two phases: •
•
7. CONCLUSION The industrialization of disassembly seems to be ineluctable, whether to supply recycling or -more massively- to process used products with the view of dumping them as ultimate waste.
fine motions are first required to extract the parts under more or less strong mechanical constraints depending on the effective number of degrees of freedom (d.oJ.) of the task. During this phase, the motion control has to manage mechanical interactive efforts very similarly to assembly efforts.
Costs must be squeezed and process quality improved as well, which requires a total life-cycle approach to manufacturing, both on technical and logistical issues. BasicaHy, disassembly is far to be simply the reverse of assembly. The lack of traceability of initial manufacturing technical data is a key problem which justifies that manufacturers explicitly cooperate with recyclers, or, more realistically, that both belong to a single company. To us, the identification of disassembly process requirements is the starting point to the rationalization of disassembly and recycling activities. The major issues to be then addressed as a result are on one hand production management of disassembly plants (Seliger and Hentschel, 1994) and on the other hand design for disassembly (Kriwet, et al., 1995); Castaing, et al., (1997).
large motions are then necessary to take the dismounted components away and place them under various positioning constraints in a suitable container. When the goal is to recover components as such, the deposit motions (on a box, a pallet, etc..) are as much constrained as the feeding motions in an assembly task. When the goal is to recover materials, gravity is commonly used to collect the dismounted parts in a container, with a view to subsequent processing. 6. NORMALIZATION
6.1 Product normalization
REFERENCES Castaing A., P. Girard, J.P. Bourrieres (1997). In : Incidence of disassembly constraints on Complex product design. Proc. of ASI'97, July 14th-18th, Budapest. Ebach H. (1997). In : ADAS - Autonomous disassembly by advanced shape recognition. Proc. of the European Conference on Integration in Manufacturing, pp. 213-223, Dresden, 24-26 Sept. 1997. Kriwet A., E. Zussman, G. Seliger (1995). In : Systematic integration of design for recycling into product design. Int. journ. of Production Economics, vol. 38, pp 15-22, Elsevier, Amsterdam. Schmidt A. (1996). In : Neural network-based robots for the disassembly and recycling of automotive products. (ESPRIT III 8338 NEUROBOT). Proc. of the EURIAS-SPI Workshop in Bremen. Seliger G., C. Hentschel (1994). In : Disassembly process planning to support the recyclability of used technical products. Proc. of the vision EUREKA Conf. Industrial Opportunities in Waste Management, Lillehammer, Norway. Tuominen J. (1997). In : Automated car disassembly. Proc. of the European Conference on Integration in Manufacturing, pp. 195-211, Dresden, 24-26 Sept..
Today, product nonns mainly relate to product use and do not systematically integrate the disassemblability and the recyclability of products : in France, NF norms are dominant and deal only with longevity, safety, functional quality, reliability of products. The French norm "NF Environnement" includes precise exigencies on the recyclability of products, but does not address technical prerequisites for disassemblability.
6.2 Process normalization Since 1996, ISO 14000 norms are available for environmental management. This set of norms deal with the management of non intentional production (waste, pollution) : • ISO 14004 specifications for internal use • ISO 1400 1 for certification • IS014010, 11 and 12 for audits ISO 14000 -like ISO 9000- norms aim at checking the existence of means to apply a strategy in the company : strategic orientation, involvement of the management staff, deployment of objectives, internal audits, proactive and reactive procedures, reviews, etc... Note that IS09000 aims at satisfying the customer in a contractual framework, whereas ISO 14000's goal is the protection of the environment without strict contractual framework.
840
PROCESS REQUIREMENTS FOR DISASSEMBLY AND RECYCLING M.H. Gentil, A. Castaing and J.P. Bourrieres LAP/GRAI, University Bordeaux 1 351, Cours de la Liberation, 33405 Talence cedex France Tel: (33) 05 56 84 65 30, Fax: (33) 05 56 84 66 44 E-mail: {name}@lap.u-bordeaux.fr
Abstract: Waste flow processing is become a major challenge of industrialized nations. In most of EU members countries, rough dumping will be legally forbidden by year 2002, so that the whole waste flow will be processed before dumping or recycled towards industry as raw materials. The legislative pressure aims at forcing manufacturers to be responsible for their products at their end of life. In the case of used products (industrial and domestic equipment), disassembly is a necessary step before any further processing towards dumping or recycling. This paper highlights some requirements for the industrialization of disassembly processes, a key problem being the need for two types of infonnation: off-line technical data on product and process data to be obtained from manufacturers, as well as on-line measures to let disassembly processes adapt to highly variable state of used products. Copyright © 1998 IFAC. Keywords : Environmental engineering, Product transformation, Recycling systems configuration, Process quality requirements, ISO norms.
1. INTRODUCTION
revaluation units specialized in specific -plastics, metals, rubber or glass- processing.
The protection of the environment is become a major challenge for all industrialized countries. According to an European agreement, member states have legislated to control waste dumping and to support recycling activities. By year 2002, dumping will be limited to ultimate waste, the whole flow of rough waste being processed to recycle energy through incineration or materials to be reused in new products.
This paper focuses on process requirements and quality issues in disassembly units. A structured view of what a product is first presented to be used as a referential for disassembly activities. Typical contexts of recycling are then examinated to be referred throughout the paper. Two key issues are finally addressed :
To be economically viable, recycled materials should be competitive with regard of quality and price, which requires to minimize both logistics and revaluation costs, and to eliminate processing faults as well. Automation is the unique response to mass processing and to market requirements in tenns of quality and cost.
•
the traceability of original technical data related to products and corresponding assembly processes,
•
the adaptativity of disassembly units to face with the varying physical state of end-of-life products.
2. PRODUCT MODELING
Moreover, the high diversity of products -in shape and in material- requires highly flexible units to sort and disassemble composed products before dispatching quasi-homogeneous materials towards
Seen from the marketing, a product provides a set of technical, aesthetic, social, etc.. functions to a client. These functions endows the product with value.
835
Engineering is the art of turning the functional definition of a product into a complete technical specification, in terms of: •
•
•
structures, i.e. assemblies and subassemblies matching technical subfunctions (for instance, the gear box in a car) or justified by assembly easiness. Some of the assembly links are reversible (screws), whereas other are not (welding, etc...) or require specific operations.
•
the salvage of components: chips from electronic cards, technical parts from an engine, etc..
•
more commonly, the salvage of materials contained in used products : aluminum and ferrous metals mainly.
Furthermore, an important flow of scrap is produced by manufacturing industries -with various added value on materials, parts or products -, which also has to be processed by recycling facilities.
components, i.e. parts separately manufactured, made of a single material, to be assembled.
Finally, recycling activities can be classified as combinations of :
materials, generally manufactured massively by dedicated industries.
According to this view (Fig. 1), engineering is a specification process which performs the virtual decomposition of the future product, whereas manufacturing makes the successive transformations leading from the materials to the final functions of the product. Note that quality issues in manufacturing also match this referential, the functional quality of the product being conditional on the quality of assembly (structures), of manufacturing (components) and of materials.
•
the value target, defining the objective of the activity. The value is recovered from the product and/or regenerated through revaluation.
•
the state of the product from which the value is to be extracted.
These combinations lead to different revaluation paths (Fig. 2) with specific re-processing.
:i ~S~~t~l ~ . .....:rtt1~
E n g
Functions Structures Components Materials
::::l:::..
. ....
.DisGS6emhly .
......... ,
·Assembly .
· . • . • . . . • • . . • • 'e;",,' .
i
n e e
· : ::
: : : : Mtip~in:ing: : : : : . : :
. 'Parr' . ~
r
· ... J .
n
g
:
Manufacturing
't'"
Part· . .
• .•.•.....
j.st.~.e~.·t. :. :i ; i1~rt:r:~
, .. Processing· . · . Material' . ~ . . .
Fig. 1. Product decomposition
Fig. 2. Product revaluation
3. PRODUCfREVALUATION
4. RECYCLING INDUSTRIES
The value of a product decreases when its main functions disappear, for different reasons linked to its own state (breakdown, loss of reliability), to the point of the user or to the evolution of the environment (obsolescence, fashion effects, etc..). A product turns to waste when its residual functions are insufficient to satisfy any owner, so that its commercial value is nil.
Recycling is a general concept which covers a large scope of activities. The enterprises can be classified according to two criteria : the process and the industrial context.
4.1 Process The enterprises involved in the recycling loop (Fig.3) are specialized in technological activities to perform a part of the whole recycling process, most of time split in concordance with the main product value levels identified above :
The commercial justification of recycling is the revaluation of waste, the value added brought by the transformation process being cumulated to the residual value of waste (if any). Recycling can then consist in : •
•
the salvage of structures : tyre remolding, copier cartridges, etc..
836
disassembly units provide sorted components from complex used products (cars, domestic machines, PCs, etc...)
•
component revaluation: part re-machining
The flexibility concept has to be refined as follows:
•
component shredding units (or any other destructive process leading to recover materials from components)
•
•
material revaluation units, to transform material scrap into basic materials for industry, through chemical, thermal, ... reprocessing.
upstream flexibility is the capacity of the unit to process variable inputs, both in nature (range of used products, components, materials to be processed) and in quality (limits to shape deformation, heterogeneity , cleanness...) of inputs. Note that supplies can be waste from manufacturing enterprises, for instance metallic scrap from mechanical industries, with a high level of homogeneity.
•
downstream flexibility (or customization) allows the enterprise to react to sale opportunities through a range of value-added outputs.
raw . ultimate enVIronment . Is matena ~ ~ waste 1st transformation incineration homogeneots revaluation material
\r
manufac ring
revaluation
component assembly product \ distribution
~V:eterogen:ous "'
l
matenal
schreddine
Such an industrial context brings a lot of problems : •
preparing homogeneous batches of used products is difficult, given the high variety of products and their dissemination. To plan and schedule the activity of a disassembly or revaluation unit requires advanced techniques ~for instance, group technology) to launch economical series.
•
to access the technical data relating to products is a key problem, since these infonnation are the property of the independent companies in which the used products have been originally designed and manufactured. In other words, product information has been lost between the manufacturing system and the recycling system. Note that a first step toward traceability has been made by the Directive 94/621CE of the European Parliament, which obliges to mark materials used in packaging (plastics, papers, metals, ...).
~component
disassembly / worn product collectine
"--use/ Fig. 3. Recycling activities (underlined) among industrial activities 4.2 Industrial context We here consider the relationships between the manufacturing system (providing products to final consumers) and the recycling system (processing used products). Three basic situations can be identified.
Cooperative recycling (type 2) : In another typical situation, both manufacturing and recycling systems belong to a single company, or are composed of explicitly collaborating companies. For some big companies (computer manufacturers, automotive industry), it is a strategic will to recover used products, for a question of image or confidentiality mainly. Then the recycling loop is included entirely in a single system (Fig. 5), which largely facilitates a rational approach to recycling :
Market environment (type I) : In a free competitive environment (Fig. 4), a recycling enterprise has to find outlets for its "products" and to search for suppliers as well, so that the enterprise is involved in upstream and downstream supplier-to-customer relationships like any enterprise from the competitive sector. Quality and price (through productivity) are here the main keys to competition.
•
product technical data are accessible
•
the range of used products to process is limited to the products previously manufactured in another unit of the same company
•
collecting logistics can take into account the management requirements of the disassembly or revaluation unit, and gather products consequently.
Moreover, collecting used products can be made through the distribution network itself, which considerably reduces the cost of recycling logistics.
Manufacturing sector Fig. 4. Market environment (type 1)
837
company integrated recycling system
Fig. 5. Cooperative recycling (type 2)
,~ • •
---: ...•
external ;', supply
, ... _".;,.
".'~.•_""',,"""'"
'.
.'"
,.' ',",',' •. 'J
passed
~~
.· .·. ',.....
the variability of the physical state of products and its incidence on quality management
•
the availability of original technical data on products and manufacturing processes (traceability).
•.•
........~·product
.....,.~~I
5.1 Product information and traceability One key-problem of disassembly is to have product technical data at disposal, i.e. the data that were initially necessary to build the product : product internal structure, assembly links and materials. If not obtained from the manufacturer, these indispensable information must be rebuilt through analysis on the disassembly plant.
Fig. 6. Internal recycling (type 3) Recycling here matches the management of quality in manufacturing. Non conform products are disassembled to retouch some components or assembly links. Otherwise, scrap is sold - if valuable - on the external recycling market. In the short tenn, recycled flows reveal a fault rate in manufacturing, with an incidence on production management and productivity. The continuous improvement of quality then aims to decrease the fault rate and recycled flows. Nevertheless, the necessity to disassemble non conform products or structures can justify some Design For Disassembly (DFD) (Kriwet, et al., 1995) efforts.
Depending of the industrial context of disassembly (see section 4.2), the technical communication between the manufacturer and the disassembler is more or less easy, given also the life duration of the product (years, most of time): Type 1 context (market) : the manufacturer and the disassembler are fully independent. This context makes any communication unlikely and requires high shape recognition and diagnosis capacities on the disassembly site, where old technology products must be totally re-discovered. Some experiments reported by Siemens (Ebach, 1997) demonstrate the feasibility of televisionsets disassembly without any technical database.
Finally, the key problems encountered are strongly dependent on the industrial context of recycling, as shown in Table 1, regarding :
Type 2 (cooperative) and type 3 (internal) context: the communication between both industrialists can be contractually assured, in the short term to facilitate disassembly process, and in a longer term to redesign products and let disassembly costs decrease.
Table 1 Comparison of recycling industrial contexts
type 1 (market) type 2 (cooperative) type 3 (internal)
•
Disassembly provides separate components from a more or less complex structure. Disassembly process requirements strongly depend on the final target which can be to recycle components as such or to recycle materials subsequently. Disassembly can functionally be seen as symmetrical to assembly. In fact, disassembly is rarely a reverse assembly process, which is highlighted by the following.
recycling within manufacturing unit '.
the variability of used product supply and its incidence on production management
5. DISASSEMBLY
Internal recycling (type 3) : A third typical context is recycling scrap on the manufacturing site itself (Fig.6).
~'.''''
•
supply variability high
state variability high
traceability
limited
high
high
low
low
total
null
838
technical data
com~ I ~ p~utt !ssemblY
stable input Quality
~
tl
product database process database
(s)
on-line inspection
stable output quality requirements
Process Quality control
Fig. 7a. Process quality requirements in assembly... not revaluable revaluable revaluable materials components on-line diagnosis
technical data
Fig. 8. Adaptive disassembly process components
or
produet(s)
The depth of the disassembly results from the diagnosis perfonned at the different steps of the process : reversibility of assembly links, shape of components, quality of materials (Fig. 8).
materials
variable input Quality S::J
variable output
\1 quality requirements
Process Quality control
5.3 Disassembly operations
Fig. 7b. ...vs disassembly
Many assembly operations (welding, crimping, etc...) are not reversible and require specific disassembly techniques and tools (Tuominen, 1997). Other assembly techniques (clipping) are reversible if specific tools are applied (Fig.9). Moreover, dismantling a product to recover materials does not require to preserve the integrity of its components. It is then often justified to use destructive operations (drilling, sawing, etc.. ) which significantly spare timecycle and costs.
5.2 On-line quality diagnosis and adaptive disassembly process
The quality disparity of assembly process inputs (components) is very low today thanks to certification. The situation is highly different for disassembly, since the inputs of the process are here used products whose physical state is uncertain. Disassembly processes have to be adaptive to face with the physical state variability of used products (Fig. 7a and 7b). Measures and diagnosis on each instance of product can be necessary to customize the process accordingly. The diagnosis should integer both economical and technical parameters such as : the current raw material quotation, the disassembly costs, product technical data, on-line inspection and measures. Both advanced sensoring techniques, especially vision systems (Schmidt, 1996), and human inspection can be necessary to assess the value of the product and the cost of the disassembly process.
disassembly tool
Fig. 9. Specific disassembly tool
839
The motions to separate parts most of time combine two phases: •
•
7. CONCLUSION The industrialization of disassembly seems to be ineluctable, whether to supply recycling or -more massively- to process used products with the view of dumping them as ultimate waste.
fine motions are first required to extract the parts under more or less strong mechanical constraints depending on the effective number of degrees of freedom (d.oJ.) of the task. During this phase, the motion control has to manage mechanical interactive efforts very similarly to assembly efforts.
Costs must be squeezed and process quality improved as well, which requires a total life-cycle approach to manufacturing, both on technical and logistical issues. BasicaHy, disassembly is far to be simply the reverse of assembly. The lack of traceability of initial manufacturing technical data is a key problem which justifies that manufacturers explicitly cooperate with recyclers, or, more realistically, that both belong to a single company. To us, the identification of disassembly process requirements is the starting point to the rationalization of disassembly and recycling activities. The major issues to be then addressed as a result are on one hand production management of disassembly plants (Seliger and Hentschel, 1994) and on the other hand design for disassembly (Kriwet, et al., 1995); Castaing, et al., (1997).
large motions are then necessary to take the dismounted components away and place them under various positioning constraints in a suitable container. When the goal is to recover components as such, the deposit motions (on a box, a pallet, etc..) are as much constrained as the feeding motions in an assembly task. When the goal is to recover materials, gravity is commonly used to collect the dismounted parts in a container, with a view to subsequent processing. 6. NORMALIZATION
6.1 Product normalization
REFERENCES Castaing A., P. Girard, J.P. Bourrieres (1997). In : Incidence of disassembly constraints on Complex product design. Proc. of ASI'97, July 14th-18th, Budapest. Ebach H. (1997). In : ADAS - Autonomous disassembly by advanced shape recognition. Proc. of the European Conference on Integration in Manufacturing, pp. 213-223, Dresden, 24-26 Sept. 1997. Kriwet A., E. Zussman, G. Seliger (1995). In : Systematic integration of design for recycling into product design. Int. journ. of Production Economics, vol. 38, pp 15-22, Elsevier, Amsterdam. Schmidt A. (1996). In : Neural network-based robots for the disassembly and recycling of automotive products. (ESPRIT III 8338 NEUROBOT). Proc. of the EURIAS-SPI Workshop in Bremen. Seliger G., C. Hentschel (1994). In : Disassembly process planning to support the recyclability of used technical products. Proc. of the vision EUREKA Conf. Industrial Opportunities in Waste Management, Lillehammer, Norway. Tuominen J. (1997). In : Automated car disassembly. Proc. of the European Conference on Integration in Manufacturing, pp. 195-211, Dresden, 24-26 Sept..
Today, product nonns mainly relate to product use and do not systematically integrate the disassemblability and the recyclability of products : in France, NF norms are dominant and deal only with longevity, safety, functional quality, reliability of products. The French norm "NF Environnement" includes precise exigencies on the recyclability of products, but does not address technical prerequisites for disassemblability.
6.2 Process normalization Since 1996, ISO 14000 norms are available for environmental management. This set of norms deal with the management of non intentional production (waste, pollution) : • ISO 14004 specifications for internal use • ISO 1400 1 for certification • IS014010, 11 and 12 for audits ISO 14000 -like ISO 9000- norms aim at checking the existence of means to apply a strategy in the company : strategic orientation, involvement of the management staff, deployment of objectives, internal audits, proactive and reactive procedures, reviews, etc... Note that IS09000 aims at satisfying the customer in a contractual framework, whereas ISO 14000's goal is the protection of the environment without strict contractual framework.
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