Marzio Sorlini
email: marzio.sorlini@supsi.ch

Alessandro Fontana
email: alessandro.fontana@supsi.ch

Marino Alge
email: marino.alge@supsi.ch

Luca Diviani
email: luca.diviani@supsi.ch

Luca Canetta
email: luca.canetta@supsi.ch

Ingo Specht
email: i.specht@interroll.com

Sustainability Assessment and Advisory in Mould&Die: Implementation Challenges and Solutions

Keywords: Sustainability assessment, mould and die, injection moulding

The paper describes a possible but concrete implementation pattern that is currently used to introduce and apply a sustainability-centered strategy in a mould&die company (INTERROLL SA). Focus of the analysis, implementation requirements, designed procedures and a draft software architecture are here outlined, forming the conceptual basis for a value-adding and easily adoptable approach intended to promote the implementation of a so widelyspeculated strategic theory. The described path could be easily adapted to other mould&die companies and further extended to different industrial sectors.

Introduction

Most innovative manufacturing companies are today exploring sustainability-related strategies as a guide to re-design their business processes, either motivated by end customers' increased pressure towards environmentally-and socially-compliant products and processes [START_REF] Jounga | Categorization of indicators for sustainable manufacturing[END_REF] or, less virtuously, interested in catching the latest marketing wave. In both cases, such prospective adopters are looking for actual implementation examples and practical procedures to follow in order to become "sustainable" or "more sustainable" (than before or than the competitors). Unfortunately, a formalized approach supporting sustainability strategy implementation is still missing (some examples are available but focusing on mere environmental parameters or with limited applicability [START_REF]OECD Sustainable manufacturing toolkit: seven steps to environmental excellence[END_REF]): which are the steps a potential sustainable entrepreneur has to follow? Which are the available tools he can adopt? Which product/company lifecycle phases are more appropriate for starting such a path? A practical, experimented and industrial-oriented sustainability implementation procedure has been never described in literature (apart from [START_REF] Boër | Mass customization and sustainability. An assessment framework and industrial implementation[END_REF], where authors propose an exercise addressing a wooden furniture): lack of descriptive capabilities or lack of actual examples? According to literature [START_REF] Schaltegger | Managing the Business Case of Sustainability[END_REF][START_REF] Wüstenhagen | Business models for sustainable energy[END_REF], one of the major problems with sustainabilitycentred business models relates to the simultaneous pursuit of private (companies' and customers') and public (society and environment) benefits. As long as public benefits don't result into countable private advantages, more sustainable production systems and products may be competitively disadvantaged. From here it comes the first pre-requisite for sustainability strategies implementation: the availability of metrics. Metrics enable the measurement of sustainability and, specifically, of private (and, incidentally, public) benefits. Measuring allows comparison, thus enables decision-making. Many international initiatives have developed indicator sets, formulae and recommendations for this purpose, even if rarely addressing specific requirements of manufacturing environments. Authors coordinated and successfully completed an FP7 research project1 addressing this specific purpose: now a set of manufacturingfocused metrics has been consolidated and validated in real production contexts [START_REF] Bettoni | Sustainable Mass Customization Assessment[END_REF].

Being metrics an (almost) achieved pre-requisite, target identification is the second required step. The selection of a proper business case is fundamental to provide a value-adding, extensible and comprehensive analysis for future adopters. Manufacturing environments more likely adopting sustainability-enhancing practices are those where private and public benefits are (both) virtually significant. This happens in industries: (i) with a relevant impact on at least one of the sustainability spheres, (ii) with large room for improvements, (iii) witnessing relevant pressure from important stakeholders on sustainability-related themes, (iv) facing cost-based competition from low environmentally-and socially-sensitive countries.

Injection moulding is the most important commercial method of plastics processing. It is used to mass-produce components fast and with little or no finishing operations. Nearly all markets use injection moulded plastics (from packaging to building). The interaction with final customers is thus continuous and, sooner rather than later, there will be standards for carbon footprints or social friendliness in injection-moulded products manufacturing (point (iii)).

AMI [6] estimates that there are approximately 16,500 injection-moulding sites in West and Central Europe operating over 220,000 machines. This makes mould&die numerically relevant. The environmental profile of injection moulding has demonstrated its great impact: the overall injection moulding energy consumption in the U.S. in a yearly basis amounts to 2.06 x 10 8 GJ [START_REF] Thiriez | An environmental analysis of injection molding, Electronics and the Environment[END_REF], similar to the energy consumption of some developed countries (see points (i) and (ii) above).

In a 2010 report entitled The Future of the European Injection Moulding Industry, AMI observes that the European injection moulding industry faces weakness in demand across a range of end use sectors, with customers looking to reduce the price of components, while raw material and energy costs rise. This favours producers willing and able to relocate to lower-cost manufacturing sites out of Europe. As a result, the number of moulders operating in Europe have fallen by 9% over the past six years. European injection moulders are asked to identify a radically different competitive framework, and sustainability-focussed strategies are a really attractive chance to proactively reposition their business and capitalize on the environmental gaps of their operations, also considering the available options of performances improvements enabled by appropriate mould design [START_REF] Gantar | Resource Efficient Injection Moulding with Low Environmental Impacts[END_REF], careful material selection [START_REF] Recchioni | LCA as eco-design tool to support the development of injection moulded products[END_REF] or adopted manufacturing technology.

Exploiting preliminary results of the Swiss research project SAM (see § 6), promoted by SUPSI and INTERROLL SA, in this paper, authors are not meant to present and revise the state of the art of sustainability evaluation, but would like to describe their current experience in implementing sustainability assessment and advisory in a mould&die company. Preliminary decisions concerning the target of the analysis are discussed in § 2, while § 3 presents the specific requirements for sustainability adoption in the mould&die context. The designed solutions are conceptually presented in § 4, where the SAM platform architecture is formally described. Considerations on the achieved results and planned next steps are finally presented in § 5.

The Focus of the Sustainability Assessment

In conformity with the methodology of Life Cycle Assessment (LCA) [START_REF] Guinée | Life cycle assessment: past, present, and future Environmental science & technology[END_REF], the focus of the analysis has to be identified before a sustainability assessment is performed.

In mould&die industry, both the mould and the moulded product can be considered as the subject of the sustainability assessment, depending on the focus companies are more interested in. Within this industrial sector, companies activities and products are highly diversified ranging from (i) companies that directly design and produce the moulds and (sometimes) sell the moulded product as components for other final products, to (ii) enterprises that directly produce and commercialize the moulded plastic parts as final product, so moulds are not necessarily designed and realized by the company itself. The first group of companies seems to be more focused on the mould sustainability analysis, whereas the second group is more interested in calculating the sustainability level of the moulded products. In this perspective INTERROLL could be classified into the first group, but in order to confirm the common sense suggestion, the INTERROLL mould and moulded product lifecycles have been analysed.

The INTERROLL Mould and the Moulded Product Lifecycles

Lifecycle perspective is considered a must in the evaluation of the environmental, economic and social performances of a product [START_REF] Bettoni | Sustainable Mass Customization Assessment[END_REF]. Considering the mould and moulded product lifecycle, the following steps can be described. The Extraction takes into account the extraction of metal ore for the mould production, while the extraction of petrol for moulded part realization. Material processing considers the millwork of mould metals components and the transformation of the polymer in granules for the moulded product. In Part manufacturing metal milling is considered in mould production, while injection moulding for moulded parts. In Assembly the junction of mould components (e.g. plates) are considered for the mould. Starting form Assembly, the lifecycle of the moulded product is intimately related to those of the final product the plastic component belongs to. In the case of INTERROLL, Assembly includes the insertion of the plastic parts within the conveyor roller. The Use phase of the mould, injection moulding, corresponds to the manufacturing of the moulded product. Whereas, the use phase of moulded products coincide to the conveyor roller functioning. Mould Maintenance includes the substitution of some mould parts. In the case of the moulded part, Maintenance has to be evaluated within the conveyor roller repairing. The End of life of the mould is well known by INTERROLL, while it has many uncertainties for the moulded product since the conveyor roller could face different end of life scenarios in different countries. Eventually, the Transportation phase concerns the transportation of the mould components and the distribution of the moulded products. The description of the mould and the moulded product lifecycles of INTERROLL ease the definition of the focus of the sustainability assessment.

Analysis Focus

The lifecycles description allows to identify all the lifecycle activities directly managed by INTERROLL and that are affected by the decision taken by the company. Focusing on the mould, all the processes performed during lifecycle are either carried out or influenced by INTERROLL and decisions performed in mould design directly affect the sustainability performances of the mould. Extraction and material processing are influenced by mould design since the materials constituting the mould are here selected. Manufacturing and assembly processes are the results of design decisions. The use of the mould is the injection process, so it is the meeting point between the mould and the moulded product. In this phase, some elements as the energy consumed or the plastic wasted are actually affected by mould design; others are related to moulded product design as the quantity of the material injected. Eventually, also maintenance, End of Life and transportations are directly influenced by decisions performed during the supply chain configuration.

Analysing the moulded product lifecycle, it is possible to note that INTERROLL design decisions address the extraction, the material processing, the manufacturing phase and the upstream transportation. On the contrary, the company has a scarce control on the assembly, use, maintenance, end of life and downstream transportation phases since the moulded product is a part of a more complex product, i.e. the roller conveyor. In this perspective, choosing the mould as the focus of the sustainability analysis, INTERROLL is able to directly influence the environmental, economic and social impacts of the mould. Moreover, this approach allows to model and include into the analysis the impacts of the moulded product.

The Mould&Die Requirements in Sustainability Assessment

As mentioned in § 1, marketing and labelling is neither the only, nor the main goal of SAM, since the conceptualized tool/procedure is meant to promote awareness creation of both designers and managers, and guide them towards a more sustainable way to handle their products. In this chapter, requirements gathered and worked out in the preliminary steps of the project are presented and discussed.

What's the object to assess?

As discussed in § 2, the mould is the focus of the sustainability assessment, both targeting already existing and new moulds that have to be designed.

Which are the assessment dimensions?

The sustainability assessment has to be performed through the calculation of appropriate indicators. The process of identifying and selecting these indicators constitute a background for this work [START_REF] Bettoni | Sustainable Mass Customization Assessment[END_REF]. The use of numbers enables assessors to objectively evaluate the sustainability level of mould allowing to determine a benchmark and compare alternatives. Moreover, the chosen assessing dimensions have to be holistic from three complementary points of view, considering: (i) all the three sustainability areas (environment, economy and society); (ii) the product, the process and the supply chain; (iii) the lifecycle approach. This entails the need to get information of phases carried out by other actors and integrating them into a unique system.

Which are the needed data?

Data required for sustainability assessment can be grouped into three sets: (i) product-specific data, that need to be filled from time to time by the designer or the technician. These are morphological, technical and operational data strictly related to the given product and production process; (ii) company-specific data, related to the company and to its supply chain, and that can be updated on a longer time basis (e.g. when a new supplier joins the supply chain); (iii) general-knowledge data, usually coming from third-party databases (e.g.: Ecoinvent -www.ecoinvent.ch).

Who's the assessor? When are they performing the assessment?

Assessors are all the decision makers having some sort of power over the sustainability performances of the assessed object. Here two are the most relevant users: technical profiles (i.e.: mould designers) and managerial profiles. The first group is usually well alphabetized on the use of design software, but has no expertise on sustainability issues. Managerial profiles are usually not keen to handle shop-floor data and complex design software: they need a high-level management platform enabling comparison and storage of data intended for tactical to strategic decision support.

Two requirements are connected with the "timing". According to [START_REF] Canetta | Sustainable Product-Process-Network[END_REF], assessors are expected to act both ex-ante, during the design phase and ex-post, for pure assessment purposes. The analysed object is respectively the design of future moulds or existing moulds. The sustainability level of new moulds has to be measured in real time during the design phase in order to drive designers' choices. The sustainability level of already used moulds have to be measured for benchmarking and product labelling.

What's the envisaged response?

In general it is not possible to define "the sustainable product", but a "more sustainable product" compared to a benchmark. The array of indicators values concerning different mould configurations calculated by the platform is a valuable information for designers that are thus aware of the design decision effects on sustainability impact, and are driven in identifying an improvement path. The platform has to enable decision makers to identify a benchmark or select product concepts already assessed. In this perspective, this diagnostic feature would enable an iterative design path aiming to enhance the mould sustainability performances while designing. Finally, the analysis of sustainability impacts has to be carried out at different levels of detail. The final values of indicators provide an aggregate picture of how well the designed mould performs. This could be analysed through the above-mentioned comparison between two or more product configurations or "zooming" on a single indicator value or to given steps of the lifecycle or of the solution space.

The Solution Concept

In order to properly satisfy the requirements for the sustainability assessment of a mould, and considering the focus of the evaluation, a possible solution to implement the analysis of the environmental, economic and social performances is here drafted.

This solution is thought to be implemented via a software tool since a huge amount of data has to be gathered and managed and many calculations are required. In this perspective the design of the solution is presented through the Component diagram depicted in Fig. 1 obtained using the UML 2.0 notation. Two main macro-blocks could be identified, such as the front-end block and the back-end block.

The front-end block handles the interaction with the user and it is practically constituted by the Company Editor, the Mould Editor and the Diagnosis tool. The Company Editor encapsulates all GUI and logics that interact with the company-level data representation. Therefore, it's used to edit the information characterizing the company and its suppliers (e.g. the number of injuries, the sales turnover…), information that are needed for the sustainability assessment but that have not to be edited or added for each new SAM project. The Mould Editor contains GUI and logics used for the description of the mould in analysis. The Mould Editor component is indeed supported by the Diagrams Module that provides tree diagrams edit functionalities used for bill of material representation. It provides a specific live data model representing tree diagrams and their editing modelling, and undo/redo functionalities implemented as memento pattern. It also delivers graphical representation of the editing process. Answering to the management requirements, the Diagnosis Tool encloses GUI and mechanics used for browsing, analyse and compare sustainability assessment of various moulds and mould families.

The back-end block is meant to expose a series of services that are crucial for the calculation of the indicators values such as the Core, the Engine Block and the Importer. The Core module is thought to be the repository of the main live data model of the SAM platform and is responsible for its management, ensuring the continuous consistency of data. It also provides listening capabilities for other modules, enabling them to have a targeted reaction to every update of the model state. Moreover the core module provides generic GUI functionality to directly interact with the underlying data representation. The Engine Block is indeed constituted by the Assessment Service, the Simulation Service and the Maintenance Classifier. The Assessment Service module enables the sustainability assessment impacts computation. It will rely on specific live data model and a computational engine that is meant to calculate a defined set of sustainability indicators. The Simulation Service and the Maintenance Classifier modules have an important role for the indicators calculation performed during the design phase of the mould since they are meant to provide designer with forecasted data concerning the use and the maintenance phases. The Simulation Service provides simulation capabilities in order to predict energy consumption and other critical parameters for the detailed characterization of the injection moulding process. The Maintenance Classifier provides expert system functionalities to predict the required maintenance effort for different moulds. The Importer module contains data import functionalities that are registered in the application in order to allow the user to import various types of external data to facilitate the data entry process. This component thus represents the connection with the IT system already existing in INTERROLL (e.g. CAD, ERP…). The sustainability assessment in fact requires a certain variety of data concerning the product, the manufacturing system and the supply chain [START_REF] Canetta | Sustainable Product-Process-Network[END_REF] thus many data sources are needed.

Conclusions

Preliminary results achieved in implementing sustainability assessment and advisory in a mould&die company are here presented with the goal to provide prospective sustainability-conscious entrepreneurs with a practical path to follow when moving their business towards a more sustainable profile. Achieved results contemplate the focus of the sustainability analysis definition, requirements gathering and identification of a possible solution that could be easily translated into software platform conceptual architecture. Further steps are mandatory (and planned) addressing the final development and validation of the software platform, data collection and sustainability benefits measurement of the project, for both private and public audience. Since most of the requirements identified in § 3 have a general-purpose attitude, the ap-proach and the solution here outlined could be easily adapted to other mould&die companies and further extended to different industrial sectors.

Fig. 1 .

 1 Fig. 1. Component diagram of the solution concept

FoF.NMP.2010-2 -Sustainable Mass Customization, Mass Customization for Sustainability

Acknowledgements

This work has been partly funded by the Swiss Federal Commission for Technology and Innovation (CTI), through SAM -Sustainability Assessment in Mould and die (project number: 13522.1 PFES-ES). The authors wish to acknowledge the CTI for its support and INTERROLL SA for its contribution during the development of various ideas and concepts presented in this work.


Franco Paolo Pedrazzoli

Franco Antonio Cavadini
email: franco.cavadini@synesis-consortium.eu

Donatella Corti
email: donatella.corti@supsi.ch

Andrea Barni

Tommaso Luvini

An Innovative Production Paradigm to Offer Customized and Sustainable Wood Furniture Solutions Exploiting the Mini-Factory Concept

Keywords: furniture sector, mini-factory, short supply chain, green label, customization

des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

1

Production system innovation in the furniture sector

Europe is a major player in furniture on a global scale, with a total of more than 151.000 companies of which 95% are SMEs. Despite increasingly fierce global competition and significant relocation of manufacturing to low-wage countries, furniture continues to represent one of Europe's major industrial sectors with an annual turnover of more than 130 Billion Euro, and a total workforce of 1,4 million. Manufacturers in this sectors have 1) to become more agile and flexible, in response to the fast rate in which market trends change, demanding manufacturing infrastructures that can produce higher variations in smaller quantities and 2) to introduce personalized products and services whose added value can trigger market acceptance. In this framework, environment intangibles (such as environmental pollution, waste and energy consumption) are also recognized as urgent and the furniture sector faces the chal-lenge to actively consider and control those factors as well. This is because both customers demand sustainable products and governments are willing to sharpen regulations to commit companies to improve.

An innovative production paradigm aimed at supporting the European Industry to adapt to global competitive pressures is being developed by the European-funded project CTC. Within this the three-year project started in 2013, methods and innovative enabling technologies are developed and integrated to enable a local flexible manufacturing of green personalized products close to the customer in terms of features offered, place of fabrication, time to deliver, and cost. The integration of sustainability and customization issues is a promising strategy as stressed in recent works (e.g. [START_REF] Boër | Mass Customization and Sustainability. An assessment framework and industrial implementation[END_REF]). This vision is implemented and demonstrated within a European industrial sector of excellence: the furniture sector. The ultimate implementation envisions a "green factory behind a glass pane" directly in the shopping mall, where the customer witnesses the manufacturing of its personalized furniture.

In this paper the foreseen system and its impacts are described. First, the pillars the new production paradigm will be based on are introduced highlighting how they go beyond existing solutions. Then, an overview of the foreseen mini-factory layout and functioning is described before presenting the actors who will interact with it. Expected impacts of the proposed concept are discussed before drawing conclusions.

2

The production paradigm's pillars

Main pillars shaping the new production paradigm and their corresponding innovativeness are summarized in the following points: Formalized Design Approach (and related software technologies) to empower "design to manufacturing in one step" (which also includes the design finalization carried out by the customer himself). The development of a formalized furniture design approach refers to the tools and engineering methods to make the design seamlessly compatible with the manufacturing phase (fostering a design approach standardization), and must not be mistaken for the imposition of a common design style: distinctiveness of styles must be preserved as a key added value. CTC tools are meant to approach product design from a holistic perspective, integrating design methodologies in plug in software for currently available technologies in the woodworking sector. The integration of 3DCE and DfX methodologies promoted by CTC in current software tools and the reduction of complexity in the transition from CAD to CAM will foster a simplified approach to product definition according with an efficient product manufacturing. Starting from the analysis of the state-of-the-art in design methodologies ( [START_REF] Herrmann | New directions in design for manufacturing[END_REF]; [START_REF] Ellram | Product-process-supply chain: an integrative approach to three-dimensional concurrent engineering[END_REF]; [START_REF] Addo-Tenkorang | Concurrent Engineering (CE): A Review Literature Report[END_REF]; [START_REF] Tolouei-Rad | An approach towards fully integration of CAD and CAM technologies[END_REF]) and tools (e.g. [START_REF] Walcher | The customization 500 -An international Benchmark Study on Mass Customization and Personalization in Consume E-Commerce[END_REF] and [START_REF]Configurator Database. Configurator-Database[END_REF] for configurators), a process will be developed allowing the simultaneous generation of product design and reliable manufacturing data leading to a 50% reduction of "design to production" time of 50% and a 80% reduction of the time to market for new products development. Mini-factory Production System Model that can be easily and quickly instantiated in local green factories, and whose processes and machines can be driven directly by the formalized design process. This model represents the factory "to be" blueprints, its logistic structure and short JIT supply chain management approach that takes into consideration existing example of mini-factory (e.g. [START_REF] Jackson | Factory-In-a-Box -Mobile Production Capacity on Demand[END_REF]). It can be regarded as the basis for the "factory franchising" concept, where the manufacturing system can be instantiated locally with minimal production design effort. Thanks to this new system a 60% decrease in throughput time in production is expected as well as an increased ability to rapidly follow market by means of fast production and delivery of customised furniture. Reduced environmental impact because of no unsold or long term storage of products and reduction of work in progress thanks to smart order management and responsive supply chain are also interesting improvements from both economic and sustainable point of view.

Woodwork machining system able to empower the "Close to the Customer" concept. Main target is the development of a next generation woodworking system with high flexibility, high safety standards and ease of use with low production cost and low environmental impact, in particular for very small batches and JIT production, ultimately delivering very quickly to the customer. The system will be empowered by advanced HMI control and automatic machine set-up, and will then run continuously as in flow-like production. As the factory is meant to be instantiated "close to the customer", the machining system must specifically tackle issues such as dust extraction and noise control. Technological advances will allow the achievement of a reduction of CO2 emissions, lower training time and a safer working environment. A CTC Green Label in order to bring to customer awareness of the uniqueness and advantages of the production process, based on ISO 14955 extension to woodworking machines and on the FSC (Forest Stewardship Council), a certificate label will be developed. The label, also taking advantage of the development of a proper assessment model, is meant to be recognizable and unified, but still articulated and capable of highlighting local peculiarity.

The most challenging aspect of the CTC project is the need for a deep integration between the different modules that expose its multifaceted functionalities. The focus of the validation and demonstration activities will be therefore towards an effective integration of all CTC reference framework modules, because it is in their completed coordination that resides the success of the project. If any of the composing elements is innovative in of its specific characteristics, it is the coordinated effort for creating a much shorter production chain that really transforms the mini-factory into a major technological breakthrough. The success of the proposed production paradigm will be thus based on the exploitation of the above-mentioned innovations, but, above all, from the integration of all of them in an innovative business model delivering value through a local flexible manufacturing of green personalized products close to the customer. The economic potential of this concept lays in the possibility of instantiating several mini-factories all over Europe creating a franchising network.

3

The reference architecture

The foreseen functioning of a CTC mini-factory is introduced to give an idea of how the innovative elements will be interacting with each other to enable production and sale of sustainable and customized pieces of furniture close to the customers. The description tells how the CTC mini-factory will look like to a potential visitor once it will be running. Peculiarities of the CTC system at both factory and supply chain level are pointed out to provide an overview of what are the envisioned results upon project completion. A schematic representation of what is being presented is shown in Figure 1. The CTC mini-factory finds its ideal location in a shopping mall where both the sales area (CTC-shop) and the production area (CTC-factory) are located next to each other and are accessible by people visiting the mall. The CTC-system gets started when the Customer enters the CTC-shop and, with the support of a trained CTCoperator, customizes the furniture he/she is interested in using a user-friendly configurator. The design of furniture is driven by a parametric portfolio of products that has been predefined by CTC designers coherently with the functional constraints of the mini-factory. Once the furniture project (a single piece of furniture or a complete room) is finalized and the customer is satisfied with the offer, an order is generated and sent to the CTC-factory. Machine instructions are automatically created to command the behavior of the mini-factory. A real-time update of production data allows the customer to monitor the processing status of his/her order other than to increase the efficiency of the production system itself. A high level of integration of informative systems is one of the main features the CTC-system will rely on. In fact, a smooth flow of information from the idea generation to the production will allow a lean fulfillment of orders in short times. The details of the factory have to be carefully designed along with the supporting supply chain and material handling system. The idea is to have a short supply chain in order to favor the creation of a local suppliers base and to keep the level of inventories within the factory as low as possible. Raw material suppliers will be constantly managed by CTC mini-factory, coherently with short-term planning of the production, in order to grant adequate replenishment of stocks. Strong agreements with fast couriers are exploited for quick logistics. In so doing, a small inbound warehouse able to cover the needs of a few orders is enough. An automated warehouse will be set up in this place so that raw materials (panels) will be moved directly to the production line coherently with the production plan. At the end of the production line a packaging area is setup that will act also as outbound warehouse. So at this point the material is ready to be collected by local couriers for fast delivery to the customer. For the assembly phase, the idea of the project, is to leave the customer the possibility to choose between a specialized operator or the kit for Do-It-Yourself. Finally, it is worth of mention the attention that in the CTCsystem it will be paid to the waste management. Production waste has to be managed in a life-cycle conscious way, considering main potential way of treatment: re-cycled through direct agreement with raw material suppliers, burnt for energy generation, or sent to local landfills. To sum up it can be said that a compact and lean system is envisioned that will guarantee the achievement of excellent performance in terms of both customer service (short delivery time and high level of customization) and production efficiency. The design of a proper supply chain is important as well to reach this level of performance.

The CTC users

Complementary to the innovative modules of CTC, and taking into account that they become the principal interface between the mini-factory as a system on one side, and its users on the other one, a certain set of "CTC user profiles" has been defined. These roles have been selected as those strictly necessary for the good operation of the mini-factory. They are:

• The CTC-Furniture Designer, who will prepare the parametric product portfolio; • The CTC Customer, interacting with the mini-factory to obtain a customized furniture element; • The CTC-Shop Operator, interacting with the customer for the product design; • The Production Manager, supervising the whole mini-factory;

• The Stock Manager, specialized in managing inventory;

• The Mini-factory Operator, capable of operating the whole shop-floor;

• The Logistics Courier, to grant fast delivery of packages;

• The Supplier, to create a really short and integrated supply chain.

The term "user profiles" has been adopted because it is not conceived to represent the physical people who will interact with the CTC pilot, but the roles needed to make the factory work.

Impacts generated by the implementation of the concept

The basic idea of CTC is to move the factory directly where the customer is used to shopping: a green mini-factory is set up behind a glass pane in the shopping mall. The main target of the project is a customer segment with an average money availability who is willing to pay for a higher level of customization and who is aware of sustainability issues. The type of selected items and the location of the factory make the young and middle-aged people with children the most interested customers category. The pilot mini-factory will offer pieces of furniture for bedrooms for children and living rooms. The business model behind the diffusion of the CTC mini-factory is based on the idea that the same factory model is installed in shopping malls in different European countries. Local tastes and needs can be taken into account when the product is designed in the point-of-sale, yet the production system is a common one (not its supply chain, though). As a whole, expected benefits from the CTC project will have a significant impact on the European economy, also considering the high number of involved actors in the sector. Implementation of the CTC Mini-Factory will have a major impact on the wood furniture sector for both customers and manufacturers: the creation of a franchising network, for example, could reshape the traditional supply chain and leading to benefits not only in economic terms, but also from the sustainability perspective. The mini-factory is characterized by a set of machines and equipment strictly close to each other not only for the physical proximity, but also from the management point of view. The factory can work without work-in-progress since single orders are moved along the production system. The level of automation is high: the design software is linked with the production resources and the working instructions are automatically sent to machines that are reconfigured automatically with almost null setup times. The system thus works continuously avoiding time losses due to non-productive times -like queues or set ups-that are typical in the current production environment of this sector. The level of embedded technology is so advanced that in the best performing mini-factory a single operator is needed to run the whole system and he does not need to be skilled. In order for the operator to monitor the system, it will be possible to rely on a centralized control panel that do not requires specific knowledge of the single machine. Such configuration of the production system will allow the promising short delivery times (48 hours) and the offer of high level of level of customization.

The initial investment to set up one CTC mini-factory is expected to vary from a minimum of 330.000 Euro and a maximum of 580.000 Euro. In an IKEA shop, the price for a set of pieces of wooden furniture for a living room including TV and media furniture combined with storage units, a bookshelf, a desk and a coffee table could range approximately between 350 and 1900 Euro. A reasonable price for a living room offered under the CTC label should be around 2500 Euro.

A possible average price for a CTC bedroom for children including one single bed, a desk, one armoire with 3 doors, 2 shelves, a bookshelf and a chest of drawers could be set equal to 2000 Euro, whilst a rough estimation for a living room offered under the CTC label including TV and media furniture combined with storage units, a bookshelf, a desk and a coffee table should be around 2500 Euro.

A network of mini-factory

The CTC mini-factory finds its ideal location in the European shopping malls. The evolution of the European retail environment calls for more shopping centre space in the near future: it was estimated by Experian [START_REF]ESCT The importance of shopping centres to the European economy[END_REF] that the retail industry would have been the third fastest growing industry between 2005 and 2016 with an average growing rate of 2.6% per year. Considering both their current base and the developing potentialities, the malls can be considered as a fertile ground for the propagation of the CTC mini-factory production model in Europe. The selection of the location for installing the first mini-factories is crucial to get the expected results. Italy, UK and France are the best candidates: their high number of shopping malls [START_REF] Lambert | One step closer to a pan-European shopping enter standard[END_REF] is a proof that customers are more used to visit shopping malls and are probably more enthusiastic to experience shopping-related novelties.

In order to identify a reasonable numbers of mini-factories in the hypothetical franchising network that could make the business model a profitable and successful one, the main chains competing in the consumer "do-it-yourself" market sector at the European level have been used as a reference point (i.e. Bricocenter, Leroy Merlin, Obi center, Castorama). On the one hand, the production and delivery mode used by the CTC concept is unique: companies considered as competitors in terms of product types and volumes use different sale channels and their network structure couldn't represent a valid reference. On the other hand, the choice of basing the factory in the shopping mall makes it necessary to take into consideration features characterizing the retail world and their adaptation to the CTC concept. Using the specialized chains based on the "do-it-yourself" mode seems a good choice since, though their offer is based on catalogues, it could be assumed that their customers share some interests with the ones targeted by the CTC mini-factory. Customers who like the "do-ityourself" products pay attention to the sustainability aspect and are willing to spend time to choose single components and to put their own efforts to get the product that at the best fits with their needs. Considering the level of diffusion of the "do-ityourself" chains in Europe and assuming that the CTC mini-factory network will be, at least in the medium term, it is reasonable to assume that, in 5-year time, an overall number of 150-180 CTC mini factories will be operating in different European countries. The opening of an average of 30 centres per year is aligned with the expected efforts to install a new mini factory. The overall expected economic impact can be quantified approximately in 360 mln Euro of early turnover generated by a minifactory network of 150 units. This value corresponds to a 3% market share in value of the European market for the two segments of interest (bedrooms and living rooms). This esteem is likely to underestimate the business of the mini-factory since a smart capacity management policy could generate additional turnover by saturating the available capacity producing pieces of furniture for third parties. Widening the scope, a less easily quantifiable, yet important, business volume is induced in the supply chain. In this phase of the analysis it is not possible to provide precise values, but, for sure, it will contribute to amplify the CTC impact at the European level.

Conclusion

This paper first provided an overall understanding of a new paradigm in furniture production, based on the local flexible manufacturing of green personalized furniture close to the customer in terms of features offered (customization), place of fabrication (mini-factory in the shopping-mall), time to deliver (logistics arrangements), and cost (from customization to mass-customization). It then focused on the impact that such a paradigm will have on European economy once implemented. While still enduring fierce competition and relocation, Europe is nonetheless a major player in furniture on a global scale, where personalization and sustainability will represent a key strategy for its future development and success. Whereas the CTC paradigm is implemented and tested in the wood-working sector, the project consortium firmly believes that new business solutions meant to empower consumers as designers, manufacturers to produce in a distributed and small scale manner, and suppliers to be more flexible and demand-driven will be mandatory for most European industrial sectors.

Figure 1 :

 1 Figure 1: Reference architecture of the CTC mini-factory, and corresponding users.


Mohamed Mabrouk
email: mohamed.mabrouk@ims-bordeaux.fr

Severine Sperandio
email: severine.sperandio@ims-bordeaux.fr

Philippe Girard
email: philippe.girard@ims-bordeaux.fr

Stakeholder Mapping in a Collaborative Project for a Sustainable Development

Keywords: Sustainable Development, Corporate Social Responsibility, Stakeholder map

ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

More than one hundred definitions of sustainable development exist, but the most widely used one is from the World Commission on Environment and Development (1987): it states that sustainable development is a "development that meets the needs of the present without compromising the ability of future generations to meet their own needs" [START_REF]Report of the World Commission on Environment and Development[END_REF]. In the same way, Corporate Social Responsibility (CSR) is the implementation of sustainable development by companies: it represents the company's sense of responsibility towards the community in which it operates. In other words, a company has to increase its profitability and ensure its durability, but has to also consider the needs and interests of all its stakeholders in order to improve their economic, social and environmental performances. This research aims to establish a procedure for developing a stakeholder map for strategic projects in order to facilitate decision making of senior managers in a sustainable context: by taking into account needs and expectations of their partners early in the project, they can more easily ensure satisfaction and performance of these partners and therefore allow the success of the strat-egy. With this intention, the paper is organized as follows. In Section 2, general points of stakeholder theory and its impact on a collaborative project are introduced. In Section 3, we develop a methodology to create a stakeholder map in a collaborative project, with sustainable constraints. Finally, some conclusion remarks and discussions are provided in the last section.

What about stakeholder theory

The collaboration between stakeholders is decisive for the success of any project, particularly in the fields of Sustainable Development (SD) and Corporate Social Responsibility (CSR), where the taking into account of stakeholders' opinions is central in their guidelines. However, all stakeholders belonging to a same system share not necessarily the same concerns and have most of the time different and heterogeneous expectations and priorities. For this, the opportunity to identify and analyze the behavior of these stakeholders can change strategic directions of future development projects. What are the relationships between the different stakeholders? What relative influence do they have? Such an analysis enables the identification of institutions and relationships which need to be developed or dealt with to avoid negative outcomes and enhance positive ones [START_REF] Mayer | Stakeholder power analysis. Power Tools Series[END_REF]. Of course, the literature overflows with stakeholders' categorizations. The authors note that this theory contributes to understand projects by highlighting the importance of considerations of the stakeholders during planning, due principally to their influence on the project. It can also assist to classify the stakeholders as internal and external [START_REF] Clarkson | A Stakeholder framework for Analysing and Evaluating Corporate Social Performance[END_REF], primary and secondary [START_REF] Caroll | Business and Society: Ethics and Stakeholder Management[END_REF], according to they are immediately affected by, or can immediately affect the system. The major contribution about relationships between managers and stakeholders and the way to categorize them comes from Mitchell, Agle and Wood [START_REF] Mitchell | Toward a Theory of Stakeholders Identification and Salience: Defining the Principles of who and what really Counts[END_REF]. The authors tried to provide a dynamic model allowing to explain how a stakeholder should order its relationships. Their multi-attribute approach is based on three criterions allowing to categorize stakeholders on an organization: the power of the stakeholder to influence the organization, the legitimacy of the relationships in terms of desirability or appropriateness, the urgency (expectations of the stakeholder in terms of criticality and time-sensitivity). Such an analysis is very interesting, since the power or influence analysis between all the stakeholders is paramount in collaborative projects. However, we think that a simple classification is not sufficient when it comes to share and collaborate in the long term. Indeed, the theory does not give a clear guidance on how to exactly understand the settings and implementation, and dialogue aspects and consideration of stakeholders' expectations are not clearly identified. We decide to inspire from this approach to develop a model for applying stakeholder map for collaborative projects in order to support strategies and associated projects to be implemented. A certain focus is provided on sustainability issues. The model is based upon the audit of the different partners of a network in order to know their sustainable expectations and priorities, and their degrees of influence or dependency.

Aid to stakeholder mapping in a collaborative project, with sustainable issues

The performance of sustainable strategies depends in a large part to issues related to some actions to be implemented as: establish a constructive dialogue and a transparent communication with its stakeholders; share expertise with its partners; better determine the expectations from the various stakeholders; communicate its commitments and objectives with stakeholders; enhance the structure of the dialogue and adapt it to the needs of different issues. Thus, identify the stakeholders responsible for implementing and contribution of some objectives is a difficult and complex task. We also want to aid decision makings of senior managers by a procedure enabling to identify the "Sphere Of Influence" (SOI), which defines the scope of a company's social responsibility (ISO 26 000). We base this research on the actors' strategy and on the structural analysis [START_REF] Arcade | Structural analysis with the MICMAC method & Actors strategy with MACTOR method[END_REF], which are two methodologies enabling, by studying relations between the different elements of a same system (organization, network of companies …), to underline the variables that are essential to the system's evolution.

They have the advantage of stimulating reflection within a group, and leading it to think about certain aspects, which are sometimes counterintuitive. Our approach consists in laying down and analyzing the relations between stakeholders: it focuses on issues of sustainable development which represent stakes for the future and around which the actors could build their strategies. However, before beginning any project of development, a company has to know the involvement of its stakeholders and has to recognize stakeholders that can help or impede the completion of the project, depending of the impacts of this project on their own strategies: operational impacts (changes in operating activities), structural impacts (changes of capacities and / or competences of human and technical resources), functional impacts (integration of new technologies, modification of the supply chain, etc.). The associated computer tool is developed under Microsoft Visual Basic for Applications (VBA).

Stage 1: Strategic sustainable issues of the company and associated objectives

This stage, which is the least formal, is crucial: it allows to identify and analyze the strategic vision of the company by the selection of the objectives, for a sustainable development. This multi-objective vision of a sustainable development has been developed by John Elkington (notion of triple bottom line or Triple-P (People, Planet, Profit)) when he has defined sustainability as the balance between economic, social and environmental performances [START_REF] Elkington | Cannibals with Forks: The triple bottom line of 21st century business[END_REF]. Here, we consider generic objectives associated to these performances, but also the objectives associated to the performances of bearable aspects (intersection of the environment and the social), viable aspects (intersection of the environment and the economy) and equitable aspects (intersection of the social and the economy) (Table 1).

Table 1. Strategic objectives for a sustainable development

Stage 2: Relationships between the different stakeholders

In this stage, the different stakeholders (or actors) of a company for a project of sustainable development are identified. In this case, for example, we shall consider 6 actors (n=6: A 1 , A 2 …, A 6 ) corresponding to the customers, suppliers, subcontractors, banks, organisms, co-workers…, interacting with the company. The actor's strategy is also analyzed, as follows:

Matrix of Direct Influences (MDI).The matrix of Direct Influences is a square matrix of order 6 (Actors x Actors). It highlights the direct influences that each actor has on the others (Fig. 1). For each cell of the matrix, a score ''x i, j '' is assigned, depending to the influence that the row variable "i" has on the column variable "j". By definition, there is no impact of an Actor on itself (score = 0 when i=j). We will use for the different scores the values 0, 1, 2 and 3 (no influence, weak influence, medium influence, strong influence), so x i, j ϵ [0, 3].

Fig. 1. Matrix of Direct Influences (MDI)

Once the MDI matrix completed, we calculate the degrees of Direct Influences (DI) and Direct Dependencies (DD), for each Actor "A i ", as follows:

   n i j i j
x DD 1 , The scores assigned to the column for the A j [START_REF] Mayer | Stakeholder power analysis. Power Tools Series[END_REF] In this example, the Actor "A 2 " seems to be in a dominant position because it is the more influent (DI = 11), but it is also very dependent of the others (DD = 11). However, such a study doesn't enable to conclude on the actors' strategy in the network of partners because an actor can also influence other actors via transitional actors (this is the domino effect). Consequently, we cannot restrict ourselves to the analysis of direct influences, and the following paragraph focuses on the analysis of indirect influences between the different actors.

Matrix of Indirect Influences (MII).

The MII matrix allows considering indirect influences of each actor on the others. The MII i, j matrix, which analyses the impact of the Actor "i" on the Actor "j" via "n" other Actors, is obtained in "v i, j " as follows:

               n k j k k i j n n i j i j i j i MDI MDI Min MDI MDI Min MDI MDI Min MDI MDI Min V 1 , , , , , 2 2 , , 1 1 ,

Fig. 2. Synthesis

These to synthesis elements enable to know the stakeholders to be considered for future collaborations. However, considering that each project has its own characteristics related to one or several strategic objectives (cf. Table 1), they are not sufficient to build precisely the Sphere Of Influence since the positioning of the actors in relation to these objectives is not clarified.

Stage 3: Positioning of the actors in relation to the strategic objectives

Here we research the possible convergences and divergences of the different actors relative to the objectives of the project. Of course, they are different from one objective to another: it is also very important to collect the opinions of the different stakeholders in relation to each objective, in order to understand their positioning towards the project. The Matrix of Actors and Objectives (MAO, Fig. 3) shows this positioning according to a qualitative scale (-1, 0 and +1 corresponding to the fact that the actor is against, without opinion or favorable to the achievement of the objective).

  i i Supp DIN │ i
Opp │where i Supp is the support level of the Actor "i" (cor- responding to the sum of the positive scores assigned to the row of this actor) and i Opp is the opposition level of the Actor "i" (corresponding to the sum of the nega- tive scores assigned to the row of this actor). Moreover, the matrix enables to know the number of agreements and disagreements for each objective, which can be interesting information to help the decision making of managers.

Stage 4: Stakeholder Map

Here we propose a generic table including eight families of stakeholders, corresponding to the eight possible combinations between the three main attributes (DIN, DOI and DOD: see Table 2).

Table 2. Stakeholders Classifications

(1) The Dormant Stakeholders: they have no power (or a weak power) and are neither dependent nor involved (low level of the three attributes). They don't need a special attention and need only a minimum monitoring.

(2) The Dependent Stakeholders: They have a high level of dependency but low levels of influence and involvement (follower stakeholders). The existence of a contract with them leads to the necessity for the managers to follow their activities.

(3) The Influential Stakeholders: their interest for the project is low but they are powerful. No emergency action is requested because they aren't a part of the project, but managers must satisfy their possible requirements.

(4): The Influential and Dependent Stakeholders: they are both powerful and dependent. They have their own ways to carry out their projects, but are also influenced by the actions of the other stakeholders. Such a category of actors has to be seriously monitored.

(5) The Interested Stakeholders: They have a high level of involvement but are neither influential nor dependent. They can't engage a pressure on the company but it's necessary to keep them informed since they can be considered as potential collaborators (for example: associations, consulting firm).

(6) The Involved and Dependent Stakeholders: they are involved but dependent. They aren't powerful (subcontractor for example): they also can't engage pressures on the company, but it's necessary to inform them for any progression in the project. [START_REF] Elkington | Cannibals with Forks: The triple bottom line of 21st century business[END_REF] The Dominant and Involved Stakeholders: they are both powerful and interested in the project. Their cooperation is essential to ensure the feasibility of the project.

(8) The Primordial Stakeholders: they are powerful, interested in the project, and dependent. Managers are obliged to establish a privileged relationship for responding to their needs and expectations.

We will consider that the Sphere of Influence to be considered for a project includes all the actors interested in the project and can help its completion: these are the categories ( 6), ( 7) and (8).

Conclusion

Stakeholder theory has its roots from management literature and was developed as a response to the needs to successfully carry out strategic processes in the context of Here, the approach of stakeholder analysis has been completed and oriented towards sustainable development issues. The existence of an approach that allows collecting different opinions and strengthening the dialogue between the different stakeholders is critical to a long-term success. Resource managers can thus intervene in the interest of development and improvement of future projects, in order to re-evaluate the strategic objectives initially set, revise the different contracts with stakeholders, regularly maintain and update the different classes of stakeholders. In this paper, we have tried to overcome many limits related to stakeholder theory and have created a model for decision making in a collaborative and sustainable context: this model enables to identify the stakeholders with whom it is recommended to collaborate. The purpose is also to build the strategies to be implemented, taking into account the expectations of the different stakeholders, in order to ensure the satisfaction of these partners and therefore allow the success of future collaborations. Our work has demonstrated its ability to not only contribute to select suitable stakeholders, but also provide a guide to strategic management for sustainable development issues. However, we cannot neglect some weaknesses of this theory which can be ambiguous and subjective. Indeed, the categorization process depends on the evaluators and their analysis can be influenced by their backgrounds, environment or people involved in the process. It is also subject to indirect aspects such as honesty and reliability of the collected information.

SH Mapping Attribute (1) (2) (3)

1 , 1 , 4 )

 114 j k  . Thus, the degrees of Indirect Influences (InI) and Indirect Dependencies (InD), for an Actor "i", are: The scores assigned to the row for the A i The scores assigned to the column for the A j (Synthesis. At this point, managers have the possibility to weight the different degrees (degrees of Direct and Indirect Dependencies and degrees of Direct and Indirect Influences) according to their knowledge about the market (Fig.2). Then, two synthesis elements are calculated: the Degree of the Overall Influence (DOI) corresponding to the weighted average of direct and indirect influences, and the Degree of the Overall Dependence (DOD) corresponding to the weighted average of direct and indirect dependences.

Fig. 3 .

 3 Fig. 3. The MAO matrix


Günther Schuh
email: g.schuh@fir.rwth-aachen.de

Christian Fabry
email: christian.fabry@fir.rwth-aachen.de

Philipp Jussen
email: philipp.jussen@fir.rwth-aachen.de

The Influence of the Customer in Service Production

Keywords: Service production, productivity, characteristic curves, customer productivity, external factor

ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

Due to an increase in competition and the need to generate additional value for the customer the manufacturers of tangible goods expand their portfolio with supplementary industrial services thus creating innovative product-service-system [START_REF] Baines | State-of-the-art in product-service systems[END_REF]. Increasing operational productivity for these Product-Service-Systems is different from regular production of tangible goods due to the characteristics of services. The intangibility of services [START_REF] Frietsche | Dienstleistungsproduktion[END_REF] and the interaction with the customer [START_REF] Meier | Industrial Product-Service Systems -IPS2[END_REF] require a separate set of management concepts [START_REF] Grönroos | Service Productivity. Towards a conceptualization of the transformation of inputs into economic results in services[END_REF]. This paper focuses on the interaction with the customer and the customer's role as an external production factor in productservice-systems. Due to the integration in the service production process the customer has a determining effect on the productivity of the process. The customer can bring himself or an object in his possession as an external production factor into the process [START_REF] Haller | Dienstleistungsmanagement. Grundlagen -Konzepte -Instrumente[END_REF]. The involvement of the customer can range from a passive role regarding the provision of own production factors to an active participation in the production process [START_REF] Fitzsimmons | Service Management[END_REF]. Thus the external factor can have different characteristics, which can be differentiated into tangible good, immaterial good and human participation [START_REF] Frietzsche | Externe Faktoren in der Dienstleistungsproduktion[END_REF].

Tangible goods appear as mobile or immobile goods of the service customer. They are objects in the possession of the customer. From a production theory point of view the juridical component is sometimes considered not relevant. But the inability for the service provider to freely dispose makes it a matter of productivity as the timely and locally correct disposal determines duration of the service delivery process and therefore is an important factor in the consideration of service productivity [START_REF] Frietzsche | Externe Faktoren in der Dienstleistungsproduktion[END_REF]. Immaterial goods can be information, risks or patents. They can be an important factor in the planning and control of a service production process. The human participation describes the case when division of labor between the provider and the customer exists and the customer is integrated in the service production process as a co-creator [START_REF] Dunkel | Interactive Work: A Theoretical and Emipircal Approach to the Study of Service Interactions[END_REF]. In Product-Service Systems, the external factor usually is a combination of the three types. Fig. 2. Intensity of integration of the customer in service production [START_REF] Meffert | Dienstleistungsmarketing. Grundlagen -Konzepte -Methoden[END_REF] The service production requires a synchronous concurrence of the internal and external production factors [START_REF] Frietsche | Dienstleistungsproduktion[END_REF]. The intensity of integration, sometimes defined as customer integration level, describes how far the external factor is involved in the production process of a service [START_REF] Kleinaltenkamp | Der Kundenintegrationsbegriff im (Dienstleistungs-)Marketing[END_REF]. There are two different development paths to diversify the intensity of integration for the service provider (figure 3). On the one hand there is the possibility to outsource tasks and activities of the service production to the customer (externalization), on the other hand the service provider can carry out other tasks and activities from the customer (internalization). The flexibility of changing the customer's intensity of integration is limited. Reasons for this are that quantitative and qualitative resource capacities on both sides are limited and that the execution of the service requires a minimum activity on both sides [START_REF] Meffert | Dienstleistungsmarketing. Grundlagen -Konzepte -Methoden[END_REF].

For the service production process different characteristics and features of the external factor have an impact on the productivity. The ability to dispose the external factor describes to what extent the service producer can autonomously access the external factor. The external factor can remain in the command of the customer or switch to the command of the service provider during the production. If the external factor remains in command of the customer timing and synchronization between the consumer and the provider is required. If the external factor changes to the area of disposition of the service provider, the provider can arrange the external factor autonomously. Closely related to the ability to dispose the external factor is the ability of the service provider to control the time window for the service delivery. The customer can set dates for access to the external factor or for the interaction in the service production process, if these are necessary requirements for the customer. This limits the freedom of action for the service provider. A typical case is a time critical repair service. If there are no restrictions on customer side for the date of the service provision, the customer can specify a time window or can get a time slot from the provider. An example for this case is a maintenance service, if the customer does not specify a date, but only a time window for the procedure.

The localization of the external factor describes the accessibility of the external factor. Immobile external factors are characterized by their dependency on a location. In combination with the requirement to involve the external factor in the service production process, this leads to a service provision at the site of the external factor. Mobile external factors are characterized by their ability to vary their location. A special type of mobile external factor exists, if the access to the factor can be done virtually anywhere. An example for this is typically information.

The need of the areal coincidence describes if service provider and customer must come together for production. A differentiation can be made between located and separated services [START_REF] Kulke | Wirtschaftsgeographie. 5[END_REF].

The knowledge of the service provider of detailed features of the external factor and the knowledge of the current state at the beginning of the service production process can vary. In the best case the service provider has detailed information to describe the external factor and its current state before the actual provision. In reality however, the characteristics and the current state of the external factor are typically only partially known in advance or become clear during the service delivery [START_REF] Fitzsimmons | Service Management[END_REF].

In summary the following features can be differentiated:  Type of external factor: Human; Object; Information  Type of integration: passive; access of the external factor; Co-Production  Ability to dispose: deadline by customer; matching of a time window the customer; autonomously by the service provider  Local dimension and accessibility: immobile; mobile; independent of location  Areal coincidence of customer and service provider: necessary; not necessary  Information about the external factor: completely available; partly available; get clear during the provision

Methodology

In order to research the influence of the external factor in the service-production process a system theory approach is taken in order to create a simulation model. System theory is used for modeling relationships in complex organizational structures such as productions systems [START_REF] Wiendahl | Betriebsorganisation für Ingenieure[END_REF]. System dynamics is used as simulation method. The system dynamics methodology is specifically suitable to explain behavior system by analyzing the structure of cause-effect relationships between the system elements. On the basis of delayed or back coupled effects non-linear or counter-intuitive system behavior can be modeled, simulated and analyzed [START_REF] Oliva | Developing operational understanding of service quality through a simulation environment[END_REF]. A holistic model for service production was created. The simulation model was validated with respect to its structure, the parameters and the model behavior [START_REF] Fabry | Service Excellence durch Lean Services[END_REF]. The validation with respect to structure and parameters was conducted in workshops with experts from research and from the industry. In order to evaluate the model behavior a sensitivity analysis and extreme-conditions tests were conducted. The validation showed that the developed system-dynamic model is robust and suitable for the stated problem. The part which concerns the external factor is introduced in detail in this paper.

Fig. 3. Simulation Model for the performance potential of the external factor

From the perspective of the service producer the activities of the customers, which are connected to the internal activities of the service producer and its internal production factors, are relevant to the production process. Autonomous activities of the customer are beyond influence of the service provider. For the production process it is only relevant that the required performance potential of the external factor is available and whether the activities were carried out as previously intended.

The build-up performance potential of the external factor arises from the amount of pending work orders, the integration intensity as well as the planned capacity reserve of the external factor. The pending work describes the within the next time period generally pending activities. The pending work is the sum of the work still in process plus the newly released work orders. The integration intensity is a factor for the degree of contribution of the external factor to the service provision.

The co-producing external factor can accumulate for a smaller or bigger share of the work. The integration intensity ultimately is the ratio of amount of work between the service provider and the external factor. The reserve capacity reflects the fact that the customer anticipates deviations in required potential during the service production process and holds available additional capacity.

Build-up performance potential = (New work orders + work in progress) * integration intensity * capacity reserve

The performance potential of the external factor is used in the course of the production of services to combine with the capacities introduced by the service provider and add value. The use of performance potential results from the amount of processed work in general. The specifically retrieved potential of the external factor is proportionally dependent on the degree of integration.

Use of performance potential = processed work * integration intensity

If there are deviations in the service production process, this may lead to more or less work compared to what was planned. In the first case this requires the provision of additional performance potential to fully perform the required work performance. This additional requirement is manifested in the fact that the originally planned capacity is not sufficient to complete the activities. This additionally required performance potential can be described mathematically as follows:

Additional performance potential = IF (performance potential < 0) THEN (performance potential) ELSE (0)

If the buildup performance potential of the external factor is not used until the end of the time period, it deteriorates. The reasons for the deterioration can be an incorrect sizing of the performance potential and variations in the service production. In order to calculate the performance of the external factor, the unused performance potential is kept track of but will not be described further mathematically.

The level of performance is (amongst other factors which are not debated in this paper) a determining factor of the processed work of each time period. The type of integration of the external factor can be the provision of information, the provision of access or co-production. If the integration of the external factor includes only the provision of information or the granting of access to an object in the possession of the customer, the level of performance of the external factor is assumed constant. An impairment of service production due to inadequate information or limited accessibility manifests itself in a disposition related error or hold-up and thus leads to interruption or slowing of production. In the case of co-production it is assumed that the external factor mainly consists of human workforce. The performance level of staff is determined by the factors performance conditions, performance requirements, performance ability and motivation. These factors are assumed constant but can be varied and adapted for a specific organization.

The ability to dispose the external factor describes the extent to which the service provider can influence the customer to confirm the date of service provision. By controlling the amount of work orders the ability to dispose indirectly determines the amount of work in a specific time period. The service production planning and control algorithms distribute the amount of work over different time periods in order to achieve a constant degree of capacity utilization. If there is no ability to dispose the external factor, i.e. there is a fixed period for the service production, the fluctuations of the amount of work will be bigger over different time periods.

Results and discussion

The system-dynamic model reveals the influence of external factors on the service production performance. In order to generate the results simulation runs were conducted in each of which the set-up of the parameters of the simulation model was kept constant, expect for one parameter. The parameters varied were intensity of integration, ability to dispose the external factor and the capacity reserves of the external factor. For each value of the parameters the resulting averages for the target variables were calculated over the time periods. In order to illustrate the effect of the parameter changes, the dependent target variables capacity utilization and adherence to delivery dates were used. By plotting the parameter on one scale and the resulting target variable on the other a characteristic curve is obtained (see figure 5).

With increasing intensity of integration of the external factor, the influence of the customer on the service production process increases. This results in increased process interferences, which leads to fluctuating process durations. Accordingly the utilization of the internal resources of the service provider decreases with the increasing influence of the customer. When the customer only provides information, the integration and influence of the external factor is limited. The influence on the production process increases when the customer has to grant accessibility. In a scenario of co-production the influence of the external factor is largest.

With an increase in ability to dispose the external factor the utilization of the internal resources of the service provider increases. When the service provider has only a slight possibility of coordinating the point of service production with the customer, not all work orders can be started on time. This leads to a poorer utilization of the service production system. This effect is enhanced in the presence of a high proportion of short-term work orders, which must be either served at the time or rejected.

The customer impacts the performance of the service production system with his own capacity reserves. The capacity reserves serve as a type of safety buffer for unforeseen events or complications in the service production. Increasing the capacity reserves of the external factor helps to deal with those disturbances and therefore increases the adherence to delivery dates. However the effect on the utilization of internal service production resources is inconclusive and greatly depends on the outline of other production parameters.

Conclusion

This paper discussed and characterized the customer in service production systems as an active part in service production. A simulation model was used in order to further investigate the effects and illustrate cause-effect relationships using characteristic curves. Two major implications can be derived from this research. First because of the immateriality and the lack of storability service production systems are especially prone to utilization issues. Maintaining a constant degree of capacity utilization in order to maximize productivity therefore is a key management challenge. Secondly it is evident that to ensure high performance of the service production system the relevant parameters of influence have to be tuned together with the customer. With respect to existing research on the topic, this paper shows the effects of the customer as an external production factor in service production for the first time using characteristic curves. Further research may include finding a way to parameterize the curves in mathematical equations, so that the concept can be applied to specific practical use cases in order to find optimal solutions.

Fig. 1 .

 1 Fig. 1. Service Input/Output Model[START_REF] Sampson | The Unified Service Theory. A Paradigm for Service Science[END_REF]

Fig. 4 .

 4 Fig. 4. Characteristic curves for the influence of the external factor in service production

The Customer as an external Factor in Production-Service-Systems"Services are production processes wherein each customer supplies one or more input components…"[START_REF] Sampson | The Unified Service Theory. A Paradigm for Service Science[END_REF]. The service customer therefore is characterized by being part of the service production process[START_REF] Frietsche | Dienstleistungsproduktion[END_REF]. This is illustrated in figure1.

Acknowledgements

The research presented in this paper was partly developed in the work of the research project SERVSYNC. This project is sponsored by the AiF under the program for the promotion of industrial research and development (IGF) by the Federal Ministry of Economics and Technology under the number 17743 N.